Farm Waste Management and Disposal Systems 9789698237981

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Managing Editors Iqrar Ahmad Khan and Muhammad Farooq

Farm Waste Management and Disposal Systems

Abdul Nasir Awan Faizan-ul-Haq Khan

University of Agriculture, Faisalabad, Pakistan i

Abdul Nasir Awan Faizan-ul-Haq Khan Department of Structures and Environmental Engineering University of Agriculture Faisalabad Pakistan

ISBN 978-969-8237-98-1

© University of Agriculture, Faisalabad, Pakistan 2017 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts about reviews or scholarly analysis or material supplied specifically for being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher’s location, in its current version, and permission for use must always be obtained from the University of Agriculture, Faisalabad, Pakistan. Permissions for use may be obtained in writing to the Office of the Books and Magazines, University of Agriculture, Faisalabad, Pakistan. Violations are liable to prosecution under the respective Copyright Law. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein.

Foreword The digital age has its preferences. The reading time has been encroached upon by a watching time. The access to information is easy and a plenty where Wikipedia has emerged as the most powerful encyclopedia ever. Yet, a book is a book! We wish to promote the habit of reading books. Finding books is not difficult or expensive (www.pdfdrive.com) but a local context and indigenous experiences could be missing. The University of Agriculture, Faisalabad (UAF) has achieved global rankings of its flagship programs and acceptance as a leader in the field of agriculture and allied sciences. A competent faculty, the stimulating ecosystem and its learning environment have attracted increasing attention. Publication of books is an important KPI for any institution of higher learning. Hence, UAF has embarked upon an ambitious ‘books project’ to provide reference texts and to occupy our space as a knowledge powerhouse. It is intended that the UAF books shall be made available in both paper and electronic versions for a wider reach and affordability. UAF offers more than 160 degree programs where agriculture remains our priority. There are about 20 institutions other than UAF who are also offering similar degree programs. Yet, there is no strong history of indigenously produced text/reference books that students and scholars could access. The last major effort dates back to the early 1990’s when a USAID funded TIPAN project produced a few multiauthor text books. Those books are now obsoleted but still in demand because of lack of alternatives. The knowledge explosion simply demands that we undertake and expand the process anew. Considering the significance of this project, I have personally overseen the entire process of short listing of the topics, assemblage of authors, review of contents and editorial work of 29 books being written in the first phase of this project. Each book has editor(s) who worked with a group of authors writing chapters of their choice and expertise. The draft texts were peer reviewed and language corrected as much as possible. There was a considerable consultation and revision undertaken before the final drafts were accepted for formatting and printing process. This series of books cover a very broad range of subjects from theoretical physics and electronic image processing to hard core agricultural subjects and public policy. It is my considered opinion that the books produced here will find a wide acceptance across the country and overseas. That will serve a very important purpose of improving quality of teaching and learning. The reference texts will also be equally valued by the researchers and enthusiastic practitioners. Hopefully, this is a beginning of unleashing the knowledge potential of UAF which shall be continued. It is my dream to open a bookshop at UAF like the ones that we find in highly ranked universities across the globe.

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The Department of Structures and Environmental Engineering has compiled this useful book on the disposal of mismanaged vegetative-, animal-, domestic-, industrial- and human waste in the rural areas. The disposal systems offer an opportunity to add value by producing energy and fertilizers while improving environments. This book will certainly be a valuable reading for the scholars and engineers. Before concluding, I wish to record my appreciation for my coworker Dr. Muhammad Farooq who worked skillfully and tirelessly towards achieving a daunting task. Equally important was the contribution of the authors and editors of this book. I also acknowledge the financial support for this project provided by the USDA endowment fund available to UAF.

Prof. Iqrar A. Khan (Sitara-e-Imtiaz) Vice Chancellor Unviersity of Agriculture, Faisalabad

Preface Despite open land scape in villages, the people suffer from several diseases due to poor sanitary conditions. The poorly planned housing and drainage system, mismanaged disposal of vegetative, animal, domestic, Industrial and human waste are the chief contributing factors to rural pollution. To ensure better sanitary conditions and promotion of general health of the people living at the farms, properly collection of refuse, suitable system for its transportation and safe economical disposal are basic requirements in the rural areas. The appropriate waste management system will also be helpful in the proper use of waste materials for the energy generation, raw material for the industries and manure for agricultural lands. Disposal of rural and urban waste has been a problem since ancient time. With industrial development and rapidly growing population in the cities and villages, some efforts have been made to maintain and enhance the environmental quality though control on industrial pollution and disposal of urban and rural wastes. Proper disposal of rural waste is completely ignored if rural management is concerned. However, looking to the availability of considerable quantities of wastes from crops, animal and human habitants, problem needs to be addressed carefully for the development of alternative methods and processes for management and disposal of rural wastes. Management and disposal of farm waste cannot be segregated from each other. However, farm waste management can be defined as the discipline associated with the control of generation, storage, collection, transfer and transport, processing and disposal of wastes in a manner that is in accordance with best principles of public health, economics, engineering, conservation, aesthetic and other environmental considerations. Farm waste management includes all administrative, financial, legal planning and engineering functions involved in the whole spectrum of solution to problems of waste caused thrust upon the community by its inhabitants. In the present days, the problems associated with farm waste management are complex because of the quantity and diverse nature of the wastes, funding limitation, impact of technology and lake of social awareness amongst the rural community. This book has been divided mainly into eight chapters. Chapter-I is about the brief Introduction of urban and rural wastes, definitions, various sources of generation, different terminologies used and different questions being asked from public health engineers, scientists and all others from the public sectors. Chapter-II Is about the Necessity of Rural Waste Management and Disposal System, Chapter-III is about the Rural Waste Characterization. Chapter-IV is about the rural waste which includes Agricultural and Plant Waste (leaves, stalks, stubbles and shells etc.), Chapter-V is based on Rural Waste from Animals and Chapter-VI is based on Animal Byproducts (animal excreta, byproducts of dead animals, effluent classification, manure management and disposal as Bio-gas production with its physical and chemical properties). Chapter-VII is consisting of Domestic Waste and Chapter-VIII v

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encompasses the Rural Industrial Waste Management and Disposal Systems. Various methods of waste collection and disposal at domestic and rural industrial level (treatment of domestic waste, rice mill, gur industry byproducts of leather industry) are very rarely applied in rural areas of Pakistan. Rural industrial wastes are not mostly considered and as such they do not pose any severe threat in disposal and management. Presently most of these wastes are either underutilized or unutilized. Methods of handling, treating and disposing of waste may adversely affect air, water and soil quality to all those dwellers nearby. Therefore, if proper methods of disposal are followed then sanitary conditions can be maintained and some economic returns can also be gainfully achieved. The sincere intention of the authors is to present a book which will be very useful text book and can be used as quick reference book for the students pursuing to study a course on Farm Waste Management and Disposal Systems, Bio-Waste Management, Bio-fuel and Bio-Energy Systems. This book is written in accordance with the aims and objectives of the course curricula approved by Higher Education Commission. The book will be very useful for students, scientists, scholars, researchers and engineers in the discipline of agriculture and allied sciences, agricultural engineering, environmental engineering, food engineering, energy resource engineering, civil and public health engineering, dairy and farm managers, research and extension workers engaged in the field of bio-energy, rural industries and rural sanitation. The book deals with the summery of various disposal systems of plant, animal, and animal byproducts, domestic and rural industrial waste generated in the rural areas, both from sanitary and economic point of view. There is no doubt in writing that rural waste can be used as a source of energy and a raw material for industries, may be big or small, and as a source of manure for agricultural lands. However, some efforts have been made to suggest cheap and simple technologies for the disposal of rural waste. Therefore, it is believed that this book will increase the knowledge and understanding of the reader. Abdul Nasir Awan Faizan-ul-Haq Khan

Chapter 1

Introduction Faizan ul Haq Khan*

Abstract The population of Pakistan is growing at alarming rate in the urban and rural areas of Pakistan. Rural areas are still unplanned and undeveloped creating a lot of health problems and issues. The villages are completely ignored as far as rural waste management and disposal system is concerned. A waste is considered as “a matter in the wrong place”. Waste may be considered as damaged, defective or superfluous material produced during manufacturing process, discarded material from agriculture and forestry. All those materials at wrong place can be segregated, transferred, recycled and reused with great financial and environmental benefits. Presently waste management and disposal philosophy is to collect, store, process and treat all waste as resource material for recycling, conversion to manure and as a source of energy. However, if domestic and industrial wastes are considered, they are disposed of purely from sanitary point of view. Therefore, some efforts have been made to suggest appropriate, cheap and simple techniques for waste management and disposal systems, keeping in view the energy generation, raw materials for the industries and manure for agricultural lands of Pakistani villages. Keywords: Farm waste, Rural waste, Urban waste, Solid waste, Industrial Waste.

1.1.

Introduction

Disposal of rural and urban waste has been a problem since ancient time. Despite open land scape in villages, the people suffer from several diseases due to poor sanitary conditions. The poorly planned housing and drainage system, mismanaged

* Faizan ul Haq Khan Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. For correspondance: [email protected]

Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

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disposal of vegetative, animal, domestic and human waste are the chief contributing factors to rural pollution. To ensure better sanitary conditions and promotion of general health of the rural community living at the farm, properly collection of refuse, suitable system for its transportation and safe and economical disposal are basic requirements in the rural areas. With industrial development and rapidly growing population in the cities and villages, some efforts have been made to maintain and enhance the environmental quality though control on industrial pollution and disposal of urban and rural wastes. The rural areas are completely ignored whereas proper management and disposal of rural waste is concerned. The nature, proportion and methods of utilization of wastes differ widely from place to place. Every farm with waste products requires a waste management system. Almost every farm is unique in its combination of waste production, handling, storage, treatment and disposal. The domestic wastes consisting of solid waste, sludge and human excreta are very rarely disposed off properly in rural areas of Pakistan. Rural industrial wastes are not considerable as they do not pose any severe threat in management and disposal. However, regarding the availability of considerable quantities of wastes from crops, animal and human habitants, these can be disposed off either by recycling or by discharge. This problem needs to be addressed carefully and close attention is required to develop an alternative methods and processes for management and disposal off these wastes. Therefore, the appropriate waste management and disposal system will also be helpful in the proper use of waste materials for energy generation, industrial raw material and manure for agricultural lands.

1.2.

Definitions of Waste

Normally a waste is considered as “a matter in the wrong place”. However, waste may be defined as the damaged, defective or superfluous material produced during manufacturing process, discarded material from agricultural and forestry, refuse available from the places of human and animal habitation, which are allowed to escape without utilizing or are utilized on the site. Waste materials are always considered as a material that is cheaper to throw than to store for use. Waste is no longer considered as unwanted to be dumped out of site. Therefore, all material at wrong place can be segregated, transferred, recycled and reused with great financial and environmental benefits. Solid wastes are all the wastes arising from human and animal activities that are normally discarded as useless or unwanted. Because of their intrinsic properties discarded waste materials are often reusable and may be considered a resource in another setting. Any waste that does not go up “the stack/waste dump” or down the drain is known as waste. Solid wastes are useless, unwanted, discarded materials of production or consumption and are not free flowing. All those materials which are generated at time of production and at time of consumption or utilization are known as waste material. Therefore, a material becomes waste only when it has ceased to be useful in the process and on the site where it is produced. No doubt that these wastes have high values in terms of energy, industrial raw material or manure. For example,

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night soil from house hold, animal dung and refuse are the materials available to the owners of biogas plant for production of methane and manure. Currently waste disposal philosophy is to treat all waste as resource material, some for recycling, some for conversion to manure and some as a source of energy.

1.3.

Impacts of Solid Wastes on Environment

Unless properly managed, solid wastes have potential of serious impacts on environment. It can lead to surface and ground water contamination, land pollution and air quality deterioration. Figure 1.1 shows the likely sources of impacts on air, water and land/ soil environment. Water infiltrating through the wastes generates leachate, which can ultimately mix with the ground water. Dust and litter scattered by wind are responsible for deterioration of air quality in the vicinity of disposal sites. Insanitary method of disposal of wastes also produces odor and affects the aesthetics of the area. Moreover, decomposition of wastes releases obnoxious gases posing high risk and threat to human health. Some of the environmental and health hazards due to solid wastes are presented in Table 1.1, given below; Table 1.1 Some environmental hazards due to solid wastes Type

Hazard

Environmental Pollution

Air, water and land/soil quality deterioration, high levels of noise, poor aesthetics

Diseases

Gastrointestinal disorders, jaundice, diarrhea, respiratory infection, dermal diseases, etc., and may even cause cancer

Injury

Injuries to workers by sharps, glasses, and chemically aggressive substances present in the wastes.

Source: Alemayehu (2004)

Environmental impacts of poorly managed wastes have been studied all over the world. It is now well known that many disease vectors and water borne diseases spread due to poor collection and disposal practices of solid wastes. Most environmental impacts can be minimized by employing appropriate techniques of urban/rural solid wastes management. Solid waste collection by government owned and operated services in Pakistan's cities currently averages only 50% of waste quantities generated; however, for cities to be relatively clean, at least 75% of these quantities should be collected. To achieve this level, a large capital investment is required. Demand for services will grow as urban populations grow and as per capita waste generation rates grow; the latter is projected at one to three percent per year.

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Fig. 1.1 Typical Sources of Environmental Impacts Due to Solid Wastes Table 1.2 Province wise population and rural/urban Area Pakistan Rural Urban NWFP Rural Urban FATA Rural Urban Punjab Rural Urban Sindh Rural Urban Balochistan Rural Urban Islamabad Rural Urban

Households (million) 19.701 13.450 6.250 2.301 1.889 0.411 0.357 0.347 0.009 10.718 7.444 3.274 5.170 2.911 2.258 1.018 0.814 0.204 0.136 0.043 0.092

Population (million) 193.392 129.572 63.819 17.554 14.581 2.973 3.137 3.054 0.083 72.585 49.885 22.699 29.991 15.329 14.661 6.511 4.995 1.516 0.799 0.274 0.524

Source: Population Census of Pakistan (1998), World Population Review (2016)

The increased quantity of waste will also place greater demands on disposal services, thereby exacerbating an already poor situation since present disposal methods for

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solid waste are totally inadequate. Disposal is by open dumping, primarily on flood plains and into ponds, causing significant environmental damage. Unfortunately, none of the cities in Pakistan has a proper solid waste management system right from collection of solid waste up to its proper disposal. Much of the uncollected waste poses serious risk to public health through clogging of drains, formation of stagnant ponds, and providing breeding ground for mosquitoes and flies with consequent risks of malaria and cholera. In addition, because of the lack of adequate disposal sites, much of the collected waste finds its way in dumping grounds, open pits, ponds, rivers and agricultural land. Environmental degradation is not only well advanced already, but also is getting progressively worse as the country's population, urbanization and industrialization increase, and as its economy develops generally. According to the World Population Review (2016), of the 193.392 million persons living in Pakistan, 67% live in rural areas, while 33% live in urban areas (Population Census of Pakistan, 1998) (Table 1.2). Furthermore, out of 33 % of persons living in urban areas, 54 % of them live in ten major cities of Pakistan, shown in Table 1.3 below; Table 1.3 Population of Ten major cities of Pakistan City Karachi Lahore Faisalabad Rawalpindi Multan Hyderabad Gujranwala Peshawar Quetta Islamabad

Households (million) 1.436 0.740 0.278 0.220 0.162 0.178 0.151 0.149 0.074 0.092

Population (million) 11.624 6.310 2.506 1.743 1.437 1.386 1.384 1.218 0.773 0.601

Source: Population Census of Pakistan (1998), World Population Review (2016)

During the last several decades, migration has occurred from rural to urban areas. The chief factors responsible for this migration are: slow progress in the agriculture sector, low crop yields, lack of alternate employment opportunities and environmental degradation due to water logging/salinity, deforestation and desertification. The large rural influx has, in turn, contributed to the overburdening of urban infrastructure and urban services. There has not only been a rapid decline in the quality and availability of basic urban resources and amenities, such as housing, potable water, transportation, electricity, gas, drainage and sewage but also mushrooming of katchi abadis (squatter settlements), often located on the most marginal land. Today, squatter settlements account for about 25 to 30% of Pakistan's overall urban population. The municipal institutions do not have sufficient resources and technical capacity to accommodate the needs of increasing urban population. The poor communities residing in urban settlements are often engaged in several initiatives on self-help basis, e.g., solid waste management and recycling. Almost all the paper, plastic, metals and glass are collected and re-used/recycled. Thus, the poor

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communities in urban settlements play a key role in waste recycling. The only waste which remains on streets and collection points is the organic waste. This could be used for making compost but neither the municipalities nor rural areas has moved towards full utilization of this business.

1.4.

Estimated population and household in big cities of Pakistan

The number and growth of population and households is the foremost factor affecting the solid waste and its management at various stages. According to a study (Data collection of national study on privatization of solid waste management in eight cities of Pakistan, 1996) conducted by Engineering Planning and Management Consultant during 1996, the selected cities are growing at a growth rate from 3.67% to 7.42% which is much higher than the overall growth rate of Pakistan, i.e. 2.8%, Major cities of them are estimated to double their population in next ten years (Table 1.4). These cities are generating high amounts of solid waste which is increasing annually with the respective population growth. Table 1.4 Population Estimates (000's) Sr. No. 1 2 3 4 5 6 7 8 Total

Cities Gujranwala Faisalabad Karachi Hyderabad Peshawar Bannu Quetta Sibi

Census 1981 601 1,104 5,208 911 717 48 286 28 10,884

1996 1,759 2,364 10,522 1,733 1,655 82 1,000 60 21,171

Estimated 2006 3,598 3,928 16,816 2,661 2,403 118 2,004 100 33,634

2016 7,361 6,528 26,873 4,085 3,489 169 4,017 166 54,704

Source: EPMC (1996), Mahar et al. (2007), Iqbal et al. (2015)

The numbers of households also play an important role in generation and collection of the solid waste. The average household size in the selected cities varies from 6.7 to 7.3 persons. Table 1.5 shouls size and number of households in each of the selected cities.

1.5.

Types and Sources of Different Wastes

Wastes include all types of solids, semi-solids and liquid materials that the possessor no longer consider of sufficient value in urban/rural areas to retain (Figure 1.2). Knowledge of the type and sources of solid waste along with data on the composition and rate of generation is a basic for design and operation of functional elements associated with solid waste management.

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Sources of Solid Waste

Sources of solid waste in an urban and rural community are in general, related to land use and zoning. Urban and rural sources and classification can be different in space of generation and development. Following categories are common and useful for urban and rural areas. Table 1.5 Household Estimates (000's) Sr. No 1 2 3 4 5 6 7 8 Total

Cities Gujranwala Faisalabad Karachi Hyderabad Peshwar Bannu Quetta Sibbi

Household Size 7.3 7.0 7.0 7.0 7.0 6.7 7.0 6.7

1981 82 157 744 130 102 7 41 4 3,248

Number 1996 2006 241 493 338 561 1,503 2,402 248 381 236 343 12 18 143 286 9 15 4,726 6,505

2016 1,008 933 3,839 589 498 25 574 25 9,507

Source: EPMC (1996), Mahar et al. (2007), Iqbal et al. (2015)

1.7. 1) 2) 3) 4) 5) 6) 7) 8)

Sources of Generation in Urban Areas Residential, Domestic and Commercial areas. Institutions. Industrial Activities. Construction and demolition activities. Municipal Services. Agricultural Wastes. Treatment Plants. Special Categories

1.7.1. Residential, Domestic and Commercial Wastes This includes all organic and inorganic refuse from residential, domestic and commercial areas. The organic components of these wastes consist of materials such as food wastes, paper, cardboards, textile, plastic, rubber and leather and yard wastes. The inorganic components consist of items such as glass bottles, tin cans, aluminum, ferrous and non-ferrous metals, batteries, oil and paints etc. Commercial wastes are rich in paper, cardboard, plastic, glass, wood and other packing materials.

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1.7.2. Institutional Wastes This includes wastes from schools, colleges, government and private institutions etc. This category of wastes is like residential and commercial wastes but may also contains hazardous and non-hazardous wastes for example, chemicals from laboratories. The proportion of paper, cardboard and packing materials is generally much higher in this type of waste.

Solid Waste Urban

Semi-solid Waste Liquid Waste

Wastes

Solid Waste Rural Liquid Waste Muncipal Solid Waste Integrated Solid Waste Hazardous Waste Fig. 1.2 Types of Different Wastes

1.7.3. Industrial Wastes This waste is generated from various processes in small and large scale industries, classified as industrial wastes. These are highly heterogeneous in nature and are industry specific. Both hazardous and nonhazardous components are found in industrial wastes.

1.7.4. Construction and Demolition Wastes Construction and demolition waste are the wastes generated from construction, repairing, demolition and renovation of buildings and other structures. These include

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bricks, cement, stones, concrete, dirt, wood, plumbing and electrical parts, cement bags and plaster scrape etc.

1.7.5. Municipal Services Wastes These are the wastes produced by operations and maintenance of municipal facilities for example street sweepings. It also includes road site litter, tree trimmings, yard wastes from public parks, play grounds and dead animals etc.

1.7.6. Agricultural Wastes Wastes generated from all agricultural activities such as planting and harvesting of trees, animal farms, poultry farms and dairy farms etc. Wastes from dairy farms including feed lots, animal manure are also included in agricultural wastes.

1.7.7. Treatment Plant Wastes The treatment plant wastes include solid and semisolids in the form of sludge from water and wastewater treatment facilities. The characteristics of these types of waste depend upon the type of treatment plant.

1.7.8. Special Category Wastes All the wastes having special characteristics such as hospital wastes, slaughterhouse wastes, fly ash form thermal power stations radioactive wastes etc. These kinds of waste require special treatment and disposal techniques.

1.8.

Sources of Generation in Rural Areas

Details of the following are discussed in the upcoming chapters mentioned in front of each number. 1) Residential/Domestic wastes. (Chapter – 7) 2) Agricultural wastes (Plant/Crop wastes - Chapter – 4) 3) Animal wastes. (Chapter – 5) 4) Rural industrial wastes. (Chapter – 8)

1.9.

Waste generated through disposal in Urban and Rural Areas

Wastes generation is essential due to discarding of unwanted materials away for disposal. It is a continuous activity which is not very controllable. Huge quantities of municipal solid wastes are generated in all the mega cities of the world. The volume of municipal solid waste generated varies with the lifestyle of the people. It has been estimated that each American generates wastes about 4000 times his bodyweight;

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each West European 1000 times; and each citizen of the developing countries like Pakistan about 150 times. The United States alone generates more than 200 million tons of wastes a year-an amount "enough to fill a convoy of garbage-trucks stretching eight times around the globe". In Karachi, about 6000 tons of municipal solid waste (MSW) are generated every day. The average per capita generation of MSW in Pakistani cities is 0.4 - 0.6 kg per day. The quantities of wastes generated in some of the cities in Pakistan and comparison of wastes generation with other countries are shown Table 1.7 and Table 1.6, respectively. The population of the world is steadily increasing, but 90% of the yearly increase of world population is confined only to seven countries e.g. Pakistan, India, Bangladesh, Indonesia. China, Nigeria and Brazil. Pakistan's population is currently increasing by about 15 million per year. Lopsided planning has contributed to the rapid increase of population of megacities in developing countries. Population of mega cities like Karachi and Islamabad is increasing by half a million per year. By all accounts therefore the management of MSW will be a major challenge for years to come in all developing countries. Table 1.6 Quantities of Wastes in Different Countries Sr. No. 1 2 3 4 5 6

Country Pakistan India USA UK Singapore Japan

Quantity (kg per capita per day) 0.50 - 0.75 0.40 - 0.60 1.25 - 2.25 0.95 - 1.00 0.80 - 0.90 1.00 - 1.20

Source: CPCB (2000)

It is important to note there is a big difference in Pakistan between solid waste generation and the amounts reaching final disposal sites. In developed countries, the two figures are usually much the same since most waste arising must be disposed of formally (although there are moves towards the segregation of some components of waste at the source in several countries). In developing countries, including Pakistan, much more of the waste arising is recovered, mostly by scavengers, before it reaches the point of final disposal. For any figures related to the quantification of wastes to have any meaning they must be interpreted with the foregoing in mind. Also, estimating the amount of waste produced by households and then finally reaching at disposal systems, the statistics can be unreliable. The situation is made worse in Pakistan as there are no weighing facilities at most of the disposal sites and no tradition of waste sampling and analysis. However, the situation is changing and municipalities are realizing the importance of weighing and recently weighing facility has been installed at disposal sites are Lahore. Furthermore, the types and quantities of wastes arising and reclaimed vary with the locality and, to some extent, with the season; and areas with more traditional

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lifestyles tend to generate relatively small quantities of waste, and segregation and reclamation practices are more widespread. As the population grows and affluence increases the quantity of solid waste also is increasing. This is a logical relationship and is in accord with experience internationally. In any country, the amount of solid waste generated varies with the standard of living of its people. The composition of municipal waste depends on the affluence of the population contributing to the waste stream. It is essential to know the composition of waste, both at the source and at disposal, to assess the most suitable option for disposal and recovery. For example, the feasibility of composting is determined by a combination of the quantities of waste generated and the proportion of organic waste, amongst other factors. The quantity and organic content of solid waste are much less in rural areas where many waste materials are used traditionally and beneficially (e.g., for feeding animals, as soil conditioner, and as fuel).

1.10. Estimated waste generation in Pakistan The Ministry of Environment and Urban Affairs Division, Government of Pakistan, undertook a study during 1996 on “Data collection of national study on privatization of solid waste management in eight cities of Pakistan”. Table 1.7 Waste Generation Estimates Sr. No. Cities 1 2 3 4 5 6 7 8 Total

Generation (kg Rate capita-1 day-1) (kg ha-1 day-1) Gujranwala 0.469 3.424 Faisalabad 0.391 2.737 Karachi 0.613 4.291 Hyderabad 0.563 3.941 Peshawar 0.489 3.423 Bannu 0.439 2.941 Quetta 0.378 2.646 Sibi 0.283 1.896

Waste (t day-1) 824.0 924.3 6,450.0 975.7 809.3 36.0 378.0 17.0 10,414.3

Generated (t year-1) 300,760 337,370 2,354,250 356,131 295,395 13,140 137,970 6,205 3,601,221

Source: EPMC Estimates (1996), Mahar et al. (2007), Iqbal et al. (2015)

The study revealed that the rate of waste generation on average from all type of municipal controlled areas varies from 0.283 kg/capita/day to 0.613 kg/capita/day or from 1.896 kg/house/day to 4.29 kg/house/day in all the selected cities from Sibi to Karachi. It shows a particular trend of waste generation in which increase has been recorded in accordance with city's population besides its social and economic development. Table 1.7, presents the city wise waste generation rate with respective daily and annual estimate of solid waste.

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1.11. Composition of Municipal Solid Waste The composition of municipal solid wastes is the term that describes the distribution of each component of wastes by its percent weight of the total. The information is required for the selection of suitable treatment and disposal methods. For instance, MSW containing high percentage of biodegradable wastes e.g. food wastes and yard wastes are suitable for composting. Similarly, if recyclable materials like paper, plastic, cardboards, glass are presented in solid wastes, these materials should be recovered and recycled. The composition of MSW has been studied extensively. The precise composition depends upon the locality, season of the year, standard of living, land use etc. Important constituents of MSW generated in Pakistani cities are food wastes, paper, cardboard, plastics, rubber, textile, leather, yard wastes, wood, glass, tin, aluminum and other metals, and silt/dirt and construction and demolition wastes. Typical composition of MSW generated in Karachi and various cities are given in Table 1.8. Seasonal variations are often large in municipal solid wastes. Many fruit and vegetable wastes including bagus from sugarcane, mango peelings, and melon peelings are all seasonal. Huge volumes of these seasonal wastes alter the composition of MSW significantly. Composition of wastes also differs from locality to locality. People in a particular locality often have similar background in terms of incomes, tastes, and expenditure. Wastes from high income group localities is usually heavy in paper and packaging, while in low income group areas, the predominant constituent is usually food wastes. Construction and demolition wastes constitute a significant proportion of wastes in areas where these activities are in progress. Composition of wastes from commercial areas depends upon the nature of activities. Around offices and institutions usually paper and packaging are the major components while close to vegetable and fruits markets, food wastes are predominant. Similarly, wastes near dairy farms will be high in animal feed and manure while in the wastes from slaughter houses bones, blood and animal body parts will be commonly found. Efficient management of wastes requires an integrated wastes management plan. Techniques and technologies are available and the choice depends largely on the compositions of wastes. There is considerable content of plastic in the solid waste generated in Pakistan which is a cause of great concern. Plastic waste is released during all stages of production and post consumption every plastic product is a waste. Both the quantity and quality of plastic waste cause environmental problems. Quantitatively post consumption plastic waste is more important. This is so as they are found in large volumes and less weights. Most waste plastic recovered by the formal sector comes from industrial waste, which is less contaminated than the post-consumer stream. This waste is taken care of by the formal recycling sector. The much more heterogeneous domestic waste stream is left to the mercy of the informal sector. Some of the environmental issues of plastic waste are litter, emissions of hydrogen chlorides and dioxins from incinerators; and contamination from chemical additives. Plastic waste also presents a direct hazard to wildlife. Eliminating plastic bags improves the quality of compost and reduce the amount of waste requiring disposal.

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Table 1.8 Physical Composition of Waste (% weight) Item GWA FSD KRI HYD Plastic and 5.00 4.80 6.40 3.60 Rubber Metals 0.30 0.20 0.75 0.75 Paper 2.50 2.10 4.10 2.40 Card board 1.80 1.60 2.40 1.50 Rags 3.20 5.20 8.40 4.70 Glass 1.50 1.30 1.50 1.60 Bones 3.20 2.90 3.00 2.00 Food Waste 14.70 17.20 21.00 20.00 Animal Waste 1.00 0.80 3.00 5.80 Wood 0.80 0.70 2.25 2.25 Stones 5.70 4.60 3.50 3.00 Leaves, grass, etc. 12.80 15.60 14.00 13.50 Fines 47.50 43.00 29.70 38.90 Source: EPMC (1996), Mahar et al. (2007), Iqbal et al. (2015)

PWR 3.70

BNU 5.30

QTA 8.20

SBI 7.20

0.30 2.10 1.90 4.30 1.30 1.70 13.80 7.50 0.60 7.30 13.60 42.00

0.30 3.30 1.60 2.30 1.20 0.20 16.30 2.40 0.50 6.50 14.70 45.40

0.20 2.20 1.30 5.10 1.50 2.00 14.30 1.70 1.50 7.80 10.20 44.00

0.00 2.00 1.40 5.30 2.40 0.80 8.40 4.00 1.00 7.70 14.50 44.80

GWA= Gujranwala; FSD= Faisalabad; KRI= Karachi; HYD= Hyderabad; PWR= BNU= Bannu; QTA=Queta; SBI=Sibi

Peshawar;

Kraft bags decompose with the compost, whereas plastic bags don't break down and must be land filled. Currently, no technology exists that can screen out all plastic from the compost. The removal of the plastic bags from the composting program will dramatically reduce the operational costs associated with our composting operation The composition of waste has revealed that there is a considerable potential in solid waste management to make it a profitable enterprise. It may be realized that through sale of recyclable, composting, energy production and use of waste as earth filler; almost whole of the waste can be put into one of the above said uses. Only hazardous waste from hospitals and industries needs separate arrangements for its management. The typical composition of municipal solid waste in Pakistan is shown in Table 1.9. Table 1.9 Typical Composition of Solid Waste in Pakistani Cities (%) Composition Food waste Leaves, grass, straw, fodder Fines Recyclable

Percentage (%) 08.40 - 21.00 10.25 - 15.60 29.70 - 47.50 13.60 - 23.55

Source: EPMC (1996), Ali and Hasan (2001), Mahar et al. (2007), Iqbal et al. (2015)

1.12. Estimated waste collection in Pakistan In Pakistan, solid waste is mainly collected by municipalities and waste collection efficiencies range from zero percent in low-income rural areas to 90% in high-income areas of large cities. The proportion of waste collected is much less in many other areas of the country, particularly in poorer areas, where the only means of solid waste disposal is often informal scavenging by people and animals, natural biodegradation

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F.H. Khan

and dispersion, burning at the primary point of disposal, and local self-help for disposal to informal (technically illegal) dumping sites. The responsibility of municipal solid waste management rests basically with the municipality. In Pakistan, traditionally in big cities, the city district government, collect waste from households in middle to high-income areas and municipalities are in charge of street sweeping. Public waste collection is usually not efficient and mainly they do not have sufficient funds. Therefore, there is now a trend towards subcontracting a substantial part of waste collection and street sweeping services to private companies, which will be comparatively with higher efficiency. Subcontracting to private companies has so far not been fully practiced in Pakistan. Furthermore, there are a number of NGOs like “Waste Buster” that are active in waste collection and have done remarkable work. Collection rate of solid waste by respective municipalities ranges from 51% to 69% of the total waste generated within their jurisdiction. The uncollected waste, i.e. 31% to 49% remains on street or road corners, open spaces and vacant plots, polluting the environment on continuous basis. The rate and amount of the waste collected in all the selected cities are given in Table 1.10. Table 1.10 Waste Collection Estimates Sr. No.

Cities

1

Gujranwala

Collection Rate (%) 52.0

2

Faisalabad

54.0

499

149,737

3

Karachi

53.0

3,419

1,025,550

4

Hyderabad

51.0

498

149,282

5

Peshawar

61.0

494

148,102

6

Bannu

58.0

24

7,334

7

Quetta

50.0

189

56,700

8

Sibi

69.0

12

3,519

5,563

1,668,734

Total

Daily Collection (t/day) 428

Waste (t/300 days) 128,500

Source: EPMC (1996), Ali and Hasan (2001), Mahar et al. (2007), Iqbal et al. (2015)

1.13. Potential for waste recycling in Pakistan Under the present system, the municipalities are not carrying out any type of recycling activity. What happens normally is that the main recyclable items like paper, plastic, glass and metals are retained by the people themselves, which are later sold to street hawkers/waste dealers for recycling. Whereas the recyclable mixed with discarded waste are picked up by the scavengers who make 2 to 3 trips of different dumps and earn Rs. 80 to 150/day. As a whole, however, according to the estimates the amount of recyclable varies from 1,000 tons/years in Sibi to 513,743

1 Introduction

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tones/year in Karachi. The total income works out to be Rs. 5,056.5 million per year. Assuming a net expenditure on the collection, storage, separation etc. as 50%, the net incomes expected to be Rs. 2528.3 million per years. The city wise potential for waste recycling are given in Table 1.11. Table 1.11 Potential for Waste Recycling Sr. No.

Cities

1 2 3 4 5 6 7 8 Total

Gujranwala Faisalabad Karachi Hyderabad Peshawar Bannu Quetta Sibi

Recyclable ratio 17.20 18.10 26.55 16.55 15.30 14.20 20.50 19.60

Annual amount (Tons) 42,518 50,189 513,743 48,444 37,147 10,800 23,247 1,000 727,088

Gross Income Rs. (Million) 352.5 547.4 3,515.6 269.5 232.2 7.4 127.2 4.7 5,056.5

Net Income Rs. (Million) 176.7 273.7 1,767.8 134.7 116.1 3.7 63.6 2.4 2,528.3

Source: EPMC (1996), Ali and Hasan (2001), Mahar et al. (2007), Iqbal et al. (2015)

1.14. World Bank Funded Project Report During 2004, Pakistan Environmental Protection Agency (PEPA, 2005) conducted a study of solid waste generation in different cities of Pakistan which is follows (Table 1.12). From the Table 1.12, it is concluded that the present rate solid waste generation in Pakistan is 54,888 tons per day which is 20.034 million tons per year. The projected population for the year 2014 will be 197.77 m based on current annual growth rate of 2.61 % and as such the estimated projection for solid waste in 2014 will be 71,018 tons per day which will be 25.921 million tons per year.

1.15. Questions being asked Following are the question being asked from the Engineers and Scientist by the public sector. 1) What is rural waste? 2) What is the impact of rural waste generation at the farm? 3) What is the future in respect of rural waste generation? 4) What are the future challenges and opportunities to bring about the changes?

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5) How the various activities associated with rural waste generated at site that is storage, collection, transfer, transport, processing, recovery and disposal can be managed. 6) What does the term integrated solid waste means as applied to rural waste management? 7) What are day to day responsibilities of an operating agency in the rural area of Pakistan? 8) How farm/rural waste management and disposal system can be designed and implemented effectively. Therefore, answers to the above said questions need to be addressed carefully.

Table 1.12 Solid waste generation in 2004 City

Population (Million) 1998 Census

Population (Million) 2004

Urban Areas Karachi 9.269 10.818 Faisalabad 1.977 2.307 Hyderabad 1.151 1.343 Gujranwala 1.124 1.312 Peshawar 0.988 1.153 Quetta 0.560 0.654 Bannu 0.046 0.054 Sibi 0.082 0.095 Remaining 27.261 31.818 Urban Areas Rural Areas 88.121 102.853 Sub-Total 130.579 152.409 Add 3% for Hazardous Waste Grand Total

Solid Waste Generation Rate (kg per Capita per day)

Waste Generated (Tons per day)

Tons per year

0.613 0.391 0.563 0.469 0.489 0.378 0.439 0.283 0.453

663 902 756 615 564 247 24 27 14,414

2,420,680 329,230 275,940 224,475 205,860 90,155 8,760 9,855 5261,110

0.283

29,108 53,289 1,599 54,888

10,624,420 19,450,485 583,635 20,034,120

Source: PEPA (2005), Iqbal et al. (2015)

1.16. Farm/Rural Waste The farm waste includes agricultural, domestic and rural industrial wastes. Agricultural waste primarily originates from animals (excreta and byproducts of dead animals) and plants (leaves, stalks, stubbles and shells). Presently most of these wastes are either underutilized or unutilized. Methods of handling, treating and disposing of waste may adversely affect air, water and soil quality and may be of nuisance to those who dwell nearby. The nature, proportion and methods of utilization of wastes differ widely from place to place. Every farm with waste

1 Introduction

17

products requires a waste management system, and almost every farm is unique in its combinations of waste production, handling, storage, treatment and disposal either by recycling or by discharge. The domestic waste consisting of solid waste, silage and human excreta are very rarely disposed of properly in the rural area of Pakistan. Stagnant pools of water, carelessly handled garbage, free refuse littering the streets are some of the common features of rural Pakistan which is due to ill-conceived and traditionally insanitary habits of living and poor management of domestic wastes. Rural industrial wastes are not considerable and as such they do not pose any severe threat in disposal and management. However, if proper methods of disposal are followed then sanitary conditions can be maintained and some economic returns can also be gainfully made.

1.17. Three Step Model for Rural Waste Handling Presently domestic solid waste in Pakistan has not been carried out in a sufficient and proper manner in collection, transportation and disposal or dumping regardless of the size of the city: therefore, the environmental and sanitary conditions have become more serious year by year, and people are suffering from living such conditions. The scope of problems regarding solid waste management is very wide and involves the consideration of all the aspects relating to solid waste and its management, either directly or indirectly. These aspects may include rate of urbanization, pattern and density of urban areas, physical planning and control of development, physical composition of waste, density of waste, temperature and precipitation, scavenger's activity for recyclable separation, the capacity, adequacy and limitations of respective municipalities to manage the solid waste i.e. storage, collection, transportation and disposal.

1.18. Farm/Rural Waste Management Waste management can be defined as the discipline associated with the control of generation, storage, collection, transfer and transport, processing and disposal of wastes in a manner that is in accordance with best principles of public health, economics, engineering, conservation, aesthetic and other environmental considerations. Waste management includes all administrative, financial, legal, planning and engineering functions involved in the whole spectrum of solution to problems of waste caused thrust upon the community by its inhabitants. In the present days, the problems associated with rural waste management are complex because of the quantity and diverse nature of the wastes, funding limitation the impact of technology and the lake of social awareness amongst the rural community.

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1.19. Activities Associated with Farm Waste Management The activities associated rural waste management can be grouped into six functional elements. Details of the following activates are discussed in upcoming chapters of this book. (i) Waste Generation (ii) Storage (iii) Collection (iv) Transfer and Transport (v) Processing and Recovery (vi) Disposal

1.20. Farm Waste Management Solution A universal solution cannot be applied to waste management problems. Alternative waste management methods exist, creating a lead for economic analysis to determine the least cost solution. The least cost waste management method is a function of the type and volume of waste production and utilization, return and treatment cost. Different organizations in general, have tried to convert wastes into profitable products or less frequently into harmless disposable effluents. As this conversion has not always been possible, an assessment of the situation is desirable. Most collected wastes do not lend themselves easily or economically to utilization. The adoption of a new waste utilization process is a function of the extent to which it can improve the economic efficiency of the organizations associated with an improvement in costrevenue relationship.

1.21. Farm Waste Utilization In general, waste utilization has become an area which needs to be addressed very carefully. Waste utilizing products and usage of wastes are subject to the interacting forces of the market. Thus, wastes utilization is more than a matter of technical feasibility. The present system of organizing production does not yield the optimum degree of reuse. If utilization has a role in waste management scheme, then successful adoption of new technology will be the outcome of the market. Therefore, various efforts to find new usage for waste should include analysis of the economic feasibility of waste utilization process.

1 Introduction

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1.22. Terminologies used in Farm Waste Management and Disposal System Recycling Return of discarded material or article to the same product system, for example, the return of waste paper to make new paper. Recently, many broader definitions have been proposed, when applied to a forest tree may involve its use for re-creation, shelter, furnishing, paper and board, food and chemicals, heat and electricity. Refuse Solid organic waste in decomposing or non-decomposing state and excluding body wastes, for example, garbage, rubbish, ash, street washing, dead animals, solid market and industrial wastes. Garbage Decomposing organic waste resulting from the growing, handling, cooking or consumption of food products, decomposing animal waste; it is the most important component of refuse its byproducts are grace and fertilizer. Rubbish All non-decomposing wastes excluding ashes, paper, cans, card board, glass, wood, broken crockery and metal scraps easily scatter by wind or through careless handling. Ashes Waste products of coal and other fuels which may cause nuisance dust. Street Washings Waste materials from street surface, sidewalks, etc. Activated Sludge Sludge settled out of sewage previously agitated in the presence of abundant oxygen. Aeration Tank A tank in which the sludge, sewage or other liquid wastes is aerated. Biological Treatment Organic waste treatment in which bacterial and/or biochemical action is intensified under controlled conditions. BOD (Biological Oxygen Demand) It is an indirect measure of the concentration of biologically degradable material in organic wastes. It is the amount of free oxygen utilize by aerobic organism when allowed to attack the organic matter in an aerobically maintained environment at a specified temperature (20 oC) for a specific period (5 days).

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F.H. Khan

It is expressed in milligrams of oxygen utilized per liter of liquid waste volume (mg per liter) or in milligrams of oxygen per kilogram of solids percent. COD (Chemical Oxygen Demand) The amount of oxygen required for the chemical oxidation of organic matter in a liquid where the waste contain only readily available organic bacterial food and no toxic matter, the COD values can be correlated BOD values obtained from the same wastes. Contamination A general term signifying the introduction of microorganism into water, chemicals, organic or inorganic wastes, or sewage which renders the water unfit for its intended uses. Digestion Commonly refers to the anaerobic breakdown of organic matter in water solution or suspension into simpler or more biologically stable compounds or both. Pollution The presence in a body of water (or soil or air) of substances of such character and in such quantities that the natural quality of the body of water (or soil or air) is so degrades as to impair its usefulness or render it offensive to the senses of site, taste or smell. Contamination may accompany pollution. Settleable Solids Solids contained in sewage are waste matter that will separate by settling when the carrier liquid is held in a quiescent condition for a specified time interval. Putrefaction Putrefaction involves splitting of the complex organic compounds through the activity of micro-organism causing nuisance from odours, gases, etc. Kitchen wastes, offal and dead animals are example of perishable components of solid wastes. Sewage Used water or liquid waste of a community includes human wastes, household wastes together with street washings, industrial wastes, ground and strong water has may be mixed with it. Sanitation Prevention of sporadic outbreak of dangerous diseases by controlling or eliminating environmental factors contributing to the transmission of diseases. Aerobic Digestion In this, micro-organism obtain energy by endogenous or auto-oxidation of their cellular protoplasm. The biologically degradable constituents of cellular material are slowly oxidized to carbon dioxide, water and ammonia. In which the ammonia is further converted into nitrates during the process.

1 Introduction

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Anaerobic Digestion In anaerobic digestion, bio-degradable materials in primary and excess activated sludge are stabilized and oxidized to carbon dioxide, methane and other inert products. The primary digester serves mainly to reduce volatile solids while the secondary digester is mainly for solid-liquid separation, sludge thickening and storage. Composting The biochemical stabilization of solid wastes into a humus-like substance by producing and controlling an optimum environment for completing the process. C-N ratio (carbon to nitrogen ratio) The weight ratio of carbon to nitrogen in an organic system. Fermentation The process carried out by micro-organism that can partially decompose organic compounds into lower molecular weight of acids and/or alcohols. Pyrolysis The high temperature decomposition of complex molecules that occurs in the presence of an inert atmosphere (no oxygen present to support combustion). Calorific Value The amount of heat released from combustion of a unit weight of a substance. Incinerator Equipment in which solid, semi-solid, liquid or gaseous combustible waste are ignited and burned leaving solid residues containing little or no combustible material. Rendering Rendering refers to the extraction of fat from animal tissues by the action of heat which causes the cells to burst and the melted fat to run together in a form more or less convenient for collection. PV (Permanganate Value) It is normally used to produce a speedy estimate of oxygen demand of waste. It uses acidified permanganate solution to satisfy the oxygen demand over four hours at 27 o C and represents the amount of easily oxidized simple chemical matter. It is not meant to reflect the actual oxygen demand of living organisms. UOD (Ultimate Oxygen Demand) Used very infrequently. It measures the oxygen demand over a period of months at ambient temperature.

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F.H. Khan

SS (Suspended Solids) SS value is a measure of turbidity. Highly turbid waste looks very unpleasant but may appear much worse than their actual analysis. Percentage of Water The moisture content of a waste material is important to measure the characteristics of waste from the handling point of view. Absorption Field It is the name commonly given to the disposal field where the effluent from the septic tank is disposed of through sub-surface irrigation. Densification Densification is the process of increasing the material density with the result that a greater mass may occupy the same volume as the original material. Densification is a merely a process of compression of the matter removing the intra-particle voids etc.

References Alemayehu, E. (2004). Solid and Liquid Waste Management - for Health Extention Worker, Ethopia Public Health Training Initiative, The Carter Center, Jimma University and Ministry of Health and Education, Ethiopia. Ali, M., and A. Hassan. (2001). Integrating Recycling and Disposal System for Solid Waste Management in Karachi. Urban Resource Centre, Karachi. CPCB - Central Pollution Control Board (2000), Management of Municipal Solid Waste, Ministry of Environment and Forests, Parivesh Bhawan, East Arjun Nagar, New Delhi-110 032, India. EPMC (1996). Data collection of national study on privatization of solid waste management in eight cities of Pakistan. Engineering Planning and Management Consultant, Lahore, Pakistan. Iqbal, M., Breivik, K., Syed, J. H., Malik, R. N., Li, J., Zhang, G., and Jones, K.C. (2015). Emerging issue of e-waste in Pakistan: A review of status, research needs and data gaps. Environ. Pollut., 207, 308-318. Mahar, A., Malik, R. N., Qadir, A., Ahmed, T., Khan, Z., and Khan, M. A. (2007). Review and analysis of current solid waste management situation in urban areas of Pakistan. In: Proceedings of the International Conference on Sustainable Solid Waste Management, 5–7 September 2007, Chennai, India, pp. 34–41. PEPA (2005). Guideline for Solid Waste Management. Pakistan Environmental Protection Agency, Ministry of Environment, Government of Pakistan, Pakistan. Population Census of Pakistan (1998). Pakistan Bureau of Statistics, Statistics Division, Ministry of Finance and Economic Affairs, Islamabad, Government of Pakistan. World Population Review (2016), World Population Prospects - Global demographic estimates and projections by the United Nations, 340-S Lemon Ave Walnut, CA91789, United States.

Chapter 2

Necessity of Rural Waste Management and Disposal Systems Faizan ul Haq Khan*

Abstract Most of the population is living in the rural areas of Pakistan (80%). They are facing a lot of problems such as, site and area specific, rural waste management and disposal, sanitation, environmental pollution and health problems. Health is always given prime importance by all concerned with rural life. Open space is not a rural problem, rather this is a great blessing and always misused by the rural community. The rural community started throwing human excreta; cattle dung, refuse, domestic and all other wastes in the open space without considering its consequences in their future life. Latter on this great blessing (open space) becomes a source of various diseases in the rural areas due to miss management and disposal of rural waste, which disturb hygienic conditions of their normal life, results in outbreak of various diseases effecting their health. In this chapter, some of the benefits of proper disposal and best management techniques are discussed. Keywordss: Waste problems, rural health problems, rural sanitation, waste management, waste disposal, manurial values.

* Faizan ul Haq Khan Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. For correspondance: [email protected]

Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

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F.H. Khan

2.1.

Introduction

Ever since Adam threw the first apple core, wastes started accumulating on this planet. The word 'wastes' refers to useless, unused, unwanted or discarded material. The value of these waste material as a resource or as an object of further utility was seriously recognized after the oil embargo, due to limited availability of land particularly in cities and rising fuel prices. All over the world, wastes are now being looked as a "reserve, unused or partially exploited". Utilization of waste amounts to conserving rare and essential resources both energy and raw materials. Reasons for looking towards waste as a potential source are: waste is plentiful, it is free, it is flexible, its utilization is labour intensive and its recycling is approved. On a large extent, the producers as well as consumers create solid waste. The larger and more affluent the population, the greater the volume of wastes. The rate of increase of waste with the increase in population and standard of living is not well understood. It is however, a fact that the disposal problem in most of the countries is increasing dramatically not only because urban population is growing rapidly but also because the nature of goods and services are undergoing continuous change.

2.2.

Rural Health and Environment

Health is always kept on top priority by all the researchers and concerned such as doctors, engineers, social scientist and others. Town planner and environmental engineers are mainly concerned at the time of planning urban and rural areas. The villages have a lot of open space but villagers suffer from several diseases due to poor sanitary conditions, which is the biggest problem. The villagers need awareness and education on proper management and disposal of vegetative, animal, domestic and human waste, which are responsible for health problems and environmental pollution. These can be overcome by arranging public lectures, seminars, radio talks, telefilms, etc. related to best management and disposal techniques. Through above mentioned techniques they can get maximum benefits in their normal life.

2.3.

Problems of Health in Rural Areas

Health is always given prime importance by the town planners and environmental engineers. This is also applicable to village planning. In spite of open land scape the villagers suffer from several diseases due to poor sanitary conditions. Rural areas are characterized by stagnant pool, bad drainage; human excreta and cattle dung almost everywhere, refuse dumps, unprotected water supplies, etc. Generally, the approach of a village is welcomed by the mixed odor of decaying night soil and smoke from dry dung fuel, organic waste and wood. Therefore, sanitation is the real problem related to rural waste management. It is worth mention to indicate some other problems regarding rural waste disposal in true latter and sprite (Giuliano et al., 2009). (i)

Apart from poor housing and drainage system, mismanaged disposal of vegetative, animal, domestic and human waste adds another rural

2 Necessity of Rural Waste Management and Disposal Systems

25

problem leading toenvironmental pollution due to agricultural waste which is not eatable by animals and dumped in heaps for composting in very insanitary manner. (ii)

In most areas parasites, the digestive tract and hook warms are common. The rodents, flies, and other insects bread in the refuse while stray dogs, cattle, and chicken scatter the piled material far and wide. This, not only creates pollution problem also gives very poor quality manure.

(iii)

The animal dung and urine found on the roads and in the houses, if not disposed of properly that will provide breeding place for developing bacteria which causes different diseases.

(iv)

Storage of sundried dung cakes during rainy season in very insanitary manner, throwing domestic refuse out of house, which causes water stagnation, foul odor and breeding place for mosquitoes. Therefore, for ensuring better sanitary environment proper collection and transportation, safe and economical disposal of refuse is very important.

2.4.

Various Disease caused by Rural Waste

Human excreta is a source of infection. It is an important cause of environmental pollution and intestinal disease (WHO, 2013). The specific health hazards of improper excreta disposal are: (i)

Soil pollution - which results in contamination of the soil giving rise to diseases especially to those consuming vegetables grown on such soil.

(ii)

Water pollution - causes various intestinal and allied diseases. The decomposable organic matter and pathogenic contains in faeces are causes of many waterborne diseases as stated below: (a) Viral - Hepatitis, Poliomyelitis, (b) Bacterial - Cholera, Typhoid, Paratyphoid, Baci1liary dysentery, gastro- enteritis, Diarrhea, (c) Protozoal - Amoebiasis, Giardiasis, (d) Leptospiral - Well's disease, (e) Helminthic - Round worm, Whipworm, Threadworm, Hydatid disease, (f) Cyclops – Guinea worm disease, fish tap worm. (g) Small - Schistosomiasis.

(iii)

Contamination of food occurs through mice - organisms present in faeces which are a potential source of infection. The following are the

26

F.H. Khan

food-borne illnesses: (a) Bacterial - typhoid, paratyphoid, food poisoning, diarrhea, dysentery. (b) Viral - hepatitis, gastro-enteritis. (c) Parasites - Roundworm, Tapeworm, Hookworm, Hydatid disease, Whipworm etc. (iv)

Propagation of flies - flies are man's most dangerous enemy. The diseases transmitted through the housefly are, i.e. typhoid, diarrhoea, dysentery, cholera, gastro-enteritis, amoebiasis, conjunctivitis, trachoma, helminthic (worm) infestations.

Urination in the open areas produces nauseating odour and is also a source of health hazard as carriers of some diseases like B. Coli etc. It is not uncommon to see a bus stopping and passengers coming out for urination even in affluent localities. Very few toilet facilities exist and these are improperly designed, ill-maintained public toilets and urinals. These public facilities are far too inadequate in all big/small cities and villages of Pakistan. As such the solid wastes probably cause more damage than any other form of pollution. By providing better and workable facilities, and thereafter by enforcing pragmatic laws and educating public will considerably reduce the hazards of urban and rural wastes (Rydin et al., 2012).

2.5.

Problems of Rural Waste Management and Disposal System

From the days of primitive society, human and animals have used the resources of the earth to support life and to dispose of wastes on the earth itself. In early times, the disposal of human and other wastes did not pose a significant problem, because the population was generally small and scattered and the amount of land available for the assimilation of wastes was large. The capabilities of self-cleansing of the basic elements of natural ecosystem viz. air, water and land were not affected. Disposal and management of wastes can be traced from the time when human first began to congregate in tribes, villages and communities, and the accumulation of wastes became a health hazard to human life. The lack of any plan for the management of rural and urban wastes has led to the epidemic of plague and various other diseases. It was not until the nineteenth century that public health measures began on a systematic and large scale and received the consideration of public officials, who began to realize that food wastes had to be collected and disposed in a sanitary manner to control the vectors of disease. Urban and rural solid wastes are unavoidable in any society. Heaps of foul smelling garbage harbor flies, mosquitoes and stray animals. In some villages, rural waste is used for reclaiming stagnant ponds, marshes and similar patches of land. But this can also create unhygienic surroundings if not covered adequately by surface layers of

2 Necessity of Rural Waste Management and Disposal Systems

27

soil. Such open dumping cause severe air and ground pollution, in addition to making that area of land useless for any purpose till the wastes decompose.

2.6.

Benefits of Proper Disposal

Earlier people disposed of materials by burying or dumping waste in rivers and oceans. However, our society generates too many products which are difficult to recycle than discarding. Nowadays, economic considerations are the major criteria considered for waste utilization. Those are availability, value of chemical content, useful physical properties, collection and transportation, separation of waste material and environmental protection pressures, energy, quality of end product, employment of social attitudes. Therefore, the economic value of rural waste may be considered as energy generation, raw material for industries and manurial value.

2.6.1. Energy Generation Presently world population has been increasing at an alarming rate of 2-5%, energy consumptions have been increasing at a higher rate of 5-10%. High energy consumption reflects high quality of life which is associated with gross national product (GNP). Present energy needs are supplied almost by fossil fuels, which include coal, wood, petroleum and natural gas. The reserves of coal are approximately 90% of the estimated fossil fuel reserves. The remainder is divided equally between petroleum and natural gas with small reserves of tar-sand and shale oil (Batool et al., 2008). Petroleum and natural gas reserves are not sufficient. At present rate of fuel consumption, the petroleum and gas reserves will last in 125 and 250 years respectively (Fossil Fuel Overview, 2007). Generation of electrical energy by installing atomic power, thermal power and hydroelectric power involves huge capital investment. However, hydropower and nuclear power contribute to 33% and 2.4% of the total electricity supply, respectively, as shown in Table 2.1. Therefore, in this situation exploration of non-conventional sources of energy has become inevitable. Among renewable energy alternatives biomass is the best source of energy. Table 2.1 Historic Electricity Generation and Capacity Mix of Pakistan Entity Coal Oil Gas Hydro Nuclear

Electricity generation capacity (MW) 1980 2007 0.015 0.150 0.177 3.019 1.929 9.254 1.847 6.494 0.137 0.462

Source: Asif (2009)

Shares (%) 1980 2007 0.4 0.8 4.3 15.6 47.0 47.8 45.0 33.5 3.3 2.4

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F.H. Khan

About 80% of population in Pakistan is living in villages/rural areas. The main sources of energy in our villages are firewood, cattle dung, cakes, fermentable and non-fermentable agricultural wastes which are used because of its thermal efficiency as17.3%, 8.4%, 9.6% and 12% respectively (Asif, 2009). In Pakistani villages about 80% of total energy is supplied by firewood and cattle dung locally available. Nevertheless, the biomass available within the villages is sufficient to meet the immediate demand of the village if it is properly managed. Heat potential of some of the wastes can be significantly increased through modern technology and good management systems (Mahar et al., 2007). These wastes can be utilized to generate energy by anaerobic fermentation to get biogas the end products can be used efficiently. The other rural wastes such as night soil, poultry droppings dung and urine of various animals can also be used to produce biogas and fertilizer.

2.6.2. Raw Materials for Industries Several byproducts of crops which are either underutilized un-utilized can serve as raw material for various industries. These byproducts include straw, husk and bran of rice, straw of wheat, paddy, barley, mustered, pearl millet, shells of groundnut and castor, sugarcane bagasse etc. These materials are either composted or used as manure for disposal. Straw and husk of paddy, Straw of wheat and sugarcane bagasse are also used for various industrial purposes. The potential of other material is yet to be determined (Bagchi, 2004). Amongst animal’s wastes, the dried chicken manure is a suitable base for cosmetic face powder as equilibrium moisture content is not more than 12 to 15 %. Aggregate, comprising manure ground glass, fly ash etc., can be used for road laying are hard core. Manure can be used as a substance for fermentation by yeasts and recovery of alcohol may be possible. Dried chicken manure can be used as medicine for curing baldness. Recycling of faecal matter back to animals is gaining popularity due to its protein content. The by-product of dead bodies of animals are not properly utilized. At present, flaying is done to remove skin and hide for use in leather industries. In some cases, the bones are used as cattle feed after proper utilization and for preparing bone ash, bone charcoal, Dicalcium phosphate, etc. Excepting for skin and bones, other byproducts have little or no utility at present, even though there is vast scope for utilizing them.

2.6.3. Manurial Value Presently, Cattle dung and byproducts of various crops are mainly used for manure purpose. The NPK value of various animals and crop waste are in Table 2.2. The farm yard manure improves the soil fertility and soil structure. The byproduct of dead animals can be used as manure. Bones can be used as phosphate manure whereas, dried and powdered meat can be used as source of nitrogen manure which contains good percentage of nitrogen. The hairs which have no industrial value can also be converted into manure contains 8-9% nitrogen (Panda, 2011). Stomach garbage mainly consisting of undigested food, dung and other excretion can also be converted to manure (Khan et al., 1981).

2 Necessity of Rural Waste Management and Disposal Systems

29

Two wastes are completely utilized in rural areas of Pakistan. These are night soil and water weeds. Use of latrines in rural areas of Pakistan is rare. People go out to ease themselves in open fields, waste lands, road sides, banks of ponds and sides of railway tracks. The night soil left in open areas, either ferments, dries up or partly ferments and partly dries up. The dried material mixed with dust and produce airborne diseases in the local community. This also mixed with water resources of the villages. The wastes have very high manurial value and are very good source for increasing soil fertility (Khan et al., 2009). Therefore, rural areas of Pakistan have a tremendous wealth in terms of domestic refuse, under-utilized crop residues, animal excretion and their byproducts are known as waste. A systematic management and utilization approach applying modern innovations will not only in maintaining rural areas clean but will also provide sufficient energy, manure and raw material for many industries. Table 2.2 Approximate Manurial Value of Various Rural Wastes Materials Mustard straw Mustard stalk Castor shell Cotton stalk Isabgul Wheat straw Rice husk Paddy straw Pearl millet straw Sorghum stalk Sugarcane leaf Pigeon pea stalk Groundnut stalk Pea straw Oat straw Barley straw Fresh cattle dung Poultry dropping Cattle urine Horse urine Sheep urine Horse dung Sheep dropping Wood ash Ash gur furnace Rural street waste Domestic waste water

Nitrogen (%) 0.45 0.47 1.01 0.44 0.65 0.53 0.45 0.36 0.65 0.40 0.35 1.10 1.25 2.30 0.45 0.40 0.35 1.40 1.05 1.35 1.60 0.45 0.60 0.20 0.12 0.54 0.57

Phosphorus (%) 0.53 0.22 0.35 0.10 0.36 0.10 0.25 0.08 0.75 0.23 0.12 0.58 0.46 0.25 0.40 0.20 0.15 1.60 0.35 0.50 2.70 1.00 0.58 0.17

Source: Khan et al. (1981), Khan et al. (2009), Panda (2011)

Potash (%) 1.48 0.61 1.86 0.61 0.66 0.71 1.10 0.45 0.71 2.50 2.17 0.60 1.28 1.50 0.90 0.20 0.85 0.75 1.40 2.30 0.35 0.95 4.00 2.80 0.76 0.25

30

2.7.

F.H. Khan

Energy from Rural Waste Management

In the modem sense, nothing is waste, and much of the waste is being neglected although it could provide us with cheap energy. Rural wastes which are produced in large quantities every day all over the world consist of a variety of substances, but the major fraction is always organic in nature. At present, most rural waste is disposed of for no better use than so called sanitary land-fills. No doubt, there are other uses to which the rural waste can be consume. In Pakistan, big and small cities have large areas earmarked for waste dumping. Surprisingly, they are called sanitary land-fills, although they are highly insanitary in nature. These land-fills not only stink with highly obnoxious odour but are also infested with flies, rats, cockroaches and a variety of organisms which are potential health hazards. Positive aspect of the land-fills is that the decomposition process is always associated with release of gases, major portion of which is methane. Methane is the major component of all biogas and has high fuel value. Microbes trapped in the buried waste gradually breakdown the organic matter to produce free methane. Slow release of the gas makes tapping of this resource to be used as fuel, which is difficult and costly. Still, at many places, this energy is being tapped and used for various purposes including generation of electricity. Addition of water to the land-fills will accelerate the process of bio-degradation and associated gas production. It is estimated that gas produced by each cubic meter of land-fill may provide energy equivalent to around Rs. 1,000 (approximately). In the United States, there is a hotel complex which is running on energy released from land-fill. Even smaller cities, towns and villages can go for this source of energy, detail discussion is given in Chapter-5. Therefore, smaller towns and villages will be in advantageous positions. Wastes produced in these areas have higher percentage of organic matter which will produce more gas per unit volume of the waste which would certainly make the process more attractive (Upadhyay et al. 2014).

References Asif, M. (2009). Sustainable energy options for Pakistan. Renew. Sustain. Ener. Rev., 13, 903-909. Bagchi, A. (2004). Design of Landfills and Integrated Solid Waste Management. 3rd Edition. John Wiley and Sons. Inc., Hoboken, New Jersey, USA. Batool, S.A., Chaudhry, N. and Majeed, K. (2008). Economic potential of recycling business in Lahore, Pakistan. Waste Manage., 28, 294-298. Fossil Fuel Overview (2007). Living with the oceans. – A report on the state of the world's oceans, World Ocean Review, maribus gGmbH, Pickhuben, 2-20457 Hamburg, Germany. Giuliano, P., and Ruiz-Arranz, M. (2009). Remittances, financial development and growth. J. Dev. Econ., 90: 144-152.

2 Necessity of Rural Waste Management and Disposal Systems

31

Khan, A. A., Azhar, F. M., Khan, I. A., Riaz, A. H., and Athar, M. (2009). Genetic basis of variation for lint color, yield, and quality in cotton (Gossypium hirsutum L.). Plant Biosys., 143, S17-S24. Khan, A., Aziz, A., Gilani, A., and Khan, A. (1981). Effect of different levels of nitrogenous and phosphatic fertilizers and pickings on fibre and yarn strength in cotton related to cellulose, protein and other characters. Pak. J. Agri. Res. 2, 1320. Mahar, A., Malik, R. N., Qadir, A., Ahmed, T., Khan, Z., and Khan, M. A. (2007). Review and analysis of current solid waste management situation in urban areas of Pakistan, Islamabad, Pakistan Panda, H. (2011). Manufacture of Biofertilizer and Organic Farming, Asia Pacific Business Press, 106-E, Kamla Nagar, Dehli-110 007, India. Rydin, Y., Bleahu, A., Davies, M., Dávila, J. D., Friel, S., De Grandis, G and Lai, K. M. (2012). Shaping cities for health: complexity and the planning of urban environments in the 21st century. Lancet, 379, 2079. Upadhyay, S., and Sharma, M. P. (2014). A review on configurations, control and sizing methodologies of hybrid energy systems. Renew. Sustain. Ener. Rev., 38, 47-63. WHO (2013), World Health Staistics, World Health Organization, WHO/CCO/13.01/ Pakistan.

Chapter 3

Rural Waste Characterization Faizan ul Haq Khan and Abdul Nasir Awan*

Abstract Waste generation in the rural areas are heterogeneous in nature with different composition and variability in their general behavior and properties such as, physical, chemical and biological properties. In this chapter, possible Information related to the characteristics and all those parameters are provided which determines the best use of rural waste. For the best management and disposal techniques, author has tried to provide a concrete knowledge about density, compaction characteristics, heating value and so on. This will enhance understanding and knowledge about the proper use of raw material received from rural waste in agricultural based industries and as organic matter/manure in the agricultural lands of the rural areas. This will also be very helpful in designing and executing projects related to rural waste in harvesting the actual benefits from rural wastes. Keywords: Characteristics of rural waste, waste composition, manurial values of waste, Pyrolysis of refuse, Compaction characteristics.

3.1.

Introduction

Characteristics of rural waste need to be addressed for the development of feasible waste management systems. These are important to decide the considerations of reuse of waste, liquids, transport of raw products, recovery of specific waste components, irrigation, byproduct development, energy and fertilizer value etc.

*

Faizan ul Haq Khan˧ and Abdul Nasir Awan Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

34

F.H. Khan and A.N. Awan

Similar reuse possibilities exist with solid wastes, such as raw material for industries, energy source, animal feed and as a soil conditioner. Rural waste is heterogeneous mass available form crop, raising animal, human habitation and rural industries. The proper design of treatment and disposal systems will depend upon the quantity, physical and chemical characteristics of the waste. The design of waste management system must provide for more operating flexibility and reserve capacity, better controls for environment pollution and cheaper environmental processing equipment. However, characterization of the average composition and properties of wastes provide the starting point for design. Therefore, forecasting for likely changes in waste characteristics should be considered in the design (Guerrero et al., 2013).

3.2.

General Composition, Physical and Chemical Parameter of Waste

General composition, Physical and chemical parameters for characterization of rural waste are given below.

3.2.1. General Composition for Characterization of Farm/Rural Waste 3.2.1.1. - Plant Waste •

Stalk

•

Straw

•

Pod shell

•

Leaves

•

Flowers,

•

Spikelet etc.

3.2.1.2. - Animal Waste •

Dung / droppings

•

Urine

•

Carcass

•

Spoiled fodder

3.2.1.3. Domestic Waste •

Human excreta

•

House sweepings and kitchen waste

•

Sludge

3.2.1.4. Rural Industrial Waste •

Ash

3 Rural Waste Characterization •

Broken earthenware

•

Tannery effluent

•

Leather trimmings

•

Rice husk and bran

•

Bagasse

•

Wood chips and sawdust

•

Cotton rags etc.

35

3.2.2. Physical Parameters for Characterization of Farm/Rural Waste 3.2.2.1. Total Wastes •

Size

•

Shape

•

Volume

•

Weight

•

Density

•

Density stratification

•

Surface area

•

Compaction

•

Comp actability

•

Temperature

•

Colour

•

Odour

•

Physical taste o Total solids o Liquid o Gas

3.2.2.2. - Solid Wastes •

Soluble (%)

•

Suspendable (%)

•

Combustible (%)

•

Volatile (%)

•

Ash (%) o Soluble (%) o Suspendable (%)

•

Hardness

36

F.H. Khan and A.N. Awan

3.2.2.3. Particle Characteristics •

Size distribution

•

Shape

•

Surface

•

Porosity

•

Sorption

•

Density

•

Aggregation

3.2.2.4. Liquid Waste •

Turbidity

•

Colour

•

Odour

•

Taste

•

Temperature

•

Viscosity data o Specific gravity o Stratification

3.2.2.5. Total Solids (%) •

Soluble (%)

•

Suspended (%)

•

Settleable (%)

•

Dissolved oxygen

•

Vapour pressure

•

Effect of shear rate

•

Gel formation

3.2.2.6. Gaseous Waste •

Temperature

•

Pressure

•

Volume

•

Density

•

Particulate (%)

•

Liquid

3 Rural Waste Characterization

37

3.2.3. Chemical Parameters for Characterization of Farm/Rural Waste 3.2.3.1. General •

pH

•

Alkalinity

•

Hardness (CaCO3)

•

BOD (biological oxygen demand)

•

COD (chemical oxygen demand)

•

Rate of availability of nitrogen

•

Rate of availability of phosphorus

•

Crude fiber

•

Organic (%)

3.2.3.2. Combustion Parameter •

Heat content

•

Oxygen requirement

•

Flame temperature

•

Combustion product (including ash)

•

Flash point

•

Ash-fusion characterization

•

Pyrolysis characterization

•

Toxicity

•

Corrosivity

•

Explosivity

•

Biological stability

•

Attractiveness to vermin

3.2.3.3. Inorganic and Elemental •

Moisture content

•

Carbon

•

Hydrogen (P2O5 and phosphate)

38

F.H. Khan and A.N. Awan

Table 3.1 Composition of Farm/Rural Waste Human faces without urine Approximate Quantity: Approximate composition Moisture content Organic matter content (dry basis) Nitrogen Phosphorus (as P2O5) Potassium (as K2O) Carbon Calcium (as CaO) C/N ratio Human urine Approximate quantity Approximate composition Moisture content Organic matter content (dry basis) Nitrogen Phosphorus (as P2O5) Potassium (as K2O) Carbon Calcium (as CaO)

135-270 g per capita per day moist/wet weight basis 35-70 g per capita per day dry weight basis Percentage 66 - 80% 88 - 97% 5.0 - 7.0% 3.0 - 5.4% 1.0 - 2.5% 40 - 55% 4 - 5% 05 - 10% Volume: 1.0-1.3 liters per capita per day Dry solids: 50-70 g per capita per day Percentage 93 - 96% 65 - 85% 15 - 19% 2.5 - 5% 3.0 - 4.5% 11 - 17% 4.5 - 6%

Source: Gajalakshmi et al. (2008)

Table 3.2 Chemical Composition of Fresh Manure from Various Animals based on Dry Litter-free Material Chemical constituents

* Sheep manure (%)

Ether soluble substances 2.8 Hot water soluble organic 5.7 matter 18.5 18.7 Hemicellulose Cellulose 20.7 Lignin 25.5 Total protein 17.2 Ash * Solid and liquid excreta, **Solid excreta only Source: Gajalakshmi et al. (2008), ASAE (2005)

** Horse manure (%)

* Cow manure (%)

1.9 2.4 23.5 27.5 14.2 6.8 9.1

2.8 5.3 18.6 25.2 20.2 14.9 13.0

3 Rural Waste Characterization

39

Table 3.3 Chemical Nature of Different Types of Manure Manure

Moisture (%)

Nitrogen (%)

80 75 68 82 52 56

1.67 2.90 3.75 3.75 5.68 6.27

Cattle Horse Sheep Pig Pigeon Hen

Source: Gajalakshmi et al. (2008), ASAE (2005)

3.2.3.4. Organic •

Soluble (%)

•

Protein nitrogen

•

Phosphorus

•

Lipids

•

Starches

•

Sugars

•

Hemicellulose

•

Lignins

•

Phenols

•

Benzene oil

•

ASB (alkyl benzene sulphonate)

•

CCS (carbon chloroform extract)

•

PCS (polychlorinated biphenyls)

•

PNH (polynuclear hydrocarbons)

•

Vitamins

•

Insecticides

•

Sulphur contents

•

Toxic materials

•

Eutrophic materials o Nitrogen o Potassium o Phosphorus

Composition of dry matter P2O5 (%) K2O (%) 1.11 0.56 1.25 1.38 1.87 1.25 3.13 2.50 5.74 3.23 5.92 3.27

40

F.H. Khan and A.N. Awan

General composition of farm/rural waste is given in Table 3.1. Chemical composition of fresh manure from various animals based on dry litter-free material is given in Table 3.2. Chemical nature of different types of manure is given in Table 3.3.

3.3.

Refuse (Garbage, Rubbish and Other Litter)

The quantities of garbage, organic rubbish and dead vegetation available on farms and in villages are extremely variable. The constituents of refuse also vary from place to place depending upon the economic status and eating habits (Loehr, 2012). In Pakistan, mostly garbage and food wastes are fed to animals and hence the amount of garbage is limited to very small quantities of non-edible vegetable products rich in cellulose. There is also little waste-paper, rag etc., in the refuse. Ash, particularly in cold climate, street sweeping and trash constitute a major portion of the waste. In warm areas with a high rain fall, most of the waste vegetation finds its way into the refuse. However, in many villages the amount of such refuse is insufficient to provide even a satisfactory compostable mass when mixed with the night soil.

3.4.

Bulk Density

Bulk density is defined as the weight if unit volume of a material. It is expressed in grams per cubic centimeter. In waste handling, the bulk density is normally given in the condition (as received) or stored. The presence or balance of water can of course alter the value. The bulk density of most solids wastes is considerably lower than the ultimate density of their components (EPMC, 1996). The low initial density and poor compaction characteristics (at moderate pressure) of solid wastes which limit carrying capacity and thus contribute the high cast of collection and transportation.

3.5.

Compaction Characteristics

Compaction is frequently required to reduce volume and to increase the density of refuse to reduce transportation costs and the disposal space required for final deposit. For combustion and gasification and densification of biomass provides particular particle size density and pile porosity required by a given combustion process (Hoornweg and Bhada-Tata, 2012). The final density depends on the ram pressure employed in the press and on the characteristic of the solid. One of the factors affecting compaction characteristics is the moisture content of refuse (PEPA, 2005).

3.5.1. Viscosity Viscosity is a measure of the fluid’s resistance to shear when the fluid is in motion. The viscosity of liquid decrease with temperature of liquid or semiliquid wastes. One should consider the minimum temperature at which the material can be readily pumped.

3 Rural Waste Characterization

41

3.5.2. Acidity pH measurement should be made for liquid or semisolid waste. This information is valuable because acidic or basic waste require special attention in handling, storage and incineration. A knowledge of pH helps in avoiding the selection of materials which might react in storage and during handling thus cause rusting, corrosion and other effects.

3.5.3. Heating Value The heating value is expressed in kilo calories per kilogram of the material (as received) dry and moist without ash. The calorific value of the material is needed to calculate heat release, burning rate, viscosity, and amount of supplementary fuel required and other details of incinerator design. Frequently mixing and blending of waste is required to obtain a more uniform feed. In case of plant and animal wastes, the final disposal for energy purposes is based on calorific value.

3.5.4. Moisture The moisture content of solid is defined as that weight of material lost after 24 hours at 104oC to 110oC. For liquids or semi solids a different measurement apparatus and procedure is recommended. This involves distilling the sample with a volatile solvent, usually toluene and benzene for measuring water in the trap. The moisture measurements are very important in rural waste disposal because the moisture content of the material affects the burning capacity, composting ratio and various industrial processes.

3.5.5. Volatile Matter The volatile matter is that portion that is driven off in gas or vapour form when the material is subjected to a standardized temperature test. The determination of volatile matter is valuable in disposal of rural waste for energy purposes. The ASTM procedure for its measurement involves heating a specified quantity of material in a weighed platinum crucible in a furnace chamber at 950oC ± 20oC for 7 minutes. The material is heated in absence of air to prevent oxidation.

3.5.6. Ash Ash is the residue after combustion of the material. Ash is always reported on moisture free basis. The weight of ash is important as it is to be handled after the combustion of various crop residues and is to be used for the application in the agricultural land as soil conditioner. An elemental analysis of ash is important to decide its value for agricultural lands and to study the water pollution problem if it is mixed with water.

3.5.7. Fixed Carbon The fixed carbon is the combustible residue which remains after driving off the volatile matter. The fixed carbon content is calculated as fallows,

42

F.H. Khan and A.N. Awan

Equation 3.1 % =

−

%+

%+

%

3.5.8. Refuse Pyrolysis Pyrolysis is the change brought by the action of heat in the absence of air. Pyrolysis of most organic materials results in: (i) (ii) (iii)

a solid residue composed of ash and carbon, a condensable liquid product, water plus mixed organics, and, a gas

These products might be used for recycle as a source of organic raw material or used as a fuel. The first step in refuse pyrolysis is to prepare quantitative flow diagram with material and energy balance (USDA-NRCS, 1996; Pirsaheb et al., 2013). Given below is an example of flow diagram indicating refuse pyrolysis. (Figure 3.1)

Fig.3.1 Material Flow of Refuse Pyrolysis Source: NRCS -USDA (2000), Smith and David (2008)

References ASAE (2005). Manure Production and Characteristics - ASABE Standards (American Society of Agricultural Engineers), CEIRC (CAUL Electronic Information Resources Consortium), Council of Australia, Australia. EPMC. (1996). National study on privatization of Solid Waste Management in eigth cities of Pakistan. Engineering Planning and Management Consultant, Lahore, Pakistan. Gajalakshmi, S., and Abbasi, S. A. (2008). Solid waste management by composting: state of the art. Crit. Rev. Environ. Sci. Technol., 38, 311-400. Guerrero, L. A., Maas, G., and Hogland, W. (2013). Solid waste management challenges for cities in developing countries. Waste Manage., 33, 220-232.

3 Rural Waste Characterization

43

Hoornweg, D., and Bhada-Tata, P. (2012). What a waste: a global review of solid waste management. Urban Dev. Ser. Knowledge Papers, 15, 1-98. Loehr, R. (2012). Agricultural Waste Management: Problems, Processes, and Approaches. Academic Press, New York, USA. NRCS-USDA. (2000) Agricultural Waste Management Field Handbook, Natural Resources Conservation Service, United States Department of Agriculture. United States of America. PEPA. (2005). Guideline for Solid Waste Management. Pakistan Environmental Protection Agency, Ministry of Environment, Government of Pakistan, Pakistan. Pirsaheb, M., Khosravi, T., and Sharafi, K. (2013). Domestic scale vermicomposting for solid waste management. Int. J. Recycl. Organic Waste Agric., 2, 1-5. Smith and David G. (2008) Apparatus and process for converting biomass feed materials into reusable carbonaceous and hydrocarbon products. U.S. Patent Application No. 12/210, United States of America.

Chapter 4

Plant Waste Generated in Rural Areas Faizan ul Haq Khan, Abdul Nasir Awan and Shafique Anwar*

Abstract Plants waste generated in the rural areas are significant in scientific manner for economic and environment point of view. The nature and quantity of plant waste vary from crop to crop. The plant waste can be used for burning as fuel having different calorific values. This can be used as fodder or feed for animals and can also be converted into manure. The plant waste can be used in different industries for manufacturing papers, card boards, win boards and chip boards which are used for various purposes. The plant waste can very successfully be used as building material during construction in Pakistan. The calorific value of plants is also known as energy value, which is on an average equal to 4800 kcalkg-1 on dry weight basis. The plant waste can be converted into fuel such as, pellets, brickets and balls, through manual operation, animal operations and mechanical operations. Some other techniques can also be used to convert plant waste into fuel such as gasifiers. Different methods are used to convert plant waste into manure which can be used as soil conditioner to enhance the fertility level of soil. Keywords: Plant waste, organic waste, building material, energy value, compost, pelletizer, waste grinder, gasifier.

*

Faizan ul Haq Khan˧, Abdul Nasir Awan and Shafique Anwar Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

46

4.1.

F.H. Khan, A.N. Awan and S. Anwar

Introduction

Plant waste primarily originate from the roots, stems, leaves, shells or pods of field crops or products of utilized and under- utilized commercially uncultivated plants. Considerable waste may be available from the fruit and plantation crops also. The nature and quantity of plant waste available vary from crop to crop and variety to variety. The estimated quantity of residues available from various crops is presented in Table 4.1. The woody portion of the plants is generally used for burning and nonwoody portion is used for animal feed or is converted into manure by traditional method of heaping. It is not a waste material but it underutilizes constitutes of major waste. The proper management and disposal of plant residues may not be helpful in maintaining proper sanitary conditions but may dividends to the farmers. The commercially non-cultivated plant which are unutilized or under-utilized, yield variety of useful products like fiber, floss, gum, resin, rubber, tan, dye, oil drug and lac. However, the description of commercially non-cultivated plants and their byproducts, and crop residue used for fodder is not considered as waste.

4.2.

Disposal of Plant Waste

In the present technological and fast changing situation, it is desirable that the disposal of plant waste is done in scientific manner from economic and pollution considerations. Table 4.1 Approximate Quantity of Residue Available from Various Crops Crop Residue Mustard stalk and straw Castor stalk Castor shell Wheat straw Sesame straw Cotton stalk (green) Paddy straw Rice husk Sugarcane bagasse Sugarcane trash Maize cobs Groundnut shell Brinjal straw Cumin straw Banana pseudostem Jute sticks Potato haulm Pigeon pea stalk Gram straw Pearl millet straw Source: Jilani (2007)

Quantity (kg ha-1) 2000 to 2500 1800 to 2200 500 to 700 2000 to 2500 1900 to 2000 4000 to 5000 2500 to 2600 250 to 260 20,500 9,500 1000 to 1500 1000 to 1200 1,450 to 1500 1200 to 1250 9000 to 9500 1500 to 2000 500 to 600 1500 to 2000 1000 to 1200 400 to 500

4 Plant Waste Generated in Rural Areas

47

The fore-most economic consideration for the farmer is to sell the waste material at high prices to the industries. It is only possible when the plant waste has potentially to be used as raw material for some useful product (Jilani, 2007). Technology for the utilization of byproduct of some crops like paddy has been developed at exploitable level. Similar systems need to be developed for other crop byproducts. Figure 4.1 shows the various utilities of paddy and its byproducts.

Fig. 4.1 Paddy Crop Utilization System Source: Kumari and Grover (2007)

4.3.

Industrial Utilization of Plant Waste

4.3.1. Pulp and Paper As most of the crop residues have cellulose as major constituent, their preferable utilization may be in paper and pulp industries. Paddy, wheat straw and sugarcane bagasse are three important raw materials for this industry. Other crop residues need to be explored for paper making through systematic research and development programme. The cellulose material with low lignin content is desired raw material for pulp production (Conway and Ross, 1980; Gupta et al., 2009). The properties of various crop residues in relation to pulp and paper making are given below in Table 4.2. Depending upon the properties, crop residues may be used for the preparation of different types of papers like fine paper, blotting paper, filter paper packing and file board, straw board, greeting card, album paper and cover paper. The details of the industrial use of rice husk and bran will be given latter.

48

F.H. Khan, A.N. Awan and S. Anwar

Table 4.2 Properties of Crop Residues Crop residue Sugarcane bagasse Rice husk Paddy straw Groundnut shell Corn shell Corn cob Cotton stalk Wheat straw Banana stem Fire wood

Cellulose (%) 53.70 34.80 49.80 32.00 26.60 36.50 45.70 54.40 46.70 51.50

Pentons (%) 23.80 16.17 28.40 11.20 27.70 28.10 18.50 28.20 15.90 10.60

Lignin (%) 20.00 24.50 16.00 20.70 29.40 10.40 26.00 16.70 18.10 31.30

Ash (%) 1.65 12.90 16.00 6.30 0.10 1.48 0.80 6.60 8.96 0.82

Source: Gupta et al. (2009)

4.3.2. Building Material Some of the waste material like paddy straw, cotton stalk and wheat straw are used for constructing kachha houses by villagers. The husk amounting to 20 – 25 % of the total rice milled may be used for production of cementing material/binder. The detail will be discussed latter. Sugarcane bagasse, rice straw, wheat straw and jute sticks are used for the preparation of roofing sheet which may be used by the poor people. Even advanced countries like USA are showing interest in the production of paper houses for low income group. Manufacturing of paper roofing sheets mainly involves the process like pulping, board making, corrugation and drying, impregnation, fire retardant treatment and finishing. Some other industrial utility of various agricultural waste are given in Table 4.3, Table 4.3 Industrial Value of Various Agro-wastes Waste material Corn cob

Utilization Furfural, sugarcane and solvents, plastics oxalic acid, Acetic acid and foam.

Bagasse

Furfural

Rice husk

Plastic, furfural, structural bricks, cement, oxalic acid.

Rice straw

Furfural, cellulose fibers.

Cotton stalks

Furfural, plastic foam, resins and binder.

Groundnut shell

Vanillin, building board, adhesive extender, activated charcoal.

Source: Gupta et al. (2009)

4.3.3. Energy Value In general, the crop wastes have an average energy content of 4800 kcal kg-1) on dry weight basis. The presence of moisture reduces the energy content proportionality.

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The energy stored in plant material may be released by drying the plant material and burning it directly or it may be converted to liquid or gaseous fuels through a series of process shown in Figure 4.2, given below indicating conversion systems suitable for plant wastes.

Fig. 4.2 Biomass Conversion System Source: Brown et al. (2011)

4.3.4. Direct Burning Direct burning is an exothermic process which converts the stored chemical energy in the fuel to heat energy. In Pakistan, agricultural wastes like cotton sticks, groundnut shells, sugarcane bagasse, corn cobs and straw of various crops are burnt directly for fuel purposes. The thermal efficiency of these wastes used in domestic chulhas (fire burning places/wood burning stoves) is less than 10 %. The efficiency of utilization can be increased significantly by briquetting the material by compaction. The compacts or briquettes could be easily handled, stored and burnt on grates, boilers and domestic level more effectively (Huber et al., 2006; Li et al. 2015). The efficiency of heat utilization can be increased by burning the agricultural waste like rice husk, groundnut shell and paddy straw in cyclone furnace. The results of the experiments conducted at the rice process engineering center showed the highest furnace efficiency up to 80 % if the system is properly designed.

4.3.5. Densification of Plant Waste Densification is a process of compression of matter removing the intra-particle voids. Densification helps not only in direct burning of plant residues but also in gasification. The reason for densification of biomass for combustion and gasification is as given below: (i)

Densification provides the particle size, density and pile porosity

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F.H. Khan, A.N. Awan and S. Anwar

required by a given combustion process. (ii)

Densification facilitates bulk storage, handling, conveying, and automatic feeding.

Densification process includes bailing, briquetting, pelleting, tableting and roll compaction. Solid waste has relatively high cellulosic fraction which when properly processed makes it suitable for use in the solid fuel fired furnace. The first step of densification is the size reduction by a hammer-mill shredder. The material is reduced in size, but not into a uniform size distribution. After size reduction, the solid waste material is passed through an air classifier system and the heavy fraction is removed. The light material flies and subsequently is screened, where most of the fine material (grit, glass etc.) are removed. The screened light fraction is then palletized.

4.4.

Agro-waste Compaction Machines

Agro-waste machines are of three types, e.g. manually operated, bullock operated and power operated. Manually operated compaction machine is suitable for individuals and families in rural or village areas who can gather waste agricultural material scattered in the villages or rural areas, converted the same into briquettes and use them as domestic fuel. The machine works on the principles of a reciprocating engine. The capacity of this machine is to prepare 50 kg of briquettes fuel per day (8 working hours). Bullock-operated machine can be operated with the help of a single bullock and it has a capacity to prepare 150 to 200 kg of briquettes fuel per day (8 working hours). The power operated compaction machine can be operated by 3 horse power (H.P.) electric motor through a derive system.

4.5.

Pyrolysis

The term ‘pyrolysis’ refers to the transformation of a complex molecule (like cellulose) into and other simpler molecules in an inert (non-oxidative) environment through the action of heat. Within the field of fuel conversion pyrolysis is often used synonymously with incomplete combustion. Most organic substances are thermally unstable. When heating in an oxygen-free atmosphere, they can be split through a combination of thermal cracking and condensation reaction into gaseous, liquid and solid fractions (Qu et al., 2004). In contrast to the combustion process, this is highly exothermic, whereas pyrolytic process is highly endothermic. For this reason, the term destructive distillation is often used as an alternative term for pyrolysis. The characteristics of the three major component fractions resulting from the pyrolysis are; (i)

A gas stream containing primarily of hydrogen, methane, carbon monoxide, carbon dioxide and various other gases, depending on the

4 Plant Waste Generated in Rural Areas

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organic characteristic of the material being pyrolyzed. (ii)

A fraction that consists of a tar and/or oil stream that is liquid at room temperature and contains chemicals such as acetic acid, acetone and methanol.

(iii)

A char consisting of almost pure carbon plus any inert material that may have entered the process.

The pyrolysis system produces a clean fuel that can substitute fossil fuel. It converts the heterogeneous wastes into a more desirable homogeneous form. The char has a fuel value and can be used as land fill, soil conditioner or filter medium. The liquids have fuel values and may also have chemical value. The gas has a relatively low heating value compared to natural gas. This is not economical to transport it over great distance and is difficult to store. It contains a significant amount of carbon monoxide and requires special safety precautions in handling. Although pyrolytic process needs careful attention. Briquetting or pelletizing the agro based improves the efficiency of neutralization, but the smoke may still create new sense. When the biomass is subjected to carbonization (pyrolysis) or charring under controlled conditions and then the char briquette with or without binder, the heating values may be comparable to those of coke/coal available for domestic purposes. The process outline, range of yield, heating value, heat recovery and overall burning efficiency are shown in Figure 4.3. The importance of paru for energy and food production through irrigation is given in Figure 4.4.

Fig. 4.3 Process Outline for Paru Fuel, from Renewable Biomass Wastes Source: McKendry (2002a), Menon et al. (2012)

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Fig. 4.4 Importance of Paru Fuel for Energy and Food Production Cycle (Schematic Plan) Source: McKendry (2002b), Menon et al. (2012)

The charring can be carried out in an empty oil drum on a small scale. About 15 - 25 kg of biomass can be charred in about 8 hours. This charred material can be extruded by a hand extruder or pelletized manually after mixing with any available binder. The cost of production is negligible expect for the manual labour. A cupola type, community level charging unit with a capacity of 1 to 3 tons per batch and meant for rural areas has been designed. The unit can be built as a permanent structure with ordinary bricks having in side lining of fire bricks to conserve heat. Several fixed trays with respective charging doors are provided to feed biomass and to remove charred material. The heat of pyrolysis is supplied by the combustion of biomass in the furnace provided in the unit. For two times of biomass, charring unit, about 400 kg of biomass is needed to provide the heat of pyrolysis. The main advantage of the system is that no electric power is consumed. The operation is simple and can be handled by unskilled labour. The continuous mechanized plant of three tons per day capacity consist of a shredder, pyrolyzer with heating and cooling arrangements a binder for mixing the binder, continuous extruder and a dryer. Considering the cost of collection of raw materials, it is desirable that the plant of requisite capacity should be located near the source of availability of raw materials. The paru fuel has the following advantages over direct burning of biomass: Smokeless burning, faster cooking, sustained combustion, easy to burn, lower ignition temperature compared to coke or coal, better heating value than coal, convenient to gasify, easy to handle and store, overall lower consumption of feed biomass and pellets can be made in any size and shape depending upon the use.

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4.6.

53

Equipment used for Pyrolytic Coal Production

Different equipments are used in the pyrolytic process for coal manufacturing from plant and domestic waste. Waste collector is manually operated simple pull type rake used to collect plant waste for pyrolytic coal production (Figure 4.5). The rake may be made of mild steel or bamboo. A person can collect one quintal of dried leaves in one hour if the leaves are spread all over the land. Waste cleaner is a simple and cheap manually operated equipment which can separate combustible material like paper, leaves, peels of fruit, vegetable residues and cloth cutting from domestic waste (Figure 4.6).

Fig. 4.5 Rake Type Waste Collector

Fig. 4.6 Waste Cleaner (Manually Operated)

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4.6.1. Waste Grinder Grinding of waste is an operation to increase the density of plant waste and decrease the volume of waste material to be transported. The grinder can reduce the size of plant waste to less than 25 mm right at collection site (Figure 4.7). Thus a 100 kg of gunny bag can store about 20 kg of plant waste instead of 3.5 to 5 kg if it is unground. The weight of the machine used is not more than 15 kg and having a capacity of one quintal per hour.

4.6.2. Waste Pyrolyzer The waste pyrolyzer is made of ordinary metal drum with a holding capacity of 10 kg of dried plant/domestic waste (Figure 4.8). The waste material filled in this drum is ignited from bottom layer holes while other holes are closed with lids. Fire moves up due to chimney kept over the drum. When the fire reaches the second layer of holes, holes of first layer are closed and holes of second layer are opened. In this way fire moves up from second to third layer while fire is extinguished below holes of second layer for want of oxygen. Thereby, the waste is converted into pyrolytic coal powder. The pyrolyzer is very cheap.

Fig. 4.7 Hand Operated Waste Grinder

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Fig. 4.8 Pyrolyzer

4.6.3. Coal Pelleting Machine Coal pelleting machine as shown in Figure 4.9, is hand operated worm-type machine. It compacts the lose material like pyrolytic coal powder into cylindrical compact pellets of 25 mm diameter and 75 to 100 mm length. The capacity of the machine is 20 kg per hour. Fig. 4.9 Manually Operated Pelleting Machine

Power operated pelleting machine as shown in Figure 4.10 can be operated by 5 HP electric motor and can produce one quintal pellets of 25 mm diameter and 75 to 100 mm length in one hour. The calorific value of pyrolytic powder is 4500 kcal kg-1 and if coal powder is mixed with clay then its calorific value will be 4000 kcal kg-1.

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Fig. 4.10 Waste Pelleting Machine, Worm Type, 5 HP Electric Motor Operated

4.7.

Gasification

Gasification is the process of treating biomass so that only gas is produced. The biomass is successfully heated up, dried and pyroylzsed to produce gases and char. The aim of gasification is to transfer the combustion value of the solid fuel to gaseous energy, preferably to chemical energy (Basu, 2013). The charcoal resulting from pyrolysis is converted into gas by partial combustion with oxygen or steam. Shown in Equation 4.1. 1 + "# → " 2

%# " → "

%#

Equation 4.1 – Gasification of Charcoal The composition of the product gas is determined by the biomass feed stock and gasification agent used, and the conditions such as pressure, temperature, residence time, heat loss and external heat input. Advantages of gaseous fuel over solid fuel are; •

It is easy to clean, transport and combust.

•

It causes little pollution.

•

It can be burnt in an internal combustion engine.

Gasification produces several types of gases. These can be roughly divided into three categories, according to their heat of combustion per unit volume (vol) at ambient conditions as shown in Table 4.4.

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Table 4.4 Typical Composition of Dry Clean Product Gases (vol %) CO

H2

CO2

CH4

CnHn

H2

Low Joule Value (LJV) 17.0 gas Medium Joule Value 61.0 (MJV) gas High Joule Value (HJV) gas

18.3

14.2

1.8

-

48.7

Joule Value MJm-3 4.75

28.0

2.0

8.0

-

1.0

13.61

-

0.9

81.2

3.4

14.5

31.65

Source: Basu (2013)

The gasification processes to produce various types of gases were basically developed for coal and peat. However, biomass contains much more oxygen and hydrogen than coal which reduces the amount of steam necessary to effect gasification. Furthermore, its sulphur content is usually low. On the other hand, as produced biomass often contains large amount of water, after drying it will attract an equilibrium amount of water if not properly stored. Apart from causing energy losses in drying, this adds to the complexity of the process. The biomass is often in an inconvenient shape and unless the gasifier is specifically adopted, extensive feed preparation such as grinding and pelleting may be required.

4.8.

Gasifiers

The gasifier consists of two components, e.g. a producer gas and an air-blower for circulating air through the reactor as shown in Figure 4.11.

Fig. 4.11 Gasifier System Source: Basu (2013), Vera et al. (2013)

The hot producer gas can directly be used for various thermal applications in industry after incorporating appropriate safety devices, or may be used for substituting diesel fuel in an already existing diesel engine after cleaning and cooling it. The complete gasifier-engine system consists of four major components such as producer gas reactor, gas cleaner and cooler the mixture and engine Figure 4.12.

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Fig. 4.12 Gasifier-Engine System Source: Vera et al. (2013)

The producer gas reactor produces the gas by partial combustion of biomass which is hot and dirty with tar, vapours, soot, particles, etc. To make the gas engine worthy, it is cooled to near ambient conditions and cleaned to remove particulates. The proper pre-processing of the gas required for long and unimpaired life of the engine is done by cooler cleaner assembly. Cooling is effected by use of water scrubbing. When a continuous supply of cooling water is not available, air cooling is done along with removal of tar by condensation and removal soot and ash by centrifugal techniques. Air and clean gas are mixed together in a proper proportion in a mixture before they enter the engine. The drive require for the movement of the gas through the entire flow circuit is obtain from engine itself and so a separate blower is not needed. The gasifier may be classified into four categories such as; (i)

Updraft gasifier

(ii)

Downdraft gasifier,

(iii)

Fluidized-bed gasifier,

(iv)

Suspended fuel gasifier

4.8.1. Updraft Gasifiers Updraft gasifier as shown in Figure 4.13, incorporates the simplest method in which oxygen/air contacts a bed of char on a grate producing CO/CO2 at high temperatures. This hot gas rises through the hot char, converting the char to CO and H2. At the next level, the hot gases pyrolyze the incoming biomass, and finally, at the top of bed the gases dry the biomass. The counter flow heat exchange produces low temperature exit gas. This gas is loaded with tars, oils and water which can cause problem in combustion. The resulting gas must be burnt directly because the tars are difficult to remove. Updraft gasifiers are especially appropriate for oil-fired boilers.

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Fig. 4.13 Schematic Diagram of Updraft Gasifier Source: Vera et al. (2013), Basu (2013)

4.8.2. Downdraft Gasifiers In downdraft gasifier as shown in Figure 4.14, air or oxygen is injected above the char mass, causing pyrolysis of the incoming biomass and producing char and oils. These oils then pass over the hot char and are cracked to gases, thus very little oil is produced. For this reason, downdraft gasifiers are particularly suitable for running internal combustion engine.

4.8.3. Fluidized Bed Gasifiers Fluidized-bed gasifier as shown Figure 4.15, have advantages of having a high heat transfer rate is due to very high circulation rate and processing of wide range of biomass sizes. However, they are not as efficient as downdraft gasifiers in consuming char or cracking oils and tars due to short contact time. There is also a tendency for the light biomass fraction and lighter char fraction to separate from the bed prematurely. However, the technology of fluidized-bed gasification is not well developed.

4.8.4. Suspended Fuel Gasifiers Suspended fuel gasifier as shown in Figure 4.16, offers high throughputs and the processing of small particles as potential advantages. The technology of suspension gasification needs to be addressed carefully and a lot of research and development work has to be done to reach at practicable stage.

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Fig. 4.14 Schematic Diagram of Downdraft Gasifier Source: Vera et al. (2013)

Fig. 4.15 Fluidized Bed Gasifier Source: Vera et al. (2013), Basu (2013)

Therefore, problems in small-scale on farm gasification of crop residues are; (i)

Most of the crop residue do not flow well resulting in choked reactors.

(ii)

Most crop residue have a density of 100 kg m-3 or less. This requires densification of the residues and a large holding capacity of the reactor or frequent /continuous feeding of the reactor.

(iii)

Substantial quantities of tar are produced during the gasification of crop residues. The gas mixture cannot be used as an engine fuel without separation of the tars.

(iv)

Most of the crop residues have high percentage of ash with relatively low fusion temperature resulting in slag formation at normal

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operating temperature. The slag chokes the reactor. Therefore, the selection of crop residues with favorable characteristics is a critical step in development of a successful small size gasifier.

Fig. 4.16 Suspended Fuel Gasifier Source: Vera et al. (2013), Basu (2013)

4.9.

Liquefaction

The liquid fuels offer an advantage over gaseous fuels that they can be easily stored and transported. The biomass can be liquefied by first converting it to synthesis gas then to liquid fuel. It may be directly liquefied bypassing the gaseous intermediate phase.

4.9.1. Indirect Liquefaction The conversion of biomass derived synthesis gas to liquid fuels encompasses several catalytic processes and technologies. The production of liquid fuel from biomass requires integration of three essential processing areas: (i)

Generation of synthesis gas (H2 + CO),

(ii)

Synthesis gas modification, and

(iii)

Liquid fuel synthesis and product refining.

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The synthesis gas modification involves particulate removal, acid gas removal, adjustment of H2/CO ratio via the water shift reaction and separation of the hydrocarbon fraction from the synthesis gas. Table 4.5 compares the relative status of major liquid fuel synthesis technologies and their potential for being adopted to biomass feed stocks. Table 4.5 Alternative Liquid Fuel Production from Biomass Derived Synthesis Gas Fuel type

Fuel use

Technology status

Methanol

Straight motor fuel and blend with gasoline Motor fuel

Commercial

Gasoline Fisher-tropsch liquids

Fuel oil gasoline

Higher alcohols

Straight motor fuel and blend with gasoline Major chemical feed stock, gasoline processors

Olefins

Commercial (from methanol) Commercial Experimental Process in demonstration

Potential production from biomass High High Low, Process too complex, not suitable for small scale High, Needs further development High but process is noncompetitive economically (yet)

Source: McKendry (2002a), Basu (2013)

The liquid fuel synthesis technologies may be divided into three major areas: (i) (ii) (iii)

Catalytic combination of the hydrogen and carbon monoxide from gasified biomass to produce methanol and methyl fuels; Further conversation of the biomass based on methanol into gasoline; Direct conversation of olefin rich gases from biomass pyrolysis into gasoline.

Simplified block diagrams of above three conceptual biomass-to-liquid fuels technologies are shown on Figure 4.17.

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Fig. 4.17 Simplified Block Diagram of Alternative Biomass-to-liquid Fuel Process Source: McKendry (2002a), Basu (2013), Vera et al. )2013)

The following reaction is used to make methanol from synthesis gas. (Equation 4.2)

"

%# → %& "%

Equation 4.2 – Methanol Production The synthesis gas is compressed to 50 - 500 atmospheric pressure (atm) and passes over a chromium or copper oxide catalyst at 250 - 350oC.

4.9.2. Direct Liquefaction Attempts have been made to apply methods developed for liquefaction of biomass. In this process, 30% by weight biomass is slurried with anthracene oil and heated to 370oC under high pressure (160 atm). This process is plagued with the problems because the oil does not allow high concentration of wood to be injected into the reactor. An aqueous pretreatment has permitted higher concentration of more reactive wood to be used in the reactor. Oil can be produced relatively low oxygen content. Problems in commercialization of production of liquids fuels from biomass: (i)

Thermochemical production of liquid fuels from biomass using existing technology requires a relatively high capital investment cost compare with fermentation of ethanol.

(ii)

Attainment of economics of scale in facilities for liquid fuel production from biomass is inhibited by the lack of concentrated biomass resources.

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(iii)

Liquid fuel production from coal and shale appears to be more attractive economically than using biomass because economy of scale.

4.10. Hydrolysis The hydrolysis of cellulose to produce fermentable sugars holds much promise to augment world supplies of ethanol and food. Ethanol is produced by fermentation of vegetable sugars. About 1.5 kg of sugar yields one liter of ethanol. Molasses (30% and more of sugar) can also be used as base material for ethanol production. It has been estimated that if half of the molasses. Concentrated acid (HCl, H2SO4, H3PO4) readily depolymerizes and solubilize cellulose at ambient temperature to produce a mixture of sugars and oligomeric sugar. This mixture, when subjected to dilute acid at evaluated temperature, yields almost stoichiometric quantities of sugar. The major problem associated with concentrated acid processes is economically separating and recovering the corrosive acid from sugar. In the dilute acid processes, the cellulose is hydrolyzed using dilute acid (generally 0.5 to 1%) at elevated temperature. The major problem associated with this process is that the acid at elevated temperature also catalyzes the degradation of sugar to byproducts. Without recycle dilute acid processes are limited to a nominal 55% conversion of cellulose to hexose. With recycle (or the equivalent of multiple hydrolysis stages) the conversion of cellulose to hexose can be obtained more than 80%. At elevated temperature, the dilute acids cellulose is also extremely corrosive. Enzymatic processes use celluloses to hydrolyze cellulose to hexose. The celluloses are produced by several microbes. The enzymatic processes operate under mild conditions and there is no degradation of the sugar produced. The major disadvantages are the high cost of the enzyme utilized per unit production of glucose and the necessity of energy intensive and costly pretreatments to obtain high yields. Ethanol is most suited for spark ignition engines, though it can be used in compression ignition engine by certain engine modification (Brown et al., 2011). In petrol engines, ethanol can be used in two ways: (i) (ii)

In dual fuel operation, a gasoline (ethanol 20%, petrol 80%) with engine modifications. With 100% ethanol with following modifications: (a) By increasing compression ratio; (b) Changing of ignition timing to avoid pre-ignition; (c) Enlarging carburetor jets; (d) Preheating air inlet; (e) Heating of manifold and raising coolant water temperature; (f) Adding 0.25% by volume of anti-corrosive additives; (g) Colder spark plugs;

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(h) Using stainless-steel for fuel tank and other fuel pipes; (iii)

Cold start device with small quantity of gasoline from separate small tank operated by the manifold vacuum.

Simple sugar plant material (biomass) can be converted into ethanol by yeast fermentation. The ethanol has high energy content compatible with the internal combustion engine. Mechanical expression of the juice in roller mills from sugarcane and by diffusion from beet, results in a feed containing 13 to 16% fermentable sugars. On a smaller scale, starch crops may be dry milled to release the starch grains and produce slurry which is then heated with a thermophilic bacterial amylase at 90 oC for thinning followed by saccharification (hydrolysis of the dextrin to glucose) by a gluco-amylose at 50 oC to 60 oC. Fiber may be removed either before or after saccharification. Ethanol is produced by yeasts under anaerobic conditions according to the Equation 4.3: ' %(# "' →

2

# %) "%

2 "#

Equation 4.3 – Ethanol Production On a glucose conversion basis, the alcohol weight yield is around 50%, but since a proportion of the sugar supplied is used foe cell growth and maintenance energy, or is converted to other metabolism, the actual yield is usually about 87% to 90% of the theoretical, giving a weight yield around 45% on feed. However, the proportion of energy recovered in ethanol is over 90%. The regulation of the ethanol production is complex. The concentrations of substrate, oxygen and product (ethanol) all affect yeast metabolism and cell viability then practicable. The level of fermentable solids generally used is 16 to 25% giving final alcohols concentrations of 7 to 12%. The ethanol is separated from the fermentation brew by distillation. An efficient distill will produce to a 96% ethanol/water mixture. Production of anhydrous alcohols requires a further distillation following addition of a suitable entrainer. The treatment of distillery slops probably represents the most serious problem in large-scale production. Stillage has a BOD of between 20,000 and 40,000 and a pit of about 4.5, but the exact composition depends on the substrate being used for fermentation (Gaeta-Bernardi, 2016). With yeast-recycling techniques many the yeast solids is removed and will not appear in the stillage effluent. Stillage may be treated by land disposal, irrigation, evaporation for animal feed, evaporation for incineration, activated sludge treatment, lagooning and anaerobic digestion.

4.11. Anaerobic Fermentation Anaerobic treatment or digestion is generated by bacteria which operate in the total absence of oxygen. These bacteria feed on complex organic molecule which they digest to obtain energy and structural building unit for their own single-celled bodies. The digestion process is a two-stage reaction with liquefaction and a gasification phase. Liquefaction is the process of breakdown of large organics such as carbohydrate, proteins and fats into smaller molecules such as simple organic acids

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and alcohols (Saharan et al., 2011). Gasification usually occurs simultaneously, converting the simple acids to methane and carbon dioxide. If plant waste is subjected to anaerobic treatment, methane and carbon dioxide gases are produced. The gas obtained through anaerobic fermentation of any organic material is known as biogas. The methane being a combustible gas may be used as a source of energy. However, the biogas available per unit weight of various plant wastes in given in Table 4.6. Table 4.6 Quantity of Biogas available from Various Plant Wastes Waste material Rice husk Sun-hemp waste Leaves and stalk of sunflower Pearl-millet husk Mustard straw Fresh grass

Quantity of biogas (L kg-1) 615.0 360.0 300.0 250.0 190.0 630.0

Content of methane (%) 59.0 58.0 55 – 65 55 – 65 70.0

Source: (Saharan et al., 2011)

4.12. Manurial Value Organic waste used as a low-degrade fertilizer or soil conditioner has a decidedly real benefit to most soils but particularly to heavy clays or loose sand in which its use can be increase crops several folds. For the application of plant wastes as manure, the organic solid waste is subjected to bacterial decomposition. The end product available is called as humus. The entire process involving both the separation and bacterial conversion of the organic solid waste is known as composting. Composting offers an opportunity to recover and reuse a portion of nutrients and organic fraction in solid waste. The major objectives of composting are to stabilize putrescible organic matter, to conserve the crop nutrients and organic matter as much as possible and to produce a uniform relatively dry product suitable for use as a soil conditioner and garden supplement or for land disposal. In general, the chemical and physical characteristics of humus vary according to the nature of the starting material, the conditions under which the composting operation was carried out and extent of decomposition (Panda, 2011). Some of the properties of the resulting humus that distinguish it from other natural materials are: a dark brown to black colour, a low carbon-nitrogen ratio, a continually changing nature due to the activities of the microorganism, and a high capacity for base exchange and for waste absorption.

4.13. Classification of Compost System Compost system may be classified on the general basis:

4 Plant Waste Generated in Rural Areas (i)

Oxygen usage

(ii)

Temperature

(iii)

Technological approach enclosed

67

Aerobic or Anaerobic Mesophilic and Thermophilic Open or windrow and mechanical or

Aerobic composting takes place in the biological system in which oxygen is present, while anaerobic system is free from oxygen. Aerobic composting generally is characterized high temperature, absence of foul odours and is more rapid than anaerobic composting. Anaerobic composing is characterized by low temperature, production of odours intermediate (reduced) products and generally proceeds at a slower rate than does aerobic composting (Panda, 2011). The main advantage in anaerobic composting is that the process can be carried out with a minimum of attention and as such it can be sealed from the environment. The Mesophilic composting requires intermediate temperature (15 to 25oC) which is most cases is the ambient temperature. Thermophilic composting is conducted at 45 to 65oC. In practice, most processes include the two ranges. Compost systems falling under the category of ‘open’ or ‘windrow’ are those in which the entire process is carried out in open. The material is usually stacked in elongated windrows. In mechanical system, on the other hand, the greater part of initial composting activity takes place in an enclosed unit, the digester. Most of the mechanical processes involve windrowing towards the end of the process to allow the composting material to mature.

4.14. Factors Affecting Composting Rate Environmental factors, like moisture, temperature, pH level (hydrogen ion concentration), nutrient concentration and availability, and oxygen concentration control the rate of composting process as they influence the biological activity (Insam, 2013; Panda, 2011).

4.14.1. Moisture content Water concentration in the compositing pile plays a very important role in decomposition rate. This is related to the role of water in microbiological life activities, as well as to the factor that the water is essential for many other reactions that occur in the pile. Large quantity of heat is generated during decomposition and unless sufficient water is present in the pile, it will tend to dry out and the decomposition rate will drop to almost zero. The theoretical moisture content in composting is 100%. However, the practical moisture content is a function of aeration capacity of the process equipped and of the structural nature of the material being composted. The maximum permissible moisture content varies from 75 to 85% for the most of the fibrous vegetative waste (straw, dry grasses, dry leaves) and from 50 to 60% for the waste of green vegetation like vegetable trimmings and wet garbage. The moisture content of the waste can be

68

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raised by adding an absorbent if the maximum permissible moisture content for a given waste is excessively low. Thus, if straw is added to vegetable trimmings, the maximum permissible moisture rises in proportion to the amount of straw added. The addition of an absorbent is also needed if the moisture content of the waste in its ‘raw’ state is excessively high. The maximum moisture content at which bacterial activity takes place is from 12 to15%. Obviously, the closer the moisture content of the composting mas approaches these low values, the slower will be the compost process. As a rule-of-thumb, the moisture content of composting mass should not drop below 45 or 50%.

4.14.2. Temperature Temperature is a key environmental factor affecting biological activity. The temperature range at which life is generally divided into three sub-ranges cryophilic (5 to about 10oC), mesophilic (10 to 40oC) and the thermophilic (45 to 70oC). Modern composting processes are designed to operate within the Mesophilic and Thermophilic ranges. The range of optimum temperature for the composting process is quite broad, i.e. from about 35oC to about 55oC, because of the many groups of organism taking part in the process. Unless a closely controlled digester is used, a uniform temperature does not prevail throughout the mass of composting material at any one time expect at the start of the process when material is at ambient temperature. When temperature is lower than 35oC the efficiency and the speed of the process increase with increase in temperature. It begins to diminish as the temperature exceeds 30oC and approaches 35oC. The slope of the curve showing efficiency or speed of the process as a function of the temperature would be practically a plateau between 35oC and 55oC. As the temperature exceeds 55oC, efficiency and speed begin to drop abruptly. Then become negligible at temperatures more than 70oC.

4.14.3. Hydrogen-ion (pH) level The optimum pH range for most bacteria is between 6 and 7.5, and for fungi between 5.5 and 8.0. The pH drop from about 6.5 to 5.5 in early stages of mesophilic digestion and then rises rapidly during the thermophilic stages to slightly more than 8.0 and diminish to 7.5 during cooling and maturing stage. In a practical operation, little can be done to alter the pH level prevailing in the pile due to economics and the need for nitrogen conservation. If lime is used to increase the pH in the early stages, its effect is to raise the pH beyond a desirable level and drive off the nitrogen in the form of ammonia.

4.14.4. Aeration Aeration of the compost pile is necessary to provide oxygen to support aerobic microorganism, to carry away heat generated in the pile by biological action and to remove moisture from the pile. The supply of oxygen to the pile is usually provided by natural aeration through the porous mass of material. Periodic turning of the pile assists in

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aeration and tends to enhance thermophilic activity and maintain uniform moisture content and temperature distribution throughout. It is believed that efficient aeration is achieved by turning composting windrow pile once a day or once every several days. For reasonably fine material (2.5 cm or less), oxygen penetrate a windrow pile to a depth of 15 to 20 cm. It is calculated that when the material is composting at a peak rate, the oxygen within the pore space in the material is used up in less than 20 minutes. The oxygen consumption rate depends not only on temperature but also on the fitness of grind material, its moisture content, its composition, the population of microorganism and degree of agitation.

4.14.5. Carbon/Nitrogen Ratio The micro-organisms which decompose residues require nitrogen for their growth and activities. The amount of nitrogen require per unit of organic matter varies with the type of the organism involve in the process. Molds for example, which incidentally are extremely active in the process, require 1 part nitrogen for every 30 parts carbon. Micro-organism use carbon as and energy source and nitrogen for cell building, thus the process of decomposition involves the reduction of the relative proportion of these elements, known as C/N ration from an original level which may range from 20:1 to 70:1, to a point where the available carbon has been consumed and activities cease. The final C/N ration usually lies between 15:1 to 20:1 but may be higher if the initial ration was near the top of the range. The initial C/N ratio is the deciding factor in the speed at which decomposition takes place. The ideal initial ratio is between 30:1 and 35:1. One should not attempt to compost materials such as saw dust, corncobs, paper and the like because the carbon-nitrogen ratio is well over 100 and the lack of nitrogen becomes the controlling factor in the biological process of digestion. These high carbon-nitrogen ratio materials are already stable and do not need composting.

4.15. Technologies for Composting Methods The development of composting started about a century ago. Some of the methods and processes developed till now have been mentioned as under (Fuchs and Cuijpers, 2016).

4.15.1. Indore Method It was evolved for composting animal manure to a depth of about 1.5 meter either on flat ground or in pits. At later stages, it involved stacking on open ground of alternate layer of readily putrefiable materials like night soil, animal manure, sewage, sludge and garbage, and stable organic matter such as straw, leaves and municipal refuse.

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The composting period was about six months, during which time the material was turned twice and so it was likely as for a great part of the time the decomposition in the center of the stack was anaerobic (Misra et al., 2016). The length of the period allowed for decomposition was probably advised in view of the health dangers of composting human sewage. The liquor from the decomposing mass was recirculated.

4.15.2. Beccari Process Beccari process is a mechanized and enclosed process widely used in East European cities. In this, the material is piled up in enclosed cells for an initial period of anaerobic decomposition, and then air vents are opened so that the final stages of decay are partially aerobic. Material is loaded in enclosed cells on the top; unloading door is provided in front. Air vents, when opened, create partially aerobic condition.

4.15.3. Verdier Process It is an improvement over Beccari process. In this, provision is made for the recirculation of gases or of drainage liquors possibly creating more aeration.

4.15.4. Bordas Process In this process, the silo cell is divided by a grate. When the material is partially digested, it drops into the lower chamber. This is apparently an improvement on Beccari process where air is forced through a central pipe and along the walls, eliminating anaerobic condition.

4.15.5. Earp-Thomas Process A silo type multigrate digester is used for producing compost by a continuous aerobic process using rotary ploughs, air is used for aeration.

4.15.6. Frazer Process In this process a fully mechanical aerobic digester with shredded organic material is used. The material is continuously agitated as it moves downward and brought in contact with the gases of decomposition. This is a salient feature of the process. The composted material is screened as it leaves the bottom of the digester and the tailings are recycled.

4.15.7. Dano bio-stabilizer (Dhano process) It is a long rotary steel drum or cylinder set at a slope of about 5o from the horizontal. Refuse with or without sewage sludge is added to the digester. As the digester rotates, the wastes are moved slowly forward. Water can be added to the digester to increase the moisture content of refuse. Aeration is achieved by means of two rows of air jets fixed along the length of the cylinder. The CO2 and used air escape through vents. The cylinder is of large capacity (20 tons per day). Agitation is achieved by turning

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the cylinder at the speed of 1.5 to 5 revolutions per minute (rpm). Retention time in the cylinder is from 3 to 5 days. The compost is drawn from the cylinder into vibratory or rotary screen with 1 cm opening. The tailings are hand-picked and large undigested organic material separated by separator. The glass pipes are separated by a gravity separator. The energy required is 12–16 kwh per tons of refuse. The screened compost is piled or windrowed for maturing for 6-10 days.

4.15.8. Vam Process The domestic refuse is carried by locomotives to sidings where it is tipped from wagons into composting cells constructed on both sides of the rails. The refuse is leveled off mechanically and sprinkled with water in layers up to full depth of the cell about six meters. The moisture refuse can remain in the cell for four to eight months. From the cells, the compost material is dug out by traveling grab cranes and is then screened. The material passing through the screen is pulverized, giving an earthy odourless product. This process is cheap. It is essentially an adaptation of Indore process.

4.15.9. Windrow Systems Composting is done in open by placing the refuse in elongated piles, i.e. windrows {Figure 4.18 (a, b, c)}. Periodically the piles are turned such that all particles are exposed to comparable condition at some time during the active period of the compost process. Windrow may be of any convenient length, but the depth of the pile is somewhat critical. If piled too high, the material will be compressed by its own weight, pore space will be lost, and the mass will become anaerobic. A pile that is too shallow loses heat rapidly, and is unable to attain optimum temperatures for thermophilic organism. In addition, loss of moisture is excessive, especially near the edges of the pile and the rate of composting is thereby retarded (Fuchs and Cuijpers, 2016). For convenience of turning, the initial width of the windrow should not exceed 2.4 to 3.0 meter at the base. In dry weather, the cross-section is usually made trapezoidal, with the top width governed by the width of the base and the angle of the repose of the material which is around 30° from the vertical. In rainy climate and wet weather the cross-section of the windrow should be approximately semi-circular like a haycock to shed water other than the maximum and minimum heights of pile, there is nothing critical about the stacking of ground refuse for composting.

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Fig. 4.18 Windrow System Source: Conceived from Misra et al. (2016), Fuchs and Cuijpers (2016)

4.15.9.1. Turning Since aeration in windrow composting is accomplished by turning, the pile is turned frequently so as to obtain the rapid, nuisance-free decomposition characteristic of the thermophilic aerobic process. Uniform decomposition essential for rapid composting is ensured by turning the outer edges into the center of the pile at each turn. Secondary reasons for a turning operation might be the reduction of the initial moisture content and reclamation of a compost pile has become anaerobic. The frequency of turning and the total number of turns required during the composting process are governed largely by the moisture content. The data for turning schedule for various plants are not available. However, the following turning schedule may be followed for municipal refuse. •

Moisture 60 to 70%: Turn at two-day intervals; approximate number of turns 5.

•

Moisture 40 to 60%: Turn at three-day intervals; approximate number of turns 4.

•

Moisture below 40%: Add moisture.

If the moisture content is more than 70% turn every until the moisture content is reduced to less than 70%. Then follow the above schedule. Turning basically speeds up the composting. Where time is not an important constraint, the turning schedule can be modified to allow longer intervals between turnings. However, turning accelerates nitrogen loss.

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73

Moisture Control

The control of moisture in windrow composting may range from eliminating excess moisture to applying water when a pile becomes too dry. Moisture can be controlled with varying degree of effectiveness by adding straw, dry soil, saw dust etc. However, care must be taken to see that C/N ratio does not increase unduly. The recommended remedy for excessive moisture is frequent turning which bring about a reduction in moisture content without distributing the C/N ratio. In area having heavy rainfall, material composted in open may become excessively wet. In such case, preventive measure like sheltering the piles with a roof should be taken. Research has indicated that rain penetrate only 3 to 6 mm when composting material is subjected to a heavy rainfall. Sprinkling water with a hose produces similar results. The water merely flowed off the piles without penetrating them. To increase the moisture content of a pile, water can be added more frequently during the turning operation. The exposed material absorbs water. The outer part of the unsheltered piles dry out during sunny weather, in which case surface sprinkling should be practiced to promote uniform decomposition.

4.15.11.

Pit Method

The walls and the bottom of the pit are lined with brick or masonary, or the natural earth is tamped and packed. The walls of unlined pits are apt to crumble resulting in pit acquiring irregular shape. The material is staked to a height of 30 cm or more above the ground making a total depth of 0.9 to 1.4 m. The material can be turned in the pit as often as necessary to provide the high temperature and aerobic conditions required (Fuchs and Cuijpers, 2016). When the pits are used, a smaller stack surface is exposed to air, and the walls and bottom of the pit provide some insulation against the heat and moisture loss. The pit may be provided with a chimney and trenches or a porous bottom for aeration and drainage of liquid seepage from the pile. It is suggested that composting in pits approximately 0.9 m deep by a system of providing aerobic conditions and high temperature for the first few days and the anaerobic condition for four to five months. The material is stacked in the pits in the layer with at least 15 - 22 cm of refuse on the top. There is sufficient oxygen in the initial stack for a high temperature to be produced by the aerobic organisms during the first few days. Apparently, the high temperature is retained for some two weeks, owing to the insulating properties of the stack, even though anaerobic conditions exist after the first few days. The material is left to compost in the pit with no turning for about three months under conditions which are primarily anaerobic. As the pile settles, another layer of material is sometimes placed on top to maintain the desired depth. After it become anaerobic, dirt or other covering material may be placed on this pile to absorb the escaping nitrogen, retain the moisture and helps to prevent fly breeding. In this arrangement, the top 10 - 15cm of the material is usually not well composted. There is less assurance that sufficiently uniform and high temperatures have been developed to destroy the pathogen. In addition, the problem of controlling flies and odours of purification is serious when anaerobic conditions prevail.

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When the ground water table is high, pits cannot be used satisfactory, if they are used, drainage from the bottom of the pit is desirable and provision should to be made to prevent surface run off into the pits. The advantage of pit method is in labour saving but at the expense of more flies and odours and less certain destruction of pathogen. Grater conservation of nitrogen is achieved in pit composting.

4.16. Conservation of Nitrogen One of the most important purposes of composting organic waste is the conservation of nutrients and fertilizer value of the waste. Nitrogen conservation is very important. It is more difficult to conserve nitrogen than phosphorous, potash and other micronutrients. Nitrogen may be lost by leaching, but the major loss comes from the escape of ammonia or other volatile nitrogenous gases from the compost material to the atmosphere. Nitrogen loss as ammonia on aerobic composting as affected by the C/N ratio, the pH, the moisture content, aeration, temperature, form of nitrogen compounds at the start of composting and the adaptive or nitrogen holding capacity of the composting materials. A ratio of available carbon to available nitrogen of about 30 or more permits minimum loss of nitrogen. Various research workers have reported optimum ratio of C/N to avoid the nitrogen loss under different condition. There are three phases of relation of nitrogen supply and conservation to available carbon in biological decomposition: (a) when more nitrogen is available is low with respect to nitrogen, i.e. when more nitrogen is available than necessary for the organisms to utilize carbon (low C/N ratio), very considerable quantities of ammonia and volatile forms of nitrogen will be given off and lost; (b) When the requisite amount of nitrogen and carbon for bacterial utilization is present, decomposition proceeds without appreciable loss of nitrogen; (c) When nitrogen is low in relation to carbon, some of the organisms will die and their nitrogen will be recycled. Small additional amounts of nitrogen may be picked up by the nitrogen fixation when conditions are satisfactory. Hence, in all the three phases, there is a tendency to reach the same final amount of nitrogen-that which can be held by the bacteria when the compost is in a stabilized condition. In the first phase nitrogen is lost, in the second it is stabilized and conserved, and in third it is recycled, conserved and sometimes accumulated. This illustrates that composting of operations can be conducted to conserve most of the nitrogen in wastes. Ammonia escapes as ammonium hydroxide increasingly readily as pH rises to about 7.0. Materials which contain large amounts of ash will have high initial pH and may be expected to loss more nitrogen. Whenever possible, some of the ash should be withheld from the compost piles and after added after composting. The moisture content of the compost affects nitrogen conservation but to a much less marked extent than the C/N ratio and the pH. Ammonia escape is greater when the

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moisture is low. The water serves as a solvent and diluent for the ammonia, thereby reducing the vapour pressure and volatilization. A moisture content ranges of 50 to 70%, which is also satisfactory for other aspects of composting will assist in the conservation of nitrogen. Aeration and turning adversely affect nitrogen conversation. If ammonia is present, it will escape more easily when the material is distributed and exposed to the atmosphere. When other factors are favorable for nitrogen conservation the losses in turning will not be great. High temperature increase volatilization and escape of ammonia, since high temperature is fundamental in aerobic composting and destruction of pathogens. There is little to be done about controlling temperature other than to avoid temperature above 70oC, which retard bacterial activity and permit ammonia accumulation. Since the greatest ammonia loss occurs during the early stages of active decomposition, only little conservation of nitrogen will be gained by reducing the temperature after the first two turns or after the first six to eight days of active decomposition. If the other factors conductive to nitrogen conservation are satisfactorily maintained and the temperature is below 65oC to 70oC, the effect on nitrogen loss will be small. The form in which the nitrogen is initially present in the material may affect nitrogen conservation. If large amounts of ammonia are present in the raw materials, some of this ammonia may be volatilized and lost before the organisms have had sufficient time to utilize and stabilize it, even though C/N ratio is satisfactory for nitrogen conservation. This can be an important factor since much of the nitrogen loss occurs during the first few days of composting. Loss of nitrogen by leaching may occur in rainy weather, or if the composting material has too high an initial moisture content, the excess of liquid drains away. Loss of leaching depends on the amount of soluble nitrogen in the compost and on the rainfall. Leaching may be minimized by preventing water from entering the compost stack. To provide more nitrogen in composts of low-nitrogen materials such as cotton and sorghum stalks, sugarcane trash, or other material rich in cellulose, Jackson and his colleagues suggested planting leguminous sun-hemp, Crotalaria juncea or other nitrogen fixing plants on old compost stacks to add nitrogen by fixation. There is very little loss of nitrogen during the storage of compost except when the compost contains large amount of ammonia. Anaerobic composting may conserve more nitrogen than aerobic composting.

4.17. Use of the Compost Finished compost may be designated by the general term ‘humus’. When used in soil, humus has many characteristics beneficial both to the soil itself and to the growing vegetation. In conjunction with commercial fertilizers, humus exhibits certain

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additional and very desirable characteristics. Physical effects of humus on the soil are more important than the nutrients effects. Soil structure may be as important to the fertility as is its complement of nutrients, soil aggregation or crumb tendency as promoted by humus improves the air-water relationship of soil, thus increasing the water retention capacity and encouraging more extensive development of root systems of plants (Vera et al., 2016; Misra et al., 2016). Aggregation of soil particles is brought about by cellulose esters (cellulose acetate, methyl cellulose and carbomethyl cellulose) resulting from bacterial metabolism. Other beneficial effects of bacterial metabolism associated with humus include an increased ability of the soil to absorb rapid changes in acidity and alkalinity and the neutralization of certain toxic substances.

4.18. Characteristics of an Ideal Compost The characteristics of ideal compost are as under: (i)

It should be dark brown to black, with little or no particles of the original organic residue present.

(ii)

The organic matter content should be at least 80% (oven-dried basis).

(iii)

The field moisture content should range between 10 and 20%.

(iv)

The compost should have water-holding capacity of 150 to 200%.

(v)

Ash content should be 10 to 20%.

(vi)

The total nitrogen content should be 2.5 to 3.5%.

(vii)

The total P2O5 content should be 1 to 1.5%.

(viii) The total K2O content should be 1 to 1.5%. (ix)

The cation-exchange capacity should range between 75 to 100 miliequivalent per 100g.

(x)

The pH value should be between 5.5 to 6.5.

(xi)

The nitrogen availability value should range from 50 to 70% of that of ammonium sulphate.

(xii)

Odour should be slightly musty.

It is expected that not all the compost will fit the characteristics of the ‘Ideal Compost’. Unquestionably, the most important characteristics including total nitrogen, nitrogen availability, total P2O5 and total K2O should be met.

4.19. Methods of Composting for Villages and Small Towns Sanitary composting can be done practically cheap, involving much less capital expenditure. The compost made from organic rubbish, night soil, garbage and other organic wastes from villages and towns has approximately the same fertilizer qualities as farmyard manure. While designing a system for villages and small towns

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it may be borne in mind that primarily hand labour will be utilized and that little mechanical equipment will be required for handling the relatively small amounts of wastes. Composting wastes from villages is usually economic only where labour costs are low or where the farmers themselves conduct the composting operation either on their farms or cooperatively. Grinding or shredding of the wastes, or mechanical removal of metal glass, plastic and other non-compostable materials, is not necessary in composting waste from village. Tractors or bullocks may be used for moving materials to the depot and labour is generally used for stacking the materials or placing in pits, sorting out noncompostable materials and turning for aeration. The methods for composting organic wastes which has proven most satisfactory for use in villages and small towns in different parts of the world are basically modifications of the Indore process. The technique involves placing the compostable matter in pits and in stacks on the ground and, usually, turning the material to provide aeration. In the various techniques now used extensively in small-town composting, some features of the pit or stack method for placement of the material are adapted or modified and the amount of turning for aeration and fly control varies from no turning at all to several turns during the composting period. Pits are more expensive to build but are somewhat cheaper to operate. The placement and turning of the compost in stacks involves an increased labour cost for material handling. The cost of turning is major part of the operating costs. However, minimizing or eliminating turning is often at the expense of less satisfactory fly control, less efficient decomposition, less certain destruction of pathogens and parasites, and odour nuisance. The composting of village refuse without the addition of night soil or sewage sludge can be conducted with less careful control than can the composting and parasitic organism. The material can be dumped from the collection vehicles into pits or stacks and requires only a limited amount of handling.

4.20. Selection of Composting Method The selection of a method for composting village or small town wastes depends upon the character of the wastes, the features of the compost site, the climate and on whether the finished product is to be used on farm, market garden, nurseries or lawns. The important aspects in the selection and use of method are sanitary and nuisance control and costs. The method of composting in pits has advantage of confining the materials during the composting to a fixed container, thereby reducing the hazards which may result from careless workmen distributing night soil around the compost depot when stacking and turning the material. The initial cost involved in building a compost in the pits is not turned the operation cost will be low, but greater number of pits and larger capital expenditure required may nearly offset the labour saving. Composting the material in pits without turning, results in greater fly and odour problem; besides

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the pathogens and parasites need not to be fully destroyed. Pits do provide better heat insulation of the composting material which is useful in cold climates-but for this reason they also provide less opportunity for natural ventilation or aeration – a drawback in warm climates (Misra et al., 2016). It is usually desirable to turn and aerate the composting materials. When hand labour is used, turning and fly control can probably be accomplished a little more cheaply in the walled pits than in the stacks. The stack method offers greater flexibility for adaption and changes in operations with varying conditions. Low initial capital cost is an important factor in the establishment of a composting programme. Stacks permit better natural aeration and often develop high temperature so that composting is more rapid. Where turning is practiced the stack, technique may require slightly more land than pit method. The stack method is more satisfactory than the pit method when the wastes to be composted contain no night-soil.

References Basu, P. (2013). Biomass gasification, pyrolysis and torrefaction: practical design and theory, (2nd Edition), Academic press, Elsevier, 32-Jmaestown Road, Lodon, UK. Brown, M. L., Bulpitt, W. S., Walsh Jr, J. L., and McGowan, T. F. (2011). Biomass and alternate fuel systems: an engineering and economic guide: John Wiley and Sons. Hobken, New Jersey, Canada. Conway, R. A., and Ross, R. D. (1980). Handbook of industrial waste disposal: Van Nostrand Reinhold New York. Fuchs, J. G., and Cuijpers, W. J. (2016). 2 Compost types, feedstocks and composting methods. Handbook for Composting and Compost Use in Organic Horticulture, BioGreenhouse COST Action FA 1105. Gaeta-Bernardi, A., and Parente, V. (2016). Organic municipal solid waste (MSW) as feedstock for biodiesel production: A financial feasibility analysis. Renew. Energy, 86, 1422-1432. Gupta, V. K., Carrott, P. J. M., Ribeiro Carrott, M. M. L., and Suhas. (2009). Lowcost adsorbents: growing approach to wastewater treatment—a review. Crit. Rev. Environ. Sci. Technol., 39, 783-842. Panda, H. (2011). Manufacture of Biofertilizer and Organic Farming, Asia Pacific Business Press, 106-E, Kamla Nagar, Dehli-110 007, India. Huber, G. W., Iborra, S., and Corma, A. (2006). Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. Chem. Rev., 106, 40444098. Insam, H., Riddech, N., and Klammer, S. (Eds.). (2013). Microbiology of composting. Springer-Verlag Berlin Heidelberg New York., USA. Jilani, S. (2007). Municipal solid waste composting and its assessment for reuse in plant production. Pak. J. Bot., 39, 271-277. Kumari, R., and Grover, I. (2007). Waste generated and adoption of waste management practices among rural households in Haryana. J. Hum. Ecol., 22, 355-360.

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Li, C., Zhao, X., Wang, A., Huber, G. W., and Zhang, T. (2015). Catalytic transformation of lignin for the production of chemicals and fuels. Chem. Rev. 115:11559-11624. McKendry, P. (2002a). Energy production from biomass (part 1): overview of biomass. Biores. Technol., 83, 37-46. McKendry, P. (2002b). Energy production from biomass (part 2): conversion technologies. Biores. Technol., 83, 47-54. Menon, V., and Rao, M. (2012). Trends in bioconversion of lignocellulose: biofuels, platform chemicals and biorefinery concept. Prog. Energy Comb. Sci., 38, 522550. Misra, R. V., Roy, R. N., and Hiraoka, H. (2016). On-farm Composting Methods. Food and Agriculture Organizatio, Rome, Italy. Qu, J.-x., Jiang, Y., He, G.-s., and Pan, Y.-J. (2004). Research on dry anaerobic fermentation by agricultural refuse. Renew. Energy, 2, 017. Saharan, B.S., Sahu, R.K., and Sharma, D. (2011). A review on biosurfactants: fermentation, current developments and perspectives. Genetic Engg. Biotechnol. J., 1, 1-14. Vera, D., de Mena, B., Jurado, F., and Schories, G. (2013). Study of a downdraft gasifier and gas engine fueled with olive oil industry wastes. Appl. Therm. Engg., 51, 119-129.

Chapter 5

Animal Waste Generated in Rural Areas Faizan ul Haq Khan, Abdul Nasir Awan and Shafique Anwar*

Abstract Animal waste generated in rural areas of Pakistan is significant. This includes excreta and by products of various animals which can be used for valuable purposes. Classification of waste generated by various livestock and their utilities are completely discussed on one hand for understanding the subject, and on the other hand methods of converting these wastes and animal protein into manure along with their manurial values are also given. Treatment of animal waste for energy generation as biogas is completely discussed. A complete knowledge on the basic theory, necessary conditions for biogas production, design and development, types of biogas plant and use of biogas is given in this chapter. In the present scenario of energy crises biogas production is one of the sources to overcome the energy crises. However, generation of biogas from animal waste is the best management and disposal techniques because biogas can be used as fuel and its residue can be used as organic manure into agricultural fields. Therefore, this is a twofold solution of the problem. Keywordss: Animal waste, cattle waste, poultry waste, manurial values, biogas.

5.1.

Introduction

Animals are the second biggest specie which supports life on the planet earth where we live. These are used for various purposes in our daily life with some advantages *

Faizan ul Haq Khan˧, Abdul Nasir Awan and Shafique Anwar Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

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and dis-advantages. As we know that human beings are responsible for waste generation in urban and rural areas, similarly animals are also responsible for waste generation. Animal waste constitutes a large proportion of waste in rural area of Pakistan. It includes excreta and by products like hides, skins, bones, hairs, horns, hoofs, tallow, lard, guts, glands, tail stumps, blood and non-edible meat waste. The major constituents of animal waste are organic nitrogen, carbohydrates, lignin and inorganic salts. The high organic content of animal waste contributes to large biological and chemical oxidation demand values. The high concentration of organic solids limits the location of an animal rearing operation, land application of waste or use of traditional waste treatment techniques.

5.2.

Animal Excreta

Part of the total animal excrement remains in the pasture and range land, but large volume accumulates in feedlots and buildings, and must be collected, transported and disposed of in an economical and inoffensive manner. The excreta voided by animals vary due to the differences in breed, age and weight, and diet. In general, the animal waste to be handled for economical disposal may be anyone of the following things: (a) Fresh excrement including both the solid and liquid portions, (b) Total excrement but with bedding added to absorb the liquid potion, (c) The material after liquid drainage, evaporation of water, or leaching of soluble nutrients, (d) Total excrement mixed with spilled fodder, (e) Only the liquid which has been allowed to drain from the total excrement, (f) Material following aerated or anaerobic storage. The characteristics of these items may be different. The moisture content of fresh waste depends on the type of feed and environmental temperature and humidity. Evaporation of water may occur under certain conditions. Addition of water occurs from rain water, wash water, incidental spillages from drinking nipples or troughs or water added to increase the flow and pumping characteristics of the wastes. When estimating the volume of waste to be handled, it is important to include added water content and bedding material. The added water can contribute significant volumes of water to the overall waste collected. The decision as to whether to handle the waste as slurry or solid depends upon how much extraneous water is allowed into the system. Solid management requires adequate absorbent bedding, sufficient roof cover and properly channeled surface water run-off, a slurry system using frequent washing by hose or sluice and little or no bedding produces a higher volume of waste to be collected and handled.

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5.3.

83

Effluent Classification

Livestock effluent may be divided into four main classes according to the percentage of dry matter is given in Table 5.1. (Bernet, 2009) Table 5.1 Classification of Livestock Effluent based on Dry Matter Type of Effluent Liquid Semi-liquid Semi-solid Solid

Maximum dry matter (%) 10 20 30 50

Source: Bernet (2009)

The dry matter content is important for two reasons: (i) Water can be evaporated, leaving the dry matter as the pollutant. (ii) If water can be excluded, the solid is cheaper to handle and store since it needs less space. Physical and chemical tests reveal dry matter content and its constituent parts. The basic analysis and classification of an effluent determines, subject to certain interrelated restraints, the practical methods for its handling and storage. Solids are more expensive to handle since their bulk is greater than that of liquids in relation to manurial value. Moist soils tolerate a greater density of application of solids than to liquids and pollution problems are less likely to arise. Against this benefit, unless the manure is ploughed in, soon after distribution, much of its value may be lost by leaching. The decision to use solids can depend also on the type of bedding desired for livestock, the availability of straw or the need for humus additives to the soil. Semi-solid effluents are rather easier than are solids to transport and spread, but at 15% or less dry matter content, they are semi-liquid and need water-tight containers. Wastage spilled in transit can be unpleasant and if on the highway, constitutes an offense. Lifted effluent transported in open top trailors or spreaders can be offensive, when taken through village streets. Handling and disposal of liquid effluent requires an approach completely different from that of either solids or semi-solids. The advantages of liquids are that they can be handled by gravity or under pressure and that the actual volume handled per head of stock is less, unless subsequently diluted by water. Vehicles need not go on to the land if a wide-throw tanker spreader or organic irrigation is used. An additional advantage is that liquid effluent can be injected directly into the soil with benefit both to manurial value and to hygiene. The disadvantages, unless the effluent is pretreated, include odour, quick soil run off and ponding together with other pollution risks.

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F.H. Khan, A.N. Awan and S. Anwar

Particle Size Distribution

Classification of livestock wastes based on particle size distribution is given Table 5.2. The particle size of livestock waste has definite effect on chemical and biological properties. Under aerobic stabilization, finest fraction of waste gets decomposed to the great extent. The coarsest fraction is the least degraded. The nitrogen enriched fine fraction is best suited for fertilizer use (Tables 5.3, 5.4, 5.5). Table 5.2 Particle-size Classification of Livestock Wastes Livestock Nature of the wastes

No. of sample analyzed

Dairy

Greater than 1.000 mm 56.9 67.7

Particle size distribution (percent total) 1.0000.5000.2500.1050.500 0.250 0.105 0.053 mm mm mm mm 19.9 13.8 5.2 2.3 12.4 10.8 6.6 2.1

Deposited 5 Com posted 2 Collected fresh 3 41.8 7.1 Beef Deposited 3 65.4 16.1 Cattle Collected 3 30.7 9.0 fresh Poultry Deposited 3 15.2 29.3 Composted 1 48.9 37.7 Collected 3 23.6 11.6 fresh Fresh dried 1 52.7 21.0 Source: Møller et al. (2002), De La Fuente et al. (2013)

Less than 0.053 mm 0.9 0.4

7.2 10.1 6.7

3.9 5.3 6.1

2.0 1.6 3.6

38.0 0.5 43.9

25.0 9.6 16.3

16.2 2.5 8.3

8.5 8.5 4.8

6.5 6.5 35.6

15.1

8.1

2.6

0.4

Table 5.3 Plant Nutrients and Heat of Combustion Values of Dairy Wastes Nature of the wastes

Particle size (mm)

Deposited

>1.000 1.000-0.500 0.500-0.250 0.250-0.105 0.105-0.053 1.000 1.000-0.500 0.500-0.250 0.250-0.105 0.105-0.053 1.000 1.000-0.500 0.500-0.250 0250-0.105 0.105-0.053 1.000 1.9 1.000- 0.500 1.9 0.500-0.250 2.1 0.250-0.105 2.2 0.105-0.053 2.3 1.000 1.7 collected 1.000-0.500 2.2 0.500-0.250 2.5 0250-0.105 2.7 0.105-0.053 2.8 1.000 1.000-0.500 0.500-0.250 0.250-0.105 0.105-0.053 1.000 1.000-0.500 0.500-0.250 0.250-0.105 0.105-0.053 1.000 1.000-0.500 0.500-0.250 0.250-0.105 0.105-0.053 >0.053 >1.000 1.000-0.500 0.500-0.250 >0.250

Com posted

Fresh collected

Fresh dried

Nitrogen (Percent Dry Weight) 4.2 3.7 3.9 4.9 6.0 7.2 3.1 3.1 3.1 3.3 3.8 4.7 4.4 3.5 4.4 7.1 4.7 9.1 5.3 4.9 4.1 4.8

Phosphorous (Percent Dry Weight) 0.26 0.25 0.81 0.45 0.54 0.29 0.75 0.79 0.55 0.60 0.48 0.79 2.15 2.19 1.91 2.54 3.35 0.55 0.85 0.71 1.15

*Not Analyzed Source: Møller et al. (2002), De La Fuente et al. (2013)

Heat of combustion (kcalg-1) (Dry Weight) 3.5 3.4 3.3 2.8 2.5 2.5 2.4 2.5 1.7 1.8 1.0 1.9 * * * * * * 3.1 2.8 2.2 2.5

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Composted wastes, which are most stable biologically, always have lower nutrient value. The crude fiber content decreases while crude protein and ash content increase with increase in fineness of waste particles (Tables 5.6, 5.7, 5.8). If protein content is used as a criterion to select feed supplements, a finer fraction with high protein content is a better choice. Because of their higher protein content, poultry wastes probably have a greater value as feed supplements than do beef and dairy cattle wastes. In general, fresh wastes have the highest value for reutilization as fertilizer, feed supplement or fuel. Table 5.6 Feed Values of Dairy Cattle Wastes Nature of Particle size Moisture Crude the waste (mm) content fiber (%) (%)

Crude protein (%)

Fat (%)

Nitrogen free extract (%)

Ash (%)

Estimated gross energy + (kcal g-1)

>1.000

12.0

23.8

12.5

1.39

21.4

28.9

3.2

1.000-0.500

10.9

25.7

12.5

0.65

22.4

27.6

3.1

0.500-0.250

8.2

19.5

12.6

0.65

27.3

31.8

3.0

0.250-0.105

9.8

12.4

14.0

0.67

25.7

37.5

2.7

0.105-0.053

8.2

10.5

14.6

1.35

21.4

43.9

2.5

1.000

12.3

14.4

7.3

0.71

11.3

5.0

1.8

Composted 1.000-0.500

10.7

13.2

7.9

0.69

13.3

54.2

1.8

0.500-0.250

7.4

8.6

5.3

0.59

12.7

65.4

1.3

0.250-0.105

5.0

6.1

4.7

0.44

10.3

73.3

1.1

0.135-0.053

3.2

5.4

5.1

0.36

8.7

77.2

1.0

1.000

*

41.8

11.4

3.15

1.000-0.500

*

33.8

12.4

-

0.500-0.250

*

35.4

10.2

3.25

40.9

10.2

4.2

0.250-0.105

*

27.7

17.2

3.82

40.0

11.3

4.2

0.105-0.053

*

11.7

23.9

7.41

37.1

19.9

4.1

< 0.053

*

4.4

29.0

12.92

16.7

37.0

3.8

*On dry weight basis + Calculated on dry weight basis by assuming 4.3 kcal g-1 for crude fiber and nitrogen free extract 5.6 kcal g-1 for crude protein 9.3 kcal g-1 for fat Source: Møller et al. (2002), De La Fuente et al. (2013)

4.2 -

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Table 5.7 Feed Value of Beef Cattle Wastes Nature of the waste

Particle size (mm)

Moisture content (%)

Crude fiber (%)

Crude protein (%)

Fat (%)

Deposited

> 1.000 1.000-0.500 0.500-0.250 0.250-0.105 0.105-0.053 1.000 1.000-0.500 0.500 -0.250 0.250-0.105 0.105-0.053 1.000 17.8 9.8 15.4 23.4 1.85 1.000-0500 25.0 8.8 15.7 24.1 1.17 0.500-0250 24.5 8.8 13.7 30.6 2.03 0.250-0.105 16.2 8.9 8.8 27.7 2.15 0.105-0.053 9.0 < 0.053 7.3 7.3 45.1 3.10 Composted > 1.000 11.6 17.9 19.2 0.89 10.3 1.000-0.500 11.7 17.3 19.1 0.56 7.4 0.500-0.250 4.0 11.4 16.1 19.2 0.86 0.250-0.105 1.0 8.5 12.1 20.4 1.25 0.5 0.\05-0.053 7.4 10.4 23.9 0.65 < 0.053 10.3 9.4 29.2 0.75 Fresh > 1.000 * 29.9 27.9 0.97 14.4 collected 1.000-0.500 * 24.1 22.0 1.24 33.6 0.500-0.250 * 23.7 27.8 1.55 30.6 0.250-0.105 * 18.8 34.3 2.58 23.7 0.105-0.053 * 17.4 29.5 < 0.053 1.7 56.7 3.20 * 8.1 Fresh dried > 1.000 3.3 12.0 33.3 2.44 19.4 1.000-0.500 2.8 13.1 30.7 2.25 15.4 0.500-0.250 2.2 10.7 25.7 2.96 15.5 < 0.250 2.7 11.2 38.2 3.22 5.8 *On dry weight basis + Calculated on dry weight basis by assuming 4.3 kcal g-1for crude fiber and nitrogen free extract 5.6 kcal g-1 for crude protein 9.3 kcal g-1 for fat Source: Møller et al. (2002), De La Fuente et al. (2013)

5.6.

Ash Estimated (%) gross energy + (kcalg-1) 31.9 3.2 24.5 3.6 25.7 3.5 28.7 3.5 33.5 3.9 34.7 3.4 40.1 2.7 43.9 2.5 48.4 2.3 55.9 2.0 57.1 2.0 53.5 2.4 26.8 3.6 19.0 3.8 16.7 4.0 20.6 4.0 16.0 30.3 3.9 29.6 3.4 35.7 3.2 42.9 2.8 38.9 3.2

Poultry Waste

Fresh poultry manure contains 75 - 80% moisture, 15 - 18% volatile solids and 5 7% ash with an average particle density of 1.8 and a bulk density of about 1.04 gcc1 . About 50% of solids are finer than 200 mesh. Manure excreted from a chicken per day represents about 5% of the body weight of the bird. Waste volume ranges from 0.220 to 0.270 liter per bird per day. The poultry litter has about 1.90% nitrogen, 1.8% phosphorus and 1.2% potassium. However, these values may vary depending upon the feed ration (Moreki and Keaikitse, 2013). Pollutional characteristics are of value when estimating the effect of poultry waste on land and water resources but available data vary. European data indicate a BOD concentration of 100 gL-1for fresh poultry manure.

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89

Swine Waste

The waste production from a hog depends upon the type and size of animal, the feed, the temperature and humidity within the building and the amount of water added in washing and leakage. The availability of quantity of faeces and urine increases with weight and food intake of the animal. The feeding regimes will affect the properties of the pig manure. Pig manure has about 0.53% nitrogen, 0.53% phosphorus and 0.36% potassium. Approximately 30% of the consumed feed is converted to body tissue and the, remainder is excreted as urine and manure. The manure production per day ranges from 6-8% of the body weight of a hog. The average volume of manure production is about 1 liter per 10 kg animal per day. Wet manure can contain 5-9% total solids; of these 83% may be volatile. Swine waste, stored anaerobically gives out offensive smell, when exhausted from a building or spread on the land. Nutrients in the wastes are of utmost importance because the land is the ultimate acceptor of the waste.

5.8.

Disposal of Animal Waste

Most of the animal wastes have good manurial value as soil conditioner. The basic plant nutrients brought in as fertilizer are nitrogen (N2), phosphorus (as P2O5) and potassium (as K2O). An animal excreta contains these nutrients in varying degrees. The minor nutrients or trace elements, essential for correct growth, are also present in minute quantities. These basic nutrients are readily identified in the laboratory. Humus contents and its value to the soil are more complex matter.

5.9.

Manure Management Information

There are essentially two problems the farmers should face with manure. The first relates to the timing animals defecate every day of the year. Manure can be disposed of only at certain times. It can be spread on the land, only when the land and the crop are ready for it. The manure must be collected, transported, stored and processed so that until it can be properly utilized discharged, it does not cause environmental problems. This leads to the second part of the problem. Manure is such a low-value commodity that the investment and attention necessary to collect, store and process it, should be minimal (Bernal et al., 2009). The cheapest place for a feedlot operator to store manure is in the corral where it is defecated. If the manure in storage on the corral gets washed (transported) into a stream to degrade the receiving water, unit operations are to be performed so that the discharge of the material to the environment is more acceptable. The key to the sanitary, economical and efficient manure management procedure is based on the practice of ‘keeping the manure out of water and keeping the water out of manure’.

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5.9.1. Manurial Value The quality of animal residue depends on several factors. The handling of manure before use has the largest effect on the constituents. The manure is handled as a solid, slurry or liquid Figure 5.1.

Fig. 5.1 Typical Manure Management Systems used by the Livestock and Poultry Industry The quantity of dry matter available may increase if bedding is added and if the manure is stored on an outdoor unpaved lot. Similarly, the volatile solids and total solid contents are drastically different depending on the types of systems used. The manure residue from an unpaved beef cattle lot has less volatile solids since the soil in the residue is high in inorganic solids. In contrast the volatile solids of beef cattle manure from a bedded pack are extremely high since the straw or bedding contains a high portion of volatile solids. Dairy cattle manures may be handled as liquid slurries, semi-solid slurries and semisolids with bedding. Conditions within stored slurries or semi-solids range from highly aerobic to almost totally anaerobic. Beef cattle manures are most likely to be stored in situ in covered or partially open yards. Conditions within the mass of manure are superficially aerobic with deeper layers almost completely anaerobic. Pig manure is almost invariably handled as slurry, with little bedding material. Poultry manure from caged layers is handled either as a semi solid as formed or may be slurried with water for transport. Most broiler chickens are housed on litter which is removed at the end of each production cycle. The resulting material is relatively dry and suffers almost no leaching loss prior to removal, but losses of nitrogen by denitrification may be quite high. For those manures handled as slurries, anaerobic digestion appears to offer a dual benefit. The digestion releases some usable energy and under ideal conditions, results in no loss of nitrogen. Wide use of this technique could save sufficient quantity of nitrogen.

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Design of animal waste handling system should have following features: (i) It should provide sanitary conditions; (ii) There should be no nuisance of odour; (iii) It should provide an efficient and effective methods of handling waste; (iv) Installation and operational costs should be minimum; (v) The system should be able to maintain high nutrient value of waste. As per estimate about 2/3 N 1/2 P and all K is available immediately in case of cattle and pig slurries while about 4/5 N, 1/2 P and all K is available from poultry manure. The residual nutrients are slowly released from their complex organic molecules over several years by bacterial action in the soil. Up to 50% and more of the nitrogen in fresh manure may be in ammonia form or be converted to ammonia in a very short time following excretion. Free ammonia is very volatile and may escape into the air if not absorbed by or reacted chemically with some substance. Organic nitrogen compounds also enter the atmosphere from beef feed lot surfaces. The ammonia in manure may oxidize to nitrites and nitrates under aerated conditions. If gaseous nitrogen is produced by these nitrites and nitrates, it may escape into the air. Soluble forms of nitrogen may be leached by water passing through manure stored in outside sites on uncovered feedlot surfaces. While making accurate estimates of nutrient losses is nearly impossible, using available information from a wide variety of experiments the data on expected losses showing enough consistency has been compiled in Table 5.9. Table 5.9 Estimated Nutrient Losses during Storage, Treatment and Handling for Various Waste Management System System

N2

Nutrient loss (%) P 2O 5 K 2O

Deep pit storage, liquid spreading

30 to 65

-

-

Anaerobic lagoon, irrigation or liquid spreading

60 to 80

30 to 50

*

Oxidation ditch, anaerobic lagoon, irrigation or liquid spreading

70 to 90

*

*

Bedded confinement, solid spreading open lot, solid spreading. run off

30 to 40

-

-

Collected and irrigated

50 to 60

*

*

*Losses are likely but enough data are not available Source: Oenema et al. (2007)

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Phosphorus may be lost due to the formation of phosphorus containing precipitates in anaerobic treatment and storage facilities which then settle to the bottom sludges. Potassium may also be lost to the bottom sludges. Both phosphorus and potassium are subject to a certain amount of leaching loss due to precipitation on outdoor storage facilities and feedlot surfaces.

5.9.2. Humus Content The organic bulk of manures undoubtedly confers some benefit to the soil structure. The ability of humus to promote a granular structure in soils depends upon its action as a binding agent in both physical and chemical terms. The exact action depends upon the soil type. Manure can provide a free of cost (except spreading cost) supply of humus to promote free aeration and drainage, a source of nutrients and a buffer against fluctuations in soil moisture and soil structure. Treatment of Animal Waste for Manure Most farmers appreciate the value of animal manure as a fertilizer. Under Pakistani farming conditions use of farmyard manure is very popular. The simple method of spreading the waste over the land affords a very efficient treatment process that of the soil ecosphere absorbing, using and changing those wastes. From the point of view of farm management, however, it may be necessary to pretreat wastes because land spreading is either undesirable or impossible. Intensive units may simply have no land at all, or so little land that any spreading would soon saturate the ground. The farmers use their own animal waste without properly composted or purchase from the owners of animals who have no lands. However, it is very much desirable to follow the scientific method of composting for various reasons. Composting by correct techniques will: (a) (b) (c) (d) (e) (f)

Produce a humus which has a C/N ratio satisfactory for the application to the soil, Kill weed seeds, Effect maximum conservation of nitrogen, phosphorus, potash and other nutrients, Destroy pathogenic organisms, Reduce fly breeding on the farms, and Provide a means for the sanitary disposal of farm wastes.

Composting in stacks and pits is the most satisfactory way of controlling, processing and storing farm manures. The size and number of pits or stacks to be used depends on the amount of manure and waste available. Farms with 1-4 animals should provide for only one pit or stack of sufficient size to contain the manure for approximately 56 months in cold climates and 3-4 months in warm climates. Farms with a larger number of animals should have two or more pits or stacks so that one can be finishing compo sting during the period when the other is being filled. A stabled horse or cow will produce 10-16 tons of manure per year. A compost pit can be built of concrete or masonary. It may either be sunk in the ground or placed on the surface. The walls prevent surface drainage from entering

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the stack and leaching cut valuable nutrients, and also permits the retention of any liquid drainage from the manure, which contains large concentrations of dissolved nutrients. An outlet may be placed in the corner of the pit to permit the drainage to flow into a concrete or masonary sump. The walled pit also helps to control flybreeding and prevents pieces of manure and litter from being scattered around the ground by chicken or other birds. The sides of the manure piles can be nearly vertical when there is sufficient straw and litter in the manure to allow stacking. The top should be slightly rounded to turn rain water and prevent seepage through the stack. The sump for collecting liquid drainage should have sufficient capacity and preferably be lined with concrete or masonary. Filling with straw or other organic litter with a high cellulose content will serve to absorb the liquid and provide a medium for bacterial utilization of the nitrogen, thus preventing its escape as ammonia to the atmosphere. Layers of soil 5-8 cm thick and between about 20 cm layers of straw also help in absorbing the drainage and preventing the escape of nitrogen. The organic litter should be removed from the sump and placed in the compost pile when it has become saturated with the liquid. The urine from the stable should be drained either to the sump of the compost pit or to a separate sump, constructed in the same manner as the pit-drainage sump, at an appropriate place to intercept it. If there is insufficient straw and other organic litter available to provide adequate absorption and retention of the liquid drainage from the manure pile and the stable urine, a large liquid-tight sump depending on the number of animals and the rainfall, should be used to collect and contain all the liquid manure. The liquid from the sump should be removed as necessary and sprayed on the land. Since this liquid contains large concentrations of chemical nutrients, it should not be wasted. Absorption of the liquid by litter waste is usually more satisfactory from the stand point of maximum conservation of nutrients and development of soil humus. However, most of the nutrients can be recovered from the liquid by spraying it on the fields. The other method of compost is by stacking. The size of the stack is determined by the amount of organic waste material available and the time the material will remain in the stack. It is desirable to have a concrete or masonary slab under the stack and a sump for catching the drainage. If the cost of the slab is too high, a reasonably satisfactory base for the stack can be made by packing the ground surface and if possible, placing on top a layer of packed clay which will be relatively impervious. The ground should be sloped so that any drainage from the stack can be caught in a small sump, filled with straw or other litter to absorb the nutrients. If the manure is placed on a concrete or masonary slab, a 15-cm deep channel can be made in the slab around the edges of the manure stack to trap fly larvae and pupae which move to the outer edges of the stack to escape the high temperature. The inside edge of the channel should be raised about 2-3 cm so that drainage from the stack will flow to the sump and not enter the channel. The channel is kept filled with water in which the larvae are trapped.

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5.9.3. Solid-liquid Separation Solid and liquid may be separated. Solids may be used for bedding and liquid may be pumped to nearby lands. The separated solids are the undigested feed particles, straw, hay stems, silage, etc., that add bulk to manure. They make pumping difficult and tend to plug irrigation systems. Whole cow manure is difficult to irrigate, but when solids are removed from the mixture, the liquid is easily managed. The solids have several possible uses. These may be readily used for bedding in free stalls and loafing areas, and make a good soil conditioner. Although the status is not clear about re-feeding, the solids appear to be a material that may be re-fed to certain ruminant animals for bulk and roughage feed. On large farms in western countries the liquid manure is pumped and hauled with one tank wagon and tractor.

5.10. Manure Pumps and Outside Manure Storage For the storage of manure a concrete tank under the barn and barnyard may be used. Manure is either scrapped to this tank by a tractor scraper or barn cleaner, or in case of slatted floor barns it falls directly into the tank after being worked through the slots. At appropriate time, the contents of the tank are agitated and pumped out for land spreading. Earthen storage basins are successfully used for storing liquid manure. These storage bins are sometimes referred to as storage lagoons. They are not designed and managed to provide degradation and treatment of manure. Commercially available large area hollow piston and solid piston pumps may be used to move manure through underground pipe to storage basins.

5.10.1. Industrial Utility The animal waste has very little industrial value. However, manure can be used to provide protein for feeding to animals. Feeding or recycling of faecal matter back to animals is gaining widespread acceptance in the light of increasing feed costs (Jayathilakan et al., 2012). Use of manure as feed requires satisfaction of several subcriteria. Some of these are as follows: (i) Residues of potentially harmful substances and residues of indigestible materials which would rapidly accumulate in recycling in manure should be removed before its use as a feed. (ii) Manure can contain pathogens, and safety against infection can only be assured through continuous thermal and/or chemical processing. (iii) The feed products must be palatable to livestock and possess good 'shelf life' in storage and in the feed bunk. (iv) Since on-farm livestock will not consume all manure derived feeds produced, some of them should be in the form of readily transportable and marketable products if all the manure is to be so utilized. There are four basic technologies for the use of manure as a livestock feed:

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(i) Whole manure drying, (ii) Waste-ledge system, (iii) Fractionation with partial recovery, (iv) Fractionation with full recovery.

5.10.2. Whole Manure Drying In arid areas of the world air-dried manure is directly used in feed rations. Since there is no pathogen control, this is not a feasible technology. Dried poultry waste (DPW) is dried with a rotary drier and used as feed. Costs of production depend upon the moisture content of the manure. The very dry state of the feed inhibits biological activity and chances of infection are rare. Waste-ledge System The Waste-ledge system consists of blending 40% wet (70-80% moisture/manure) with dry standard feed ingredients and then ensiling the mixture for over 10 days. The pH drops to near 4.0. This acidic state, while not theoretically sufficient to ensure destruction of all possible pathogens, certainly destroys most and inhibits biological activity throughout the feed cycle. This system utilizes only about 25% of manure produced and does not present an opportunity for utilization for all the manure produced.

5.10.3. Fractionation with Partial Recovery In these systems manure is washed and settled and one or the other fraction is re-fed. Swine manure is treated in an oxidation ditch and the protein containing water is fed to swine as drinking water. Though excellent feed results may be obtained, biological control is not possible is this wet, basic medium. In another process, dilute solutions of manure are screened and then fibrous fraction is pressed and chemically sterilized for cattle feed as a roughage replacer in the ration. The liquid fraction is then pumped to lagoons for eventual disposal on fields as a fertilizer. The value of the roughage feed produced in these systems is about equal to that of low to medium grade corn silage.

5.10.4. Fractionation with Full Recovery Sand is extracted from feedlot manure and the process ends with a feed product (82% of the input) in a dry-pelleted form containing about 20% crude protein, 39% cellulose and lignin and 14% ash.

5.10.5. Protein Extraction Poultry manure may be used for protein precipitation by the Alwatech process. It involves the addition of sulphonated sodium lignosulphate to manure at pH 3.4, attained by sulphuric acid addition. Air floatation is employed to recover a grease and protein concentrate. This process is severely limited by its high cost.

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5.10.6. Protein Conversion Manure introduced into a pond stimulates the growth of plankton upon which coarse fish can feed. Carp or mullet have been used for this purpose with some success. Bivalve mollusks, whose anatomy and physiology are designed to filter out nutritious particles, can be fed manure. Manure can be used in the production of algae for harvesting as a protein source. Fungi may also be raised in this way. Mucor recemosus will grow on 50% slurry and attains 35-57% crude protein content.

5.10.7. Protein Recycling Poultry manure can be recycled as a source of uric acid. The ruminant digestive system produces urea during protein degradation and the gut micro-fauna metabolize this to resynthesize protein. Once dead these micro-fauna, already present in the rumen, provide an immediate supply of protein. Constant uric gut environment leads to steady bacteria-host relationship which changes when a grass-silage diet is used. This constant uric environment, which results in better performance of the animals, can be established by feeding poultry manure. A significant proportion of nitrogen in poultry manure is in uric form. The poultry manure may be a valuable feed supplement for the ruminant diet. Cow and pig manures are not fed directly in this way since the uric acid content is negligible. The mineral content is relatively high and the trace elements can be detected. The comparison of energy content of poultry manure and other cereals show that dried poultry manure has metabolizable energy about one-third that of cereals. The cost, however, is about one quarter to one-third that of cereals. Most of the amino acids are present in poultry manure. Though the poultry manure can be effective feedstuff, some concern has been shown over arsenic content and possible pathogen transmission. The drying process will normally guarantee a sterile product safe for feeding. Salmonellae appear to be the greatest danger but none are normally detected.

5.10.8. Drying of Poultry Manure Fresh manure from cages may be automatically scraped into a horizontal screw conveyor and by means of another similar conveyor may be delivered into a trailor. The drying is performed in a flash dryer-pulverizer which can handle wet and sticky materials. All dried manure is used for feeding cattle. This can be fed at 1 to 1.5 kg per head per day.

5.10.9. Pig Manure as Animal Feed Except for the mineral content, the chemical composition of dried pig manure might suggest that it would be well utilized by ruminant. However, dry matter digestibility has been less than 30%. If pig manure with a high copper content is fed continuously over a long period, there may be adverse effects on the recipient animals.

5 Animal Waste Generated in Rural Areas

5.10.10.

97

Dairy Waste Fiber

Dairy waste fiber is the screenings extracted from liquefied fresh dairy manure resulting from hydraulically cleaned cow confined facilities. The suspended macrodebris consisting of mostly undigested roughage, seed hulls and cow hair can be removed with the help of sewage screens. Dry waste fiber is the residual fraction of manure after the readily soluble components have been washed out. Sundried dairy waste fibers can be substituted for traditional litter in most livestock confinement situations, and for mulch or growth media in many horticultural operations.

5.11. Treatment of Animal Waste for Energy Generation The animal dung cakes are used as fuel source by direct burning in most of the villages. The efficiency of utilization of the dung cakes for energy generation is only 8 - 11%. However, the animal wastes have a very rich source of energy in the form of biogas which has 55 to 75% methane (Brown et al., 2011). The use of anaerobic digestion of organic waste accompanied by the recovery of methane for fuel has been an important development in the field of science and technology. This method provides sanitary treatment of organic wastes, satisfactory control of fly breeding, efficient and economical recovery of some of the waste carbon as methane for fuel and retention of the humus matter and nutrients for the use as fertilizer.

5.11.1. Biogas Biogas is a flammable gas produced by methane-forming organisms when organic materials are fermented at a certain range of temperatures, moisture contents and acidities under anaerobic conditions. The chief component of biogas is methane which makes it burn with blue smokeless flame. Biogas is a form of biological energy that can be synthesized. In nature, there are many raw materials from which biogas can be extracted like human and animal manure, leaves, twigs, grasses, stalks of crops, garbage and also some agricultural and industrial wastes.

5.11.2. Physical and Chemical Properties of Biogas The biogas is a mixture of methane (50-70%), carbon dioxide (CO2), hydrogen (H2), nitrogen (N2), carbon monoxide (CO) and hydrogen sulphide (H2S) in traces and several other hydrocarbon compounds. Methane itself is odourless, colourless and tasteless, but the other gases contained in biogas give it a slight smell of garlic or rotten eggs. The weight of methane is roughly half that of air. The solubility of methane in water is very low. At 20 °C and 1 atmosphere only three units of methane (volume) can be dissolved in 100 units of water (Chandra et al., 2012).

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Methane has a chemical formula of CH4 and a molecular weight of 16.04. It is a very stable hydrocarbon compound. Methane and hydrogen when burnt with oxygen give energy in the form of heat, i.e. Equation 5.1. %* + 2"# → 2%# " +

"# + 233.8 ./01

2%# + "# → 2%# " + 2×68.4 ./01 Equation 5.1 – Estimated Heat Generation by the burning of Biogas The carbon dioxide in the biogas does not contribute to heat energy, indeed it is unfavorable to any burning process. The amount of heat energy generated is 8714 kcal m-3 for methane and 2798 kcal m-3 for hydrogen. On complete combustion 1 m3 of biogas can release about 5000 kcal heat.

5.11.3. Uses of Biogas Biogas can be used as a high-quality fuel for cooking and lighting. One cubic meter of biogas keeps one biogas lamp of a luminosity equivalent to a 60-watt electric light burning for six to seven hours. Biogas is also a superior fuel for producing power. One cubic meter can keep a 1 Hp internal combustion engine working for two hours, roughly equivalent to 0.6 to 0.7 kg of petrol (Chaudhry et al., 2009). One cubic meter of biogas is equivalent to 0.620 liter of kerosene, 3.474 kg of firewood, 1.458 kg of charcoal, 12.296 kg of cow-dung cake, 0.433 kg of butane and 4.698 kWh of electricity. Figure 5.2, shows the uses and equivalent of biogas (Wierzbicki, 2012) and Table 5.10 presents the comparison of various fuels (Brown et al., 2011). Table 5.10 Comparison of Various Fuels Name of Fuel

Calorific Mode of burning value (kcal)

Biogas (gobar gas) (m3) 4713 Kerosene (liter) 9122 Firewood (kg) 4708 Cowdung cake (kg) 2092 Charcoal (kg) 6930 Soft coke (kg) 6292 Butane (kg) 10882 Electricity (kWh) 860 Source: Brown et al. (2011)

In standard burner Pressure stove 10 open chulha -do-do-doIn standard burner Hot plate

Mode of efficiency (%)

Effective Heat (kcal)

60 50 17.3 11 28 28 60 70

2828 4561 814 230 1940 1762 6529 602

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Fig. 5.2 Uses and Equivalents of Biogas Source: Klass (1998), Wierzbicki (2012)

5.11.4. The Basic Theory of Biogas Production The fermentation process is a complicated one involving two main stages: Stage 1: Bacteria break down complex organic materials, such as carbohydrate and chain molecules, fruit acid material, protein and fats. The disintegration produces acetic acid, lactic acid, propanoic acid, butanoic acid, methanol, ethanol and butanol as well as carbon dioxide, hydrogen, H2S and other non-organic materials. In this stage the chief micro-organisms are the ones that break down polymers, fats, proteins and fruit acids, and the main action is the butanoic fermentation of polymers. Stage 2: The simple organic materials and CO2 that have been produced are either oxidized or reduced to methane by micro-organisms, the chief ones being the methane producing or methanogenic micro-organisms of which there are many varieties. These need a supply of nitrogen. This stage may be represented by the following overall reaction, i.e. Equation 5.2: ' %(5 ") 6

+ 7%# " 89:; 0/8?;7 ;@ A>8907> B0/8>:?0 → 37 %* + 37 "# + %>08

Equation 5.2 – Fermentation Process Individual reactions include: (i) Acid break down into methane

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2 & %C ""% + 2%# " →

%* + 3 "#

(ii) Oxidation of ethanol by C02 to produce methane and acetic acid 2 %& %# "% + "# → 2 %& ""% + 2%# " (iii) Reduction with hydrogen of carbon dioxide to produce methane "# + 4 %# →

%* + 2%# "

Thus, complex organic materials are broken down through the action of microorganisms to produce simple organic acids, alcohols, carbon dioxide etc., which are then oxidized by micro-organisms to produce methane. This is a complex biological and chemical process and a balance must be maintained between the two stages. If the first stage proceeds at a much higher rate than the second stage, acids will accumulate and inhibit the fermentation in the second stage, slow it down and stop it. According to Klass (1998), the biodegradability can be predicted based on substrate composition by the following model, i.e. Equation 5.3: B = 0.830 - 0.028 X Equation 5.3 – Biodegradation Predictability where, B = Biodegradable fraction of volatile solids (%) X = VS lignin determined by 72% Sulphuric method (%) The model is based on the concept that lignin controls the extent of substrate biodegradation. The general order of decreasing anaerobic biodegradability is monosaccharides, hemicellulose, cellulose, protein and lignin. One of the ways of increasing methane yield in an anaerobic digestion process is to pretreat the feed so that the complex organic structures, especially the polymers, are broken down to lower molecular weight species which then become more susceptible to microbial degradation. For example, acid hydrolysis of cellulose affords glucose which has good biodegradability. Alkaline treatment can be used to break lignocellulose complexes to make the degradable components more accessible to attack.

5.12. Necessary Conditions for Biogas Production Since fermentation is the result of the action of many kinds of anaerobic microorganisms, the better the living environment of these micro-organisms, the faster the production of biogas (Farooq et al., 2012). If proper conditions cannot be maintained biogas production will slow down or cease altogether. Optimum living conditions for these micro-organisms are given in the following paragraphs.

5.12.1. Temperature The temperature for fermentation in the pit will greatly affect the production of biogas. Under suitable temperature conditions the micro-organisms become more active and gas is produced at a high rate. Methane can be produced within a wide

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range of temperatures; depending on prevailing conditions three types of fermentations are possible at high, medium and ordinary temperatures. For high temperature fermentation, the temperature should be 50°C – 55 °C, for medium 30°C – 35 °C and for ordinary 10°C – 30 °C. The process of digestion and gasification proceeds at the highest rate when the temperature is around 30 oC. At lower temperature digestion is retarded and below 15 °C it is reduced so much that the gas plant produces very little gas. Methane micro-organisms are very sensitive to temperature changes. A sudden change exceeding 3 °C will affect the production. Therefore, one must ensure relative stability of temperature.

5.12.2. Air Tightness None of the biological activities of anaerobic micro-organisms, including their development, breeding and metabolism requires oxygen. In fact, they are very sensitive to the presence of oxygen. The breakdown of organic materials in the presence of oxygen will produce carbon dioxide; in airless conditions, it will produce methane. If the biogas pit is not sealed airtight the action of the micro-organisms and the production of biogas will be inhibited and some gas will escape. It is therefore crucial that the biogas pit be water-tight and air-tight.

5.12.3. Water Content There must be suitable water content as the micro-organism’s excretive and other metabolic processes require water. The water content should normally be around 90% of the weight of the total contents. Both too much and too little water is harmful. With too much water the rate of production per unit volume in the pit will fall, preventing optimum use of the pit. If the water content is too low, acetic acids will accumulate, inhibiting the fermentation process and hence production; a rather thick scum will form on the surface. The water content should differ according to the difference in raw material for fermentation.

5.12.4. Detention Period The detention period is the time for which fermentable material resides inside the digester. In KYIC design this period is about 55 days. Ordinarily maximum gas production takes place within the first 4 weeks and then it tapers off gradually; 45 to 55 days is optimum. Thereafter, the production is so small in quantity that it is not worthwhile making larger investment on a bigger digester. If the size of the digester is made smaller, the outgoing slurry comes out imperfectly digested and is likely to attract flies to give odour. The same may happen if the digester is loaded more than its rated capacity. The detention period could be considerably reduced if the optimum temperature could be maintained or contents of the digester are augmented. For a very broad idea some figures given by some research workers on the rate of gas production per week may be of interest, shown in Table 5.11:

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Table 5.11 Rate of Biogas Production per week basis in a Digester Time Span

Rate of biogas Production (%)

1st Week

37.0

2nd Week

26.5

rd

17.5

th

10.0

th

5.75

th

3.25

3 Week 4 Week 5 Week 6 Week Source: (Klass, 1998)

5.12.5. Necessary Nutrients There should be plentiful material for the normal growth of the micro-organism. They must be able to extract plentiful nutrients from the source of fermentation. The main nutrients are carbon, nitrogen and inorganic salts. A specific ratio of carbon to nitrogen must be maintained between 20:1 and 25:1. This ratio will vary for different raw materials, and sometimes even for the same ones. The main source of nitrogen is human and animal excrements, and of carbon polymers in crop stalks. To maintain a proper ratio of carbon to nitrogen, there must be proper mixing of the human and animal excrements with polymer sources.

5.12.6. Maintaining Suitable pH Balance pH denotes acidity and alkalinity of a substrate. The micro-organisms require a neutral or a mildly alkaline environment. A too acidic or too alkaline environment will be detrimental. A pH between 7 and 8.5 is the best for fermentation and normal gas production. The pH value for a fermentation pit depends on the ratio of acidity and alkalinity and the carbon dioxide content in the pit, the determining factor being the density of the acids. When excessive loading is resorted to, the acid-forming bacteria are far more active than the methane-forming bacteria resulting in lowering the pH. For the normal process of fermentation, the concentration of volatile acids measured by acetic acid should be below 2,000 parts per million; too high a concentration will greatly inhibit the action of the methanogenic micro-organisms.

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5.12.7. Harmful Materials The micro-organisms that make the biogas are easily affected by many harmful materials which interfere with their livelihood (Huber et al., 2006). Maximum allowable concentrations of such harmful materials are as follows in Table 5.12: Table 5.12 Maximum tolerable concentration of harmful material to the Biogas producing Microorganism Harmful material

Maximum allowable concentration

Sulphate (SO4)

5,000 ppm

Sodium chloride (NaCl)

40,000 ppm

Copper (Cu)

100 mg l-1

Chromium (Cr)

200 mg l-1

Nickel (Ni)

200-250 mg l-1

Cyanide (CN)

below 25 mg l-1

ABS (detergent compound)

20-40 ppm

Ammonia (NH3)

1,500-3000 mg l-1

Sodium (Na)

3,500-5500 mg l-1

Potassium (K)

2,500-4500 mg l-1

Calcium (Ca)

2,500-4500 mg l-1

Magnesium (Mg)

1,000-1500 mg l-1

Source: (Huber et al., 2006)

They must either not be presented or their concentration must be diluted, for example by the addition of water.

5.13. Biogas Plant A biogas plant is a pit constructed in a way that combustible gas is formed when fed with human, animal and vegetative wastes through fermentation. The gas plants have three main parts: a digester, a gas holder and gas main with distribution system. Depending on the amount of raw material to be handled, the digester may be of either single chamber or double chamber type. The size of the gas holder should be such as to accommodate the volume of gas to be consumed during the day with sufficient margin for next day.

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There are different ways and possibility of constructing a biogas plant. Basically biogas plants are of two types, viz. movable gas holder type and fixed dome type.

5.13.1. Movable Gas Holder Type It is a continuous operation plant, i.e. as the material to be fermented is charged into fermentation tank, the same volume of the fermented material overflows out of it. Continuous systems are simple to operate, have a high gas yield and need a relatively small pit. At places where it is easy to excavate to a depth of 5 to 6.5 m, vertical gas plants are constructed, Where the water table is high and it is difficult to excavate deep pits due to rocky strata, horizontal type of gas plant of shallow depth are constructed. Two slanting asbestos cement pipes are connected to the digester near its bottom on either side of the partition wall and have their opening on the surface to the ground by the side of the top of the wall. The floor level of the mixing tank is given slope opposite to the direction of inlet pipe to prevent inorganic solid particles from entering digester, which may silt it. In gas plants, having more than 1.60 m diameter, a partition wall is provided to divide the digester into two chambers which will serve as primary and secondary digestion chambers and also prevent channeling of the slurry through the digester. The ripe slurry will be taken out from the bottom of the secondary digestion chamber. This is achieved by operating the discharge pipe 7.5 cm below the digester top. A ledge is built into the digester at a depth equal to that of the gas holder. It prevents the gas holder from going down when no gas is left in it, thus preventing the slurry from entering gas pipe. Its most important use is to guide all gas bubbles from the digester into the gas holder. The gas holder is a drum-like structure constructed of mild steel sheets. It is guided by a central guide pipe erected in the center of the digester. A pipe is fitted in the gas holder at its center which engages the guide keeping the gas holder in position and yet free to move up and down. The gas holder also has a rotary movement which is used to break up the mat formed on the surface of slurry in the digester (Demirel and Scherer, 2011). The biogas plant which is largely in use mainly consists of digester and gas holder (Figure 5.4, Figure 5.4). Digesters are constructed below the ground level. 5.13.1.1. Design of Biogas Plant The size and design of the plant will depend on raw material available for digestion, quantity of gas required, capital available for investment, climatic conditions, and soil conditions and water table.

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Fig. 5.3 Details of Digester for KVIC Design (Plant Capacity 6 cubic meter) Source: Consulted (Raju et al., 1991; Nagamani and Ramasamy, 1999; Demirel and Scherer, 2011)

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Fig. 5.4 Details of Gas Holder for KVIC Design (Plant Capacity: 6 cubic meter) Source: Consulted (Raju et al., 1991; Nagamani and Ramasamy, 1999; Demirel and Scherer, 2011)

The basic parameters adopted for designing gas plant for different capacities are as under: (i) Estimated production of gas per kilogram of fresh cattle dung has been assumed as 0.036 m3;

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(ii) The dilution ratio of the media is 7 to 8 % solid matter, i.e. 1:1 to 1:1.25 proportion of cattle dung and water by volume; (iii) Retention period is 30 to 50 days for different organic wastes and climatic conditions; (iv) The delivery pressure is 10 cm water column; (v) Gas consumption is assumed to be 0.24 m3 per day per person. The above-mentioned criteria are to be considered for designing plants of different capacities. The design procedure of a medium size plant of 6 m3/day capacity is given as follows: Fresh cattle dung required

6 = 1.66,66 .= 0.036

The same quantity of water is mixed with cattle dung. Therefore, the total quantity of cattle dung slurry after mixing equal quantity of water comes to 333.332 kg and density for the same is 1089.36 kgm-3. Hence total volume of raw material added/day =

&&&.&&# (5UV.&'

= 0.30599 m#

Considering retention period as 50 days, volume of digester comes to 50 x 0.30599= 15.3 m3 Therefore, to produce 6 m3 gas per day, the volume of digester required will thus be 15.3 m3, i.e. we can assume that to produce one cubic meter of gas the volume of digester will be 2.5 m3. This can be taken as the basis for working out the volume of the digester for any size of gas plant. This volume must be net usable volume excluding space occupied by partition wall and the upper empty tolerance. Hence, for practical purposes, the digester dimensions must come to 2.75 times the volume of gas produced per day. The dimension of the digester can be achieved by fixing the depth initially. It was observed at that the digesters having depth of 4 to 6 m are very suitable for maintaining the digester temperature irrespective of atmospheric temperature. This will be very necessary for the colder regions. Accordingly, 4 to 6 m depth has been taken for the gas plants of capacity 2 to 25 m3 gas per day. By taking depth of the digester as 4.27 m for 6 m3 gas plant the diameter of the well comes to 2.2 m. 5.13.1.2. Gas Holder Design Normally the gas holders are designed considering distribution of the gas during day and night to arrive at storage capacity. For a 6 m3 per day requirement the storage capacity of the gas holder is kept at 3.5 m3 of which 3 m3 can be delivered for use. This is done on the basis that the gas collected overnight will be consumed in the morning for breakfast and cooking, and the day's production collected in the gas holder will be used for preparation of dinner etc. The hours of use of gas should be noted so that the storage capacity can be accordingly adjusted. For example, in case of school and laboratories gas will be used only in the day time, i.e. they may require gas for seven to eight hours continuously.

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The weight of the gas holder is designed to give a pressure of about 10 cm water column, i.e. 100 kgm-2 of the circular area of the holder. The total weight will be adjusted taking the weight of angles, M.S. sheets and weight of the central pipe fitted in the gas holder. 5.13.1.3. Operation of the Plant Fresh dung mixed thoroughly with an equal volume of water is fed in the fermentation tank through the feeding pipe till the level of the slurry reaches that of the outlet channel for the fermented slurry. Grass and other floating materials present in slurry should be removed or chopped to 1.25 to 2.5 cm pieces; otherwise they may choke the pipe and float on the surface of slurry to form a thick layer of mat. As the gas evolves the gas holder rises. After about three weeks, the initially accumulated gas is released into the atmosphere as it contains considerable amount of carbon dioxide and does not burn efficiently. After another week, there will be sufficient gas in the gas holder for direct use. After the gas has first formed, production is maintained by daily feeding of fresh dung after mixing with equal volume of water. The quantity of dung depends on the capacity of the plant. Simultaneously with the gas production, the spent slurry will overflow into the outlet chamber from where it can be led either directly into compost pit or into a shallow chamber where it may be sun-dried. Occasionally the gas holder should be rotated to break the scum that forms in the digester. 5.13.1.4. Ferrocement Gas Holder Ferrocement is a composite material consisting of layers of thin wire mesh impregnated with rich cement mortar. It has high resistance to cracking and permeability which is essential for the satisfactory functioning of gas holder. Ferrocement can be cast into sections as thin as 1 cm. It is suited for precast products because of the resulting low weight of the components. Ferrocement gas holders are much cheaper than mild steel gas holders of the same capacity. They can be fabricated in the rural areas using local labour, skilled and unskilled. The material has low thermal conductivity and therefore the rate of gas production is uniform in all seasons. It has high resistance to corrosion and needs minimum maintenance. Ferrocement has high impact strength and can withstand the rigors of transport and handling. Any accidental damages caused can be easily repaired. Ferrocement gas holder consists of a wall unit and a roof unit, cast separately and assembled. The reinforcement for the wall unit consists of two layers of galvanized iron woven wire mesh and one layer of mild steel-welded wire fabric in between. The welded wire fabric gives the necessary strength and rigidity to the wall unit while the woven mesh constitutes the skin reinforcement which ensures crack control. The bottom edge from any of the wall unit is reinforced by a ring made of mild steel angle which protects the edge from any damage during handling. Inserts are provided near the top and bottom edges for attaching the scum-breaking arrangement. The roof unit of the gas holder is a spherical dome. This shape is very efficient for resisting the forces due to self-weight and internal pressure. It depends upon masonry moulds or wooden moulds. The mild steel rings may be replaced by rings of

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galvanized iron wire to keep the thickness of dome within desired limit. The dome is provided with six fillets equally spaced along the periphery for laterally supporting the wheels of the guides. A socket is placed on the surface of the dome for connecting the gas outlet pipe. The wall and the roof unit are cast side by side and when these have attained sufficient strength (usually after seven days) the roof unit is supported over several props in alignment with the wall unit. Mortar is applied on the junction from the inside as well as from the outside. The curing is continued for another seven days after which the mortar attains sufficient strength. The mortar used for the gas holder consists of ordinary Portland cement and coarse sand in the proportion of 1:2 with a water/cement ratio of 0.45. The mix has a stiff consistency to facilitate application by hand on a curved surface. The scum-breaking arrangement is attached to the inserts provided near the top and bottom edges of the wall unit. It consists of three mild steel bars at top and bottom placed radially and connected by vertical bars. The scum formed on the surface of the slurry is broken by vertical bars on rotation of the gas holder once in a few days. As the cement mortar is porous it is therefore not fully impermeable to gas. It is necessary to apply suitable surface coating to the inside and outside surfaces of the gas holder to improve its impermeability to gas. In addition, these coatings provide protection against corrosion. Trials using bituminous surface coatings have given satisfactory results.

5.13.2. Fixed Dome Biogas Plant The fixed dome type biogas plants are widely prevalent in China. These plants are simple in construction; locally available materials and skill can be used. The cost is much lower than the existing plants of the conventional type. The distinctive feature of this design is that the gas-holder and digester are combined in one unit. There are no moving parts in this design. Wear and tear and maintenance are kept at a minimum. The whole plant is an underground dome, made of cement and bricks, enamel painted from the inside with a sloping masonry inlet and rectangular plastered outlet. The crown of the dome has an opening which is provided with a cement concrete disc cover sealed from all sides and held in position by its own weight. 5.13.2.1. Principles of Gas Storage When anaerobic digestion of organic residue occurs, the biogas produced goes up into the gas dome. As the biogas pressure increases, the digested liquid effluent is forced into the high position tank through the outlet. Biogas pressure is determined by the head of liquid between the liquid levels in the digesting chamber and in the high position tank. This may be shown by the relationship, i.e. Equation 5.4. P = γ∆h

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Equation 5.4 – Biogas Pressure Determination where, P = pressure of biogas (gcm-2)

γ = density of digesting liquid (gcm-3) ∆h = head of liquid between liquid levels in the digesting chamber and in the high position tank (cm) When biogas is to be used, the outlet value is opened and the liquid in the high position tank moves back into the digesting chamber, thus forcing biogas out through the outlet pipe. The exhaustion of gas may be until the liquid levels inside and outside the digesting chamber are equal. Although at this equilibrium condition the gas dome is still filled with biogas above the liquid level, this biogas is not available for immediate use until additional gas generation raises the pressure of liquid head (∆h). 5.13.2.2. Parts of Fixed Dome Biogas Plant This is where the materials to be fermented enter the fermentation compartment. This inlet should be large enough to allow easy introduction of materials. It is normally a slanting tube or trough. The lower end should open into the fermentation compartment at about mid-height. The inlet should also be linked to the excreta troughs of toilets and pigsties. The inlet should incline enough to ensure the natural flow of these materials into the fermentation compartment. This is where the residue from the fermentation process is extracted. Its size should depend on the volume of the pit. There should be an adequate distance between inlet and outlet to prevent freshly incoming materials going into the outlet. To avoid clogging by sludge, the inlet and the outlet should not be set too low, and to prevent biogas going out of the gas dome, they should not be set too high. In the rectangular pit this separation wall creates a gas storage tank. For the round pit, the separation wall is the wall above the mouths of the inlet and outlet. The depth of the wall is normally calculated downwards from the top of the tank, so that it comes to about half the total depth of the pit (Figures 5.5, 5.6). If the separation wall is built too low it will impede air circulation, and pose a danger of suffocation for the people who clear and maintain the pit. If the separation wall is too high, it diminishes the gas storing capacity of the tank, especially at times when fertilizer is needed. If one extracts a little too much fertilizer and the liquid contents fall below the separation wall, this will cause gas to escape from the tank.

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Fig. 5.5 Diagram of a Circular Biogas Pit Source: Jamil and Jamil (2009)

Fig. 5.6 Diagram of a Rectangular Biogas Pit Source: Jamil and Jamil (2009)

(a) Fermentation Compartment and Gas Storage Tank These two sections are one entity. They connect the inlet and outlet, and form the area where the gas is produced and stored. The middle and lower sections are the fermentation compartment, the upper is the gas storage tank, with the cover above it. When the fermentation material is let into the fermentation compartment, gas is produced through the action of micro-organisms and fermentation break-down. The gas rises to the upper section and into the gas storage tank. This compartment and the tank are the principal sections of the pit, and should be strictly sealed to be completely water - and air - tight. The size of the digester is determined by temperature of digesting content, the operation and feed stocks. Usually 0.8 to 1.5 m3 of digesting chamber per person is suitable.

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Water Pressure Tank The water pressure tank is built above the gas storage tank, with the cover to the pit forming both the ceiling of the gas tank and the bottom of the water tank. Around the perimeter of the cover, a ridge about 40 cm high should be built, with a hole 5 cm in diameter going through it just above the inlet. As the gas rises into the gas storage tank, the liquid below it is pressed down. This raises the level of the liquid in the outlet. When it surpasses the height of the cover, the liquid flows through the hole into the water pressure tank. When the gas pressure decreases, it flows back out of the water tank into the pit. As the gas is being produced, the liquid level rises. When the gas is being consumed, the liquid level falls. Thus, by the automatic changes in the water pressure above, the gas within the tank will be maintained at a constant pressure. The gas outlet pipe is set into the gas tank cover. At the bottom, it opens into the gas storage tank in level with the bottom of the cover. At the upper end, it may be connected to a plastic or rubber hose tubing to pipe the gas to carry it to the place of use. The mixer is normally made of wooden sticks. It is used to stir the fermenting liquid and to break through the crust or scum formed on the surface of the liquid, to let the gas come through normally. Breaking of scum facilitates adequate contact of bacteria with substrate and unanimous temperature of the upper and lower portions of the digesting content. Piston shaped stirrer may also be used. This stirrer is a round plank with diameter a little smaller than that of the inlet opening, fixed to one end of a long bamboo pole with four steel wires between the edges of the plank and the pole. Back and forth movement of the stirrer inserted into the inlet pipe will violently turn the content in the digester over and over. The piston stirrer may be used also in feeding. It is not necessary to fix a mixer into small pits built for individual family. Two main shapes namely round and rectangular are used in Republic of China (Rajendran et al., 2012). Cylindrical digesting chamber is preferred over rectangular one, because in the structure of latter, bending stress is created by the soil pressure while the chamber is empty. In regions where stone is available, it is convenient to build a circular pit out of stone slabs (flat stones having one dimension much smaller than the other two, forming thin slabs that can be used for surfacing, Figure 5.7) or stone of irregular shape or rectangular pit out of stone slabs. In plains or riverbed regions, rectangular and circular pits can be built out of triple concrete, rectangular pits can alternatively be built with egg stones (flattish stones taken from riverbeds, roughly egg-shaped and about 50 cm in diameter). A spherical pit built with stone slabs will require about 40% less work and material than a rectangular pit built with oblong stones and having the same volume (Smith, 2013). Triple concrete is a traditional Chinese building material. It is normally made from lime, sand (which may contain small stones or pebbles) and clay or lime, crushed clinkers and clay mixed in specific proportions with water (Jiang et al., 2011). A spherical shape allows a large internal volume and a small opening, which facilitates sealing to prevent air-and water leakage. This shape also produces an even pressure on all sides. Converting old manure pits or vegetable stores into biogas pits

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is another popular and economical method. As far as possible local material should be used in the construction depending upon the conditions.

Fig. 5.7 Design of a Circular Pit made from Stone Slabs Source: Smith (2013)

5.14. Shortcomings of Water Pressure Digesters Since a part of the digesting liquid is forced into the high position tank while generating gas, this part of the liquid is outside the gas collection chamber and gas produced from that part of the liquid is lost. The possibility of the escape of ammonia nitrogen contained in the digesting liquid within the high position tank is increased. The odours in the vicinity may be objectionable. While gas is being generated, there is a notable hydraulic head between the liquid levels in the digesting chamber and in the high position tank, and thus the inner surface of the digesting chamber bears a considerable outward stress. Therefore, the digester must be solidly constructed, the land fill around the chamber must be compact, and the soil covering the top must be thick enough to avoid the hazard of system collapse. As the gas pressure increases, the possibility of gas leakage arises. The blockage may occur when the sludge concentration of the content is too high.

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5.15. Advantages of Biogas Plant (i) Common materials may be used in the construction. (ii) Large quantities of steel and iron are not required. (iii) The construction is simple. (iv) The plant does not have any movable part. (v) The plants are durable if construction quality is proper.

5.16. Operation of the Biogas Plant There are two feeding systems: batch type feeding system and semi-continual feeding system. Though batch feeding system is simple, the starting of plant is difficult. The generation of scum is more and there is uneven and low production rate of gas. However, semi-continual system is better. In this, feeding is done once or twice daily. Sufficient digested sludge must be added for seeding during starting period. The amount of seeding should not be less than 20% of the volume of the digesting content.

5.17. Cleaning of the Plant Scum and precipitate would accumulate in the digesting chamber after the operation for a certain period. This reduces effective volume of content and hinders gas production. Therefore, cleaning is essential. Cleaning of the plants can be done by batch-wise cleaning or by semi-continual cleaning.

5.17.1. In Batch-wise Cleaning All the scum and part of the precipitate are taken out of the digesting chamber every time while the remainder of the precipitate serves as feed sludge for restarting. No routine cleaning is needed between two intermittent cleanings. The cleaning labour, prolongs operation and brings about difficulties in restarting. Persons often have to enter the digester, it is neither clean nor safe for them.

5.17.2. In Semi-continual Cleaning The digesting chamber has a large outlet which allows cleaning tools to reach the digester. Precipitate is to be removed at seven to ten days interval. This process hinders neither gas production nor operation. The plug of the digesting chamber may be removed after a long period to remove the scum. Persons need not enter the digester and operation resumes immediately after cleaning.

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5.18. Chinese Biogas Appliances Chinese biogas burners for cooking and lighting are usually made of fired clay. Although their combustion efficiency is not high (less than 40%) their cost is low. Indian burners with a combustion efficiency of about 60% are made from cast iron with gunmental injectors and are costly (Smith, 2013). Recently Chinese burners are being made more efficient and Indians are developing low cost but efficient porcelain burners.

5.19. Biogas for Mechanical Power In running diesel engine, it is necessary to feed 15 to 20% diesel along with gas and in the situation the consumption of the gas is about 0.42 to 0.50 m3 per bhphr-1. In petrol engine, however, it is not necessary to burn petrol as it can run entirely on gobar gas. In both the cases the starting must be done either by diesel or petrol. Unless, one has very large size gas plant, i.e. of a capacity not less than 20 m3, it is not advisable to attach an engine. The latest research results show that advancing of injection timing by 30° BTDC gave best results for biogas-diesel operation of engine. The engine developed 82% of the maximum bhp on dual-fuel with 70% diesel replacement and 0.813 m3 per bhphr-1 biogas consumption rate. The cost of operation of engine was 24% lower with dual-fuel as compared to pure diesel operation.

References Bernet, N., and Béline, F. (2009). Challenges and innovations on biological treatment of livestock effluents. Bioresource Technol., 100, 5431-5436. Bernal, M. P., Alburquerque, J. A., and Moral, R. (2009). Composting of animal manures and chemical criteria for compost maturity assessment. A review. Bioresource Technol., 100, 5444-5453. Brown, M. L., Bulpitt, W. S., Walsh Jr, J. L., and McGowan, T. F. (2011). Biomass and Alternate Fuel Systems: An Engineering and Economic Guide. John Wiley and Sons. Hobken, New Jersey, Canada. Chandra, R., Takeuchi, H., and Hasegawa, T. (2012). Methane production from lignocellulosic agricultural crop wastes: A review in context to second generation of biofuel production. Renew. Sustain. Energy Rev., 16, 1462-1476. Chaudhry, M. A., Raza, R., and Hayat, S. A. (2009). Renewable energy technologies in Pakistan: prospects and challenges. Renew. Sustain. Energy Rev., 13, 16571662. De La Fuente, C., Alburquerque, J. A., Clemente, R., and Bernal, M. P. (2013). Soil C and N mineralisation and agricultural value of the products of an anaerobic digestion system. Biol. Fert. Soils, 49, 313-322. Demirel, B., and Scherer, P. (2011). Trace element requirements of agricultural biogas digesters during biological conversion of renewable biomass to methane. Biomass Bioenergy, 35, 992-998.

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Farooq, M., Chaudhry, I. A., Hussain, S., Ramzan, N., and Ahmed, M. (2012). Biogas up gradation for power generation applications in Pakistan. J. Qual. Technol. Manage., 8, 107-118. Huber, G. W., Iborra, S., and Corma, A. (2006). Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. Chem. Rev., 106, 40444098. Jamil, A., and Jamil, M. E. (2009). The essence of dead cattle organs in producing biogas–a sustainable solution to the energy problem in rural areas in Bangladesh and other developing countries. WIT Transac. Ecol. Environ., 120, 759-769. Jayathilakan, K., Sultana, K., Radhakrishna, K., and Bawa, A. S. (2012). Utilization of byproducts and waste materials from meat, poultry and fish processing industries: a review. J. Food Sci. Technol., 49, 278-293. Jiang, X., Sommer, S. G., and Christensen, K. V. (2011). A review of the biogas industry in China. Energy Policy, 39, 6073-6081. Klass, D. L. (1998). Biomass for renewable energy, fuels, and chemicals. Academic press, San Diego, CA, USA. Møller, H.B., Sommer, S.G., and Ahring, B.K. (2002). Separation efficiency and particle size distribution in relation to manure type and storage conditions. Bioresource Technol., 85, 189-196. Moreki, J. C., and Keaikitse, T. (2013). Poultry waste management practices in selected poultry operations around Gaborone, Botswana. Int. J. Curr. Microbiol. App. Sci., 2, 240-248. Nagamani, B., and Ramasamy, K. (1999). Biogas production technology: an Indian perspective. Curr. Sci., 77, 44-55. Oenema, O., Oudendag, D., and Velthof, G. L. (2007). Nutrient losses from manure management in the European Union. Livestock Sci., 112, 261-272. Rajendran, K., Aslanzadeh, S., and Taherzadeh, M.J. (2012). Household biogas digesters—A review. Energies, 5, 2911-2942. Raju, N. R., Devi, S. S., and Nand, K. (1991). Influence of trace elements on biogas production from mango processing waste in 1.5 m3 KVIC digesters. Biotechnol. Lett., 13, 461-464. Smith, K. (2013). Biofuels, Air Pollution, and Health: A Global Review. Springer, Plenum Press, New York, USA. Wierzbicki, S. (2012). Biogas as a fuel for diesel engines. J. KONES, 19, 477-482.

Chapter 6

Animal By-products Generated in Rural Areas Faizan ul Haq Khan, Abdul Nasir Awan and Shafique Anwar*

Abstract Meat industry in the Pakistan has made its place on national and international level. On one hand Animal produces meat which is the biggest source of nutrients and energy for human beings and on other hand it produces byproducts which has great economic potentials for the meat industry of Pakistan. Although it has received very little attention, yet a lot of work should be done in this area by raising suitable breeds of livestock to enhance the quality of meat. Due to non-hygienic conditions prevailing in the slaughter house most of the animal byproducts did not give positive returns to the meat industry. The economic loss due to non-utilization and underutilization of carcass and defective flaying cost out to be Rs.5 billion per annum. The animal byproducts can be placed into two groups, for example, edible and non-edible. Different methods of processing are carried out to yield products of economic importance, beside their sanitary disposal. In this chapter, efficient utility of different byproducts either edible or non-edible has been discussed in detail. Keywordss: Animal byproducts, processing of byproduct, processing of carcass, rendering process, utilization,

6.1.

Introduction

Basically, the term 'byproduct' is used to denote every part or particle of value, except dressed meat produced from any part of meat animal. Meat industry in Pakistan has *

Faizan ul Haq Khan˧, Abdul Nasir Awan and Shafique Anwar Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

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great economic potentialities but so far it has received very little attention. The quantity of meat produced is far below the requirements and suitable meat breeds of livestock have not yet been developed. The hygienic conditions in most of the slaughterhouses are appalling and animal byproducts of substantial value are wasted. In villages, the situation is still worse. The dead animals are flayed by the poorer sections of the community who are financially weak and have no means to utilize the fallen animals in a scientific manner. The economic loss due to non-utilization and under-utilization of carcass and defective flaying etc. has been estimated at about 50 billion rupees per annum (Zia et al., 2011). Hides and about 60% of the bones of cattle, buffaloes and other big animals are collected. The rest of the byproducts, viz. meat, fat, horns and hoofs, can go waste. The flesh is eaten away by the birds and scattered causing nuisance. From economic and sanitary point of view, it is essential to make use of all the byproducts by converting them into products of extensive and valuable range. Table 6.1 Approximate Material Balance of Meat and Byproducts from Large Animals Organs Meat (boneless) Bone, head and feet Fat Head, meat and brain Tongue Liver Heart Lungs Spleen Stomach Blood Hide Other offals (genital udder, tail-end etc.) Paunch content and waste Casings Kidneys Urine, body fluid, bile, dung etc. Shrink 2.5% of live weight Unaccounted

Live weight (kg) 100.00 80.00 6.00 1.00 1.00 5.00 1.50 7.00 1.00 2.50 11.00 26.50 14.00 56.00 7.00 0.50 10.00 34000.00 8.75 1.25 350.00

Source: Coutand et al. (2008)

The animal byproducts fall into two groups, viz. the edible and non-edible. The edible ones include tallow, lard, guts, glands, tail stumps and blood. The non-edible ones include hides and skins, wool, hair, bones, meat wastes, horns and hoofs. Of the various byproducts, the important ones are hides and skins, hair, bristles, bones,

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horns, and hoofs and blood. The approximate material balance of meat and byproducts from large animals is shown in Table 6.1.

6.2.

Processing of Carcass and Slaughterhouse Waste

Carcass and slaughterhouse wastes are processed to yield products of economic importance, besides their sanitary disposal. The products that can be obtained are stock feed (meat meal, meat- cum-bone meal, and bone meal), fat and fertilizer. Main requirements of processing are: (a) Sterilizing and making the product safe for use as stock feed; (b) Reducing the moisture to a minimum to prevent spoilage and economizing on transport; (c) Recovering the fat from meal which would otherwise cause rancidity.

6.3.

Methods of processing

6.3.1. Simple Method of Cooking and Drying When the waste material available is in small quantity and establishment of modern processing equipment is not economical, this method can be utilized. Boiling of the material can be undertaken in an open vessel or in an oil drum. Boiling is continued for two to four hours. Fat is separated from the liquid and the cooked material is compressed to remove as much water and fat as possible and is dried in sun or in heated trays. The dried meal is powdered and kept in bags (Jayathilakan et al., 2012). Even though this method is primitive and cannot be used for all types of raw waste material, still it is good to utilize the carcasses rather than throwing them as waste.

6.3.2. Wet Rendering When the raw material is processed with added water or condensate derived from steam, it is called wet rendering. The wet-rendering tank is usually a vertically cylindrical one with a cone shaped bottom and a gate valve outlet of 20-30 cm diameter. On the top of the tank is a man-hole through which obnoxious gases escape without reducing the pressure. Higher the pressure, quicker will be the disintegration. For this reason, in large plants pressure is maintained at 4 kgcm-2. However, such high pressure may deteriorate the quality of the fat. For this reason, a pressure of 2.7 kgcm-2 is usually applied. The time required to disintegrate the tissue and free fat varies from five to eight hours, depending on the character of the offal, Blood should not be put into the tank until the fat has been drawn off, as blood gives the fat a dark colour. After cooking is completed, the contents of the tank can settle for about two hours. Then the water and fat are drawn off through the side cocks. After the removal of water and grease, the digested mass of meat and bone is taken out. At this stage the slush may contain up to 55% moisture and about 15% fat. A press is used to further reduce the moisture and fat content. The material is further dried in a dryer for reducing the moisture content to less than 8%. Wet rendering is not recommended as it is a cumbersome process and losses of protein occur in the stick water.

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6.3.3. Dry Rendering The dry-renderer is a double-walled steam-jacketed horizontal tank fitted with agitators to keep the materials inside in continuous motion for uniform heating and to prevent charring. The material inside the renderer is dried by indirect heat from the steam applied to the jacket. The dry heat transmitted from the steam jacket to the raw material converts the moisture present in it into steam, which gradually builds up the internal pressure. This pressure combined with agitation, disintegrates the material and breaks down the fat cells. It is desirable that bones are broken into pieces and the meat and offal are reduced to 2 kg size pieces. The prepared material is fed into the renderer and steam pressure gradually raised. The drying process involves; (a) Heating the raw material to 125 °C, (b) Sterilizing the raw material at 125 °C for 15 minutes, and (c) Releasing the pressure and drying of the charge. At the end of the drying period, the material can settle and the discharge door opened. The fat and liquids are run off into a heated percolator below the drier door. With the agitator revolving, the solids fall out into the percolator. A puller is used to remove the last pieces. Large size bone pieces may be removed manually. The solid residues known as cracklings are then discharged from the percolator into a centrifuge to extract the remaining fat. Each charge in the centrifuge takes about 20 minutes depending on the material and the degree of fat extraction required. The solids are removed from centrifuge, allowed to cool and then ground in a pulverizer or grinder and then bagged for storage. The meal should not contain more than 8% moisture and 10% fat.

6.3.4. Bone Digestion For the preparation of bone meal, bones separated from the carcass as well as large pieces of bones separated from the rendered material are charged into the bone digester and processed at 4 kgcm-1 for three hours. At the end of digestion, pressure is released and the liquid with fat is drained out through the valve at the bottom of the digester. Then the bone mass is discharged from the bottom side outlet. Fat is collected from the drained liquid.

6.3.5. Fat Settling Tank It is a vertical tank with a cone-shaped bottom standing on three legs. There is a provision for heating the contents with steam by indirect heat. Fat collected from the percolator tank, centrifuge and bone digester is poured into the tank from top and allowed to settle after heating. Fat is drained out from side outlet while sludge is removed from bottom outlet.

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Utilization of Fallen Animals

In past, the failure to make use of the carcass of fallen animals was responsible for enormous wastage of otherwise useful materials. However, presently carcass utilization has gained much importance and the byproducts of fallen animals are being utilized to the maximum advantage. Figure 6.1, shows a flow diagram for processing of fallen animals.

Fig. 6.1 Flow Sheet for Processing of Fallen Animals Source: (Edström et al., 2003; Franke-Whittle and Insam, 2013)

6.5.

By-Products

6.5.1. Hides and Skins The term hide denotes the outer covering of large animals, such as cows, buffaloes, horses, camels, etc. whereas the term skin is applied to that of smaller animals, such as sheep, goats and calves. Raw hides and skins as such have limited applications. They are used mainly for the manufacture of leather.

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The estimated annual production of hides in the world is about six million tons, out of which Pakistan's share is 12%. The estimated annual production of skins in the world is 1.3 million tons, out of which Pakistan accounts for 7.4%. In Pakistan, hides are produced mainly from cattle and buffaloes. The hides of cows, bulls and calves are different from the hides of buffaloes. The hides of fallen animals are very often spoiled to such an extent that they cannot be converted into good-quality leather. The fallen animals are generally collected rather late and flaying is done with crude tools and implements. Steps are being taken by some of the state governments and non-official organizations such as Khadi and village industries commission for encouraging the proper utilization of fallen animals. Proper flaying includes opening the hides at the knee-joint of one of the front legs, running the slit in a direct line through the brisket up to the other knee-joint and separating the knee-joints down to the hoofs; the kneejoints and the hind legs are similarly treated. The third and last slit is made from the rectum or the tail up to the neck, passing through the middle of the belly and the breast. Thereafter the sides of the carcass are raised up and then the tail and butt are skinned off. Finally, the back is flayed. Immediately after flaying the hide should be opened, allowed to cool and cleaned. Freshly flayed hides decay unless carefully preserved. The most important methods followed for curing are wet-salting, dry-salting and air-drying. About 80% of the hides obtained from the slaughtered animal are cured by wet-salting and the remaining 20% are air-dried. Fallen hides, which constitute more than 75% of the hides produced in Pakistan, are mostly dried on the ground (Moreki and Keaikitse, 2013). This is a defective method. It should be replaced with drying the hides on frames. In air-drying, the moisture content is reduced from 60% to 20 - 30%. In salted cure, the salt reduces the natural moisture content of the raw hide from about 60% to 40% and reduces bacterial activity . In dry-salted cure the hides are first wet-salted, piled and thereafter the moisture content is gradually reduced until dry. Curing with salt, soda and naphthalene yields good quality hides. The hides and skins are converted into leather and various utility items. Depending on the items to be produced there are variations in the techniques of processing raw hides and skins. Some of the commonly produced goods are footwears/shoes, garments, carryon items, travel requisites, sport goods, etc.

6.5.2. Fats The fats of animal origin may be of two types-the one directly entering the human dietetics long with fresh meats, organ meats and many processed meats, and the second denoting surplus fats being processed by various techniques into different edible and inedible products. While the fat obtained from slaughtered animals is used for edible purposes that recovered from fallen animals is mostly used for making inedible products like soaps, candles and grease. The fats that are stripped within the slaughter floor are termed as 'killing fats' and those dismembered in the meat cutting and processing rooms are termed 'cutting fats'.

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Raw fat should be handled hygienically, stored or passed on to the rendering department for processing into edible fat and cracklings. It must be heated to free it from the tissue by rupturing the cells and causing the fats to separate. The edible fat department must be separated from areas which handle inedible materials, and premises and equipment must be designed and maintained in the same manner as in any other area devoted to the processing of edible materials. Fat of good quality should have low free fatty acid (FFA) and water contents, good keeping quality, natural taste, flavour and colour, and high solidification point (Cunha et al., 2013). The quality of edible fat is largely dependent on the types of raw material employed, the storage time and temperature of the raw material before rendering and the type of rendering equipment used. The process of extraction of melted fat from the fatty tissues and condemned material is called 'rendering' and the process of cleaning the melted fat is known as 'clarifying'. The common methods of processing are described below. 6.5.2.1. Processing of Dead, Condemned and Other Inedible Offal and Recovery of Technical Fat The basic principles of this method are initial cooking (through dry rendering) with the objective of reducing the water content of the materials from 55 to 56%, liberation of fat from fatty tissues and sterilization of the product; followed by after-cooking defatting operations. The most common defatting technique practiced in many rendering plants, consists of percolation, centrifugal fat extraction and sedimentation. Advanced plants use continuous defatting techniques involving mechanical pressing or solvent extraction; some use charge-wise mechanical pressing or solvent extraction. Under conventional procedures it is possible to recover about 12.5% of the raw material as technical fat, with a meal yield of about 25% with a moisture content of 7% and 7 to 9% fat. It is possible to reduce the fat content in the meal up to 1% through solvent extraction procedures. 6.5.2.2. Processing of Clean Fat Trimmings and Edible Offals The raw materials are either cut into small cubes or are minced thoroughly before they are rendered into edible products. Either steam rendering or dry rendering procedure is followed. In steam rendering the fatty tissues are charged into a large tank with a conical bottom. Live steam is injected and the rendering takes place under pressure to hasten the time of cooking. The pressure is slowly released at the end of the cooking and the mass is settled before drawing off the tank water. In dry rendering the fatty tissues are charged into a horizontal, steam-jacketed cylinder, which has a set of blades rotating about a central axis and nearly touching the wall. Dry rendering is accomplished under elevated pressure, at atmospheric pressure, and sometimes under vacuum. When sufficient moisture has been cooked out and the fat released from the tissue, the mixture is dumped into strainers or filtered to remove the cracklings.

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Fig. 6.2 Utilization of Animal Fat Source: Lasekan (2013)

The rendered fats under both above procedures can be further treated by hydrogenation, bleaching, deodorization, inter-esterification, fractional crystallization etc., depending upon the facilities available and further uses of the rendered products. 6.5.2.3. Home Rendering or Open-Kettle Method The fatty material is chopped into small pieces and placed in a semi-circular metallic vessel, the size of which will vary depending upon the quantity of the raw material. Heat is applied from below by burning wood or other materials for varying lengths of time till the fat is well separated. Then the material is cooled and clear melted fat is decanted. People at home also adopt a similar procedure for preparing cooking oil from animal fats.

6.5.3. Bones Bones constitute an important livestock product. The bulk of the bones produced in Pakistan is from fallen animals. Bones consist of two main components, an organic framework and an infiltrate mass of inorganic salts. Fresh' bones contain 51%

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moisture, 15.7% fat, 11.4% ossein, and 21.9% mineral matter. Degreased bones contain 6% fat, 28% ossein, 56% calcium phosphate, 1% magnesium phosphate, 8% calcium carbonate and 10% calcium fluoride. A major portion of bones collected in Pakistan is utilized to produce crushed bones, bone sinews and crushed bone, and a small quantity is used for the manufacture of bone meals. In the process of preparing crushed bones and crushed bone meal is obtained as a byproduct. It is a very good source of phosphatic manure. 6.5.3.1. Bone Sinews Bone sinews are the fibrous and tendinous portions adhering to bones. Crushed bones are small pieces of bones less than 5.0 cm in length but not smaller than 4.8 mm. Crushed bones are of smaller size than 4.8 mm but more than 2.40 mm size. 6.5.3.2. Bone Meal Bone meal is obtained as a powder on crushing bones and can pass through 2.40 mm (3/32") mesh. This bone meal can be used as manure. The value of raw bone meal as manure depends on the degree of fineness to which it is ground. Sterilization of bone meal is carried out only when it is specifically needed for use in mineral mixtures that are meant for feeding poultry and livestock. The bone meal used as feed concentrate has following composition: 22.6% protein, 1.98% crude fiber, 25% calcium and 22.6% phosphorus. According to the Pakistani standard, the specification for bone meal as livestock feed is given in Table 6.2. Table 6.2 Bone Meal Specification as Livestock Feed Characteristic Moisture, per cent by weight, maximum (max.) Calcium, per cent by weight, minimum (min.) Phosphorus, per cent by weight, min. Crude fat, per cent by weight, max. Fluorine, per cent by weight, max. Acid-insoluble ash, per cent by weight, max. Spores of Bacillus anthracis, Clostridium botulinum, Clostridium chauvaei and Clostridium septicum

Requirement 7.00 32.00 15.00 1.00 0.06 1.00 Nil

Source: Mirzaei-Aghsaghali and Maheri-Sis (2008)

6.5.3.3. Phosphatic Bone Meal Phosphatic bone meal is obtained because of cooking and digesting the bone ill a bone digester under steam pressure. During the process of digestion, glue and tallow are extracted, digestion helps in the concentration of phosphate and in increasing citric acid solubility of the final product. 6.5.3.4. Bone Charcoal It is prepared by the dry distillation of bones in the absence of air in special retorts. The charcoal left over is crushed and graded. Bone charcoal is a valuable material

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used in sugar refineries. Bone oil (3-5%) also called Dippel oil, and ammonia (8%) are obtained during distillation. The former is used in polishing the nails. The carbon left over is used as shoe polish. The quality of different types of bone product is given in Table 6.3 Table 6.3 Quality of Different Types of Bone Products (percent) Quality Nitrogen P2 O 5 Citric acid Solubility

Bones (raw) 3 20 -

Bones (charred) Nil 36 -

Digested bone meal 2.4 27.4 23.8

Superphosphate (chemical fertilizers) Nil 17 (16 water soluble) -

Source: Coutand et al. (2008)

Tallow is obtained in a crude form from freshly chopped bones by treating them in a socket extractor. It is further refined for conversion to high grade tallow suitable for the soap and textile industries. The bones of the fallen animals can be better used for the manufacture of gelatin and glue which are the products of commercial importance. It is not easy to draw a line of demarcation between gelatin and glue. Broadly speaking, glue is impure, dark coloured or low test gelatin. Gelatin can be distinguished from glue by its purity, light colour, clearness and high jelly strength. Gelatin is further subdivided into two classes, viz. edible and technical. Edible gelatin is manufactured under strict sanitary conditions from fresh material derived from slaughtered and properly inspected animals. The same raw material may yield gelatin or glue depending upon the skill and care bestowed upon its manufacture. Gelatin does not exist ready-formed in nature, but is produced by the action of boiling water on collagen or ossein. The change of collagen into gelatin is a process of hydrolysis. The residue left over after the removal of glue is suitable for the manufacture of either bone meal or superphosphate. Di-calcium phosphate is obtained from bones in the process of preparing glue or gelatin. It is used as fertilizer and in the preparation of tooth powder and tooth paste. Better quality conforming to pharmaceutical standard is used in preparation of calcium tablets. Bones and horn pith contain ossein. Collagen content of bone ranges from 12 to 18% by weight. Some soft parts of animal offal are also rich in collagen. Rejected hides or skins, hide trimmings, skins from unborn animals, tendons, sinews, fleshings, etc. are used for glue or gelatin production. Such materials are called ‘glue stock’. 6.5.3.5. Bone Gelatin Gelatin is used as sizing agent in textile industry. Leather dressing, in ice cream, jellies, soft chocolates, as foaming agent, in making capsules, as binder in tablets, and as plasma expander in blood transfusion. Glue is largely used for the preparation of emery paper, and in the paper, textile and wood industries.

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6.5.4. Horns and Hoofs The horns of cattle, buffaloes and sheep and hoofs of cattle, buffaloes, sheep, goat, horses are considerable value (Figure 6.3). The horn and hoof meats which are rich in nitrogen (14%) are in great demand in Pakistan for use as manure in treatments and coffee plantation. Buffalo horns are used for the manufacture of combs, knife handles, snuff boxes, button toys and fancy articles. The waste material from these industries can be used in manufacturing of soap and oleic acid used as a lubricant for precision instruments. Impure variety of the oil is used leather dressing and in the textile industries. Recently, horns and hoofs have been processed for manufacturing molding powders, which can be worked in the same manner as synthetic molding powders.

Fig. 6.3 Utilization of Horn and Hoof Waste Source: Sannik et al. (2013)

6.5.5. Guts The guts from cattle and buffaloes go into the making of sausage casing for human consumption. The intestines obtained from slaughtered animals are carefully removed, washed thoroughly and processed after eliminating portions having defects like holes, blisters and pimples. Besides, guts from cattle, dried bladders and weasands (esophagus) are also used for making sausage. In Pakistan, little over 1% of the guts are used to produce casings for sausages and rest of the guts are converted into food and musical and tennis strings. Preservation of casing is done mostly in dry form and sometimes in wet form with common salt. Freeze drying of natural sausages casing eliminated lengthy preservation process and reduces weight during transport. The sorting of animal casing after salting for at least one month ensures the destruction of any pathogenic organism present. The product obtained by keeping animal stomachs and intestines overnight in boiling water in a bone digester and then steaming and drying them is suitable as a feed for pigs.

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6.5.6. Glands Glands from the animals slaughtered for meat production is a very good source of raw material for the manufacture of pharmaceuticals. Glandular products of animals are of two kinds, viz. hormones secreted from endocrines and extracts obtained from external secretory glands like liver. The nature of most of the glandular products that are manufactured from them is such that the glands and organs must be collected and processed as quickly as possible to avoid deterioration. Glands should never be in direct contact with the water because the active principles may be partially or totally leached out. A proper utilization of the glands is effected only in the slaughter houses in big cities where the large pharmaceutical firms collect them in time and make use of them. In smaller slaughter houses where facilities for collection are lacking, only the liver is used for human consumption. Liver extracts containing haemopoietic principles are prepared from ox and sheep livers.

6.5.7. Animal Hair The hair from tail stumps of fallen and slaughtered cattle and buffaloes is used in making various types of brushes. Different types of hairs are obtained from different breeds of goats in Pakistan. The various types of goat hairs are useful in the manufacture of blankets, upholstery, pile fabrics, men's summer suitings, linings, rugs, braids, nets, shoe laces, bats, decorative trimmings, shoe wigs, switches, curtains, bed spreads, bags etc.

6.5.8. Blood Blood is one of the valuable byproducts of the slaughter houses. It is of considerable value and finds use as manure. Blood-meal is used for feeding animals and as human food mixed with minced meat for sausages. Blood of the animal is a liquid consisting of about 80% water and 20% dry solids. The composition may vary slightly with type and age of the animal. Whole blood contains a high percentage of protein, i.e. 17-19%, and if extracted in a hygienic way from sound and healthy animal, can be used for human consumption. However, for practical reasons, a large proportion of the blood is not hygienically recovered and is either wasted or converted into blood meal. The approximate quantity of blood recovered as a percentage of the live weight of the different species of animals may be as follows (in %): cattle/buffalo 3-4, pigs 3-4, sheep/goats 3.5 to 4. The care and collection of blood depend upon the type of use of the blood. For utilization, as human food, the blood should be collected in clean receptacles. Various types of collection equipments are used ranging from a simple hollow knife connected to a piece of very thin plastic hose to sophisticated knife, some with builtin flushing and sterilization systems. Where blood plasma or blood albumin is required, blood collection should be done immediately after slaughter in an anticoagulant. It should then be centrifuged and the plasma so obtained, stored in

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polyethylene bags or bottles in a frozen condition. Where fibrin is required, the fibrin is to be stored at chilling temperatures in a stainless-steel container. The fibrin collected should then be washed with water until nearly white, and dried and preserved for human consumption. The flow diagram showing processing of blood is shown in Figure 6.4. For utilization as livestock feed, blood should be collected immediately without soiling with sand, mud, floor washings etc. in drums and buckets. It should then be transported immediately (within three to four hours) in closed vehicle to a place of processing. For use in pharmaceuticals, collection should be done directly as the blood flows out of the incision, preferably blood should be recovered aseptically by trocar knife and cannula in a closed container and should be chilled immediately. For the use in fertilizer, split and soiled blood should be collected in drums or buckets and should be transported (within four to six hours) in closed vehicles to a place of processing. The blood can be preserved by using 2% formalin or 2% Lysol based on the mass of blood.

Fig. 6.4 Flow Diagram of Processing of Blood Source: Williams (2013)

Industrial uses of the blood include pure concentrates of hemoglobin, protein globulin, and adhesives in plywood manufacture, foam rubber production, dyeing of textiles and papers, and dressing of leather before dying.

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References Coutand, M., Cyr, M., Deydier, E., Guilet, R., and Clastres, P. (2008). Characteristics of industrial and laboratory meat and bone meal ashes and their potential applications. J. Haz. Mat., 150, 522-532. Cunha, A., Feddern, V., Marina, C., Higarashi, M. M., de Abreu, P. G., and Coldebella, A. (2013). Synthesis and characterization of ethylic biodiesel from animal fat wastes. Fuel, 105, 228-234. Edström, M., Nordberg, Å., and Thyselius, L. (2003). Anaerobic treatment of animal byproducts from slaughterhouses at laboratory and pilot scale. Appl. Biochem. Biotechnol., 109, 127-138. Franke-Whittle, I. H., and Insam, H. (2013). Treatment alternatives of slaughterhouse wastes, and their effect on the inactivation of different pathogens: A review. Critical Rev. Microbiol., 39, 139-151. Jayathilakan, K., Sultana, K., Radhakrishna, K., and Bawa, A. S. (2012). Utilization of byproducts and waste materials from meat, poultry and fish processing industries: a review. J. Food Sci. Technol., 49, 278-293. Lasekan, A., Bakar, F. A., and Hashim, D. (2013). Potential of chicken by-products as sources of useful biological resources. Waste Manage, 33, 552-565. Mirzaei-Aghsaghali, A., and Maheri-Sis, N. (2008). Nutritive value of some agroindustrial by-products for ruminants-A review. World J. Zool., 3, 40-46. Moreki, J. C., and Keaikitse, T. (2013). Poultry waste management practices in selected poultry operations around Gaborone, Botswana. Intl. J. Curr. Microbiol. App. Sci., 2, 240-248. Sannik, U., Reede, T., Lepasalu, L., Olt, J., Karus, A., Põldvere, A., Poikalainen, V. (2013). Utilization of animal by-products and waste generated in Estonia. Agron. Res., 11, 255-260. Williams, P. T. (2013). Waste Treatment and Disposal: John Wiley and Sons Inc. NJ 07030, USA. Zia, U., Mahmood, T., and Ali, M. (2011). Dairy development in Pakistan. Food and Agriculture Organization, Rome, Italy.

Chapter 7

Domestic Waste Generated in Rural Areas Faizan ul Haq Khan, Abdul Nasir Awan and Shafique Anwar*

Abstract The domestic waste is comprised of solid waste (ash, rubbish and garbage), sludge and human excreta which is biological in nature. Ash alone is generated as 750 to 830 kgm-3 in weight and it is very difficult during collection and disposal. Nonbiodegradable part of domestic waste is consisted of combustible and noncombustible substances which vary in ratio of generation as 450 to 900 kgm-3 and needs proper care and attention during collection, storage, processing and disposal. Valuable products can be received by using different management and disposal techniques to maintain quantity and quality of the product by weight. All these sources are the biggest cause of health, sanitation and environmental problems and needs to be addressed during collection, storage, processing, and transporting at the time of disposal by various techniques. To avoid these problems, frequency from collection to disposal needs to be reviewed and proper adjustment to increase the efficiency of a system. The equipment used to perform different operations must be designed according to the use. However, Proper education and motivation from door to door, collection of waste must be encouraged to uphold the quality of cleanliness in true latter and sprite. Therefore, Environment friendly techniques for waste disposal must be introduced to achieve the positive results of the system, which will recondition and enhance the fertility level of the soils in rural areas. Keywords: Refuse collection, refuse storage, refuse processing, landfill, refuse collection equipments, disposal, composting, domestic latrines.

*

Faizan ul Haq Khan˧, Abdul Nasir Awan and Shafique Anwar Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding Author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan-ul-Haq Khan University of Agriculture, Faisalabad, Pakistan.

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Introduction

The domestic waste consists of solid waste (ash, rubbish and garbage), sludge and human excreta. The ash is the residue from the fire used for cooking and heating. It weighs 750-850 kg m-3. The ash may create nuisance during collection and disposal. The rubbish includes all non-putrescible waste except ashes. Rubbish comprises combustible and non-combustible substances such as paper, clothing, bits of wood, metal, glass, broken crockery, dust and dirt. The garbage is the organic waste matter resulting from the growing, handling, cooking and consumption of food. It consists of waste food, vegetable peelings and other organic matter. Its quantity varies throughout the year. It weighs 450-900 kg m-3. It needs careful handling because it breeds flies and other insects, supplies food for rats and decomposes rapidly resulting in unpleasant odour. Valuable products like grease, fertilizer and animal food may be recovered through the reduction, composting and other processes. The sludge is the waste water disposed from the kitchens and bathrooms by means of irregular, open and unlined channels. The street refuse is usually non-putrescible and is of concern as a source of fly breeding or bad odour. It weighs 700-850 kg m3 . Human excreta are source of infection. It is an important cause of environmental pollution. The health hazards of improper excreta disposal are: soil and water pollution, contamination of foods and propagation of flies and other insects. The waste characteristics like bulk density, viscosity, compaction behaviour, acidity, calorific value, moisture, volatile matter, ash, fixed carbon, sulphur and halogen contents are important in deciding the final disposal system. There are materials requiring special analysis or characterization for an insight to their behaviour in landfill, incinerators or when combined with other substances. For example, determination of the amount and composition of gases generated by microbiological organisms from organic chemicals in land fill.

7.2.

Storage and Collection

The average waste production from houses, shops, markets, offices, cottage industries and street litter is of the order of 0.42-0.5 kg per capita per day on an average per day in different urban areas of Pakistan. However, in rural areas of Pakistan, the quantity of waste production is much less. In Pakistani villages, the domestic refuse which mainly consists of solid waste is thrown in the open space, causing nuisance and dirty look. The refuse should be stored first at house level before taking it to a central place by sanitation organization/agency/authority. House-to-house collection is the best method of refuse collection. In Pakistan, this system does not exist. In villages, people throw refuse in front or around the houses in the streets. As the roads are mostly kachcha the refuse becomes the part of road and thus a source of nuisance and looks ugly.

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The Public Health Engineering and Sanitation Department recommended that local bodies should arrange for collection of refuse not only from public bins but also from individual houses. A house-to-house collection will result in a simultaneous reduction in the number of public bins. A recent innovation in the western countries is the 'paper sack'. Refuse is stored in the paper sack and the sack itself is removed with the contents for disposal and a new sack is substituted (Bond et al., 2011). Adequate number of containers should be provided for collection. The public should be educated for proper storage of refuse. Many countries have enacted ordinances regarding the refuse sanitation programme which contains specifications for house storage of refuse. The galvanized steel dust bin with a close-fitting cover is a suitable receptacle for storing refuse. The capacity of the bin depends upon the number of users and frequency of collection. All metal-can systems have the disadvantages both for the residents and for refuse collectors. The cans are difficult to clean. They are often dirty, usually dented and/or cracked, and are a nuisance to carry to the curb and back on collection days. For the collectors, the can is dangerous if not maintained properly, is always noisy to empty and is difficult to empty without spillage and worst of all is about a third of the total weight which the collector should lift every day. Public bins cater to many people. Galvanized bins of about 100 liter capacity can serve about ten families. They are usually without cover in Pakistan because people do not like to touch them. They are kept on a concrete platform raised 5 to 7.5 cm above ground level to prevent flood water entering the bins. This of course, appears to be the perfect solution in terms of hygienic storage, collection efficiency and the health of residents and workers, but it requires a significant initial expenditure by the local authorities and very high standard of human behaviour.

7.2.1. Problems Needs to be encountered Following problems are likely to be encountered (Blackman and William, 2016): (i)

Loss of bins by theft,

(ii)

Failure to replace lids and their subsequent disappearance,

(iii)

Interference by man and animals, including mischievous behaviour,

(iv)

Traffic accidents caused by bins rolling on the road,

(v)

Two men would be required to lift 100litres of high density wastes.

A mild steel dust bin of 60 liters capacity as mentioned in (Figure 7.1) can be used for collection and removal of solid waste. The 200 litre drum used for the distribution of oil, liquid fuels and similar products may also be used as waste container. This is cheap and within the limits. It is portable. The extent to which a drum is portable depends upon the nature of the contents. For refuse with a density of 500 kgm-3, the total weight will be about 115 kg. In the case of light packaging wastes, gross weight may be less than 35 kg. Even in the case of light packaging wastes, handling should always be by two men, because of the awkward size of the drum and its lack of lifting handles. At the maximum weight, it cannot be carried but it can be rolled on the bottom rim and emptied into a low vehicle.

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Fig. 7.1 Sixty Liter Dustbin When 200 litre drums are used as communal containers, the following problems may arise due to human behaviour: (i)

Throwing of the wastes around and not inside the bin,

(ii)

Overturning of the drums by scavengers in search of the salable materials or by herdsmen who may expose the food wastes to their animals.

However, it is possible to use 200 litre drums with reasonable success if following practices are followed by local authorities. (i)

The drums should be painted inside with bitumen paint to preserve them and on the outside with high gloss paint in a bright colour.

(ii)

Location should be carefully selected and where necessary paved and provided with partial fencing.

(iii)

Excess capacity should be provided to avoid overflow at peak periods of waste generation.

7 Domestic Waste Generated in Rural Areas (iv)

Damaged bins should be quickly replaced.

(v)

Collection should be done daily.

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Fixed storage bins may also be used for the collection of waste. This type of container is usually built from concrete blocks. The walls are of suitable height for wastes to be dropped inside over the wall (1.2-1.5 m). Capacity is rarely more than about 2 m3. In one wall an opening covered by a flap, is provided through which the wastes are raked out by the collectors. The real objection to this type of container is the extraction by rake through an opening at ground level. If the material was free flowing like coal this would work well. But wastes tangle together and in practice it is often impossible to remove them through a relatively small aperture, in the way the designer intended. The collectors have to climb and fill their baskets from the top of the heap, thus exposing large areas of their bodies to contact with the wastes. Besides the flaps covering the bottom opening tends to break off and disappear so that the contents overflow at that point. This encourages people to dump their wastes on top of the overflow and the result is storage by the side of the container, not inside it.

7.2.2. Frequency of Refuse Collection The frequency of refuse collection is decided carefully to avoid nuisance from offensive odours and fly breeding as the wastes of developing countries are high in vegetable-putrescible matter. As the refuse storage premises cannot be of unlimited capacity, any irregularity in collection service contributes to nuisance and hazards which result in poor sanitary conditions. The main factors which concern frequency of collection are: character of the wastes, climate, communal or house storage, characteristics of dwelling, duties of house bolder and cost.

7.2.3. Routes of Refuse Collection The routes of refuse collection should be so arranged that the distance hauled by the fully loaded vehicles to disposal sites is as short as possible. The information is collected for tentative routes regarding the number of houses served, average density per block, time required to serve various portions of routes, capacity of vehicle utilized in completion of the route, etc. Adjustments are done to facilitate economical use of labour and equipment.

7.2.4. Cost of Refuse Collection The average unit cost of collection cannot be worked out due to large variation in labour cost, frequency of collection, type of service, terrain, disposal methods, local factors, etc. The cost of refuse collection has been expressed in tons-kilometer unit, per capita unit etc. However, actual cost of refuse collection can be worked out only after studying the conditions of a village.

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7.2.5. Records of Refuse Collection Maintenance of proper records is very helpful for financial and operational controls. The main data include daily or frequent refuse collections (weight and volume), financial data, labour records, daily operational reports etc. The operational report prepared by the collection crew should include the vehicle number, its capacity, distance covered, volume and weight of refuse collected, number of premises from which no collection could be done and the reason therefore, pay roll for workers, complaints and their disposal, etc.

7.3.

Refuse Collection Vehicles

Refuse collection is the process of transferring solid wastes from the storage receptacle to the place of disposal. The process involves emptying the storage containers into a vehicle. This can be organized in different ways and various transport methods may be employed ranging from carrying on head or hand cart to 30 ton vehicle, Refuse collection is very costly and both the vehicles and methods most appropriate to local conditions in terms of quality of service and cost of operation should be selected (Yaws, 2014). Vehicles relevant to the conditions of the villages or developing countries are only dealt here. The important considerations in selecting the equipments are the vehicle size, loading height, type of refuse, kerb or carry out, pick up service, man power etc. The equipment should be provided with suitable covers. The vehicles should be watertight. This capacity depends on the rate of loading, length of haul to refuse disposal site, types of roads, bulk density of refuse etc. The collection of refuse in the villages may be termed as short-range transfer. The refuse may be collected from door to door by a small non-motorized vehicle such as hand cart and animal cart. However, small motorized vehicle may also be used in big villages or small towns of Pakistan.

7.3.1. Handcarts Handcarts are conventionally used in Europe for street sweeping because they cause minimum obstruction and their capacity is enough to keep a sweeper busy for up to two hours. They are also used in parts of Asia for daily house-to-house collection, especially in very narrow streets inaccessible to motor vehicles. In Pakistan, handcarts, mentioned in (Figure 7.2) are often open boxes, and the only means of transferring the contents to a large vehicle is to dump them on the ground and use a shovel or a basket for reloading. This is wasteful of labour and increases vehicles standing time. However, these types of handcarts are suitable means for the collection of refuse in Pakistan villages. The capacity of the handcart varies from 200 to 500 liters.

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Fig. 7.2 Refuse Collection Vehicles A six bin handcart (Figure 7.3) can also be employed for house-to-house refuse collection. One six-bin handcart load would be equivalent to about 50 dwellings at 8 liters per dwelling per day and one collector would be able to serve from 200 to 3.0 dwellings/day. At a density of 500 kg m-3, the weight per load would be about 200 kg excluding the cart, and this is well within the capacity of the average man to push, unless there are very steep hills, if wheels and bearings are of good design.

Fig 7.3 Wheel Barrow for Three or Six Buckets

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7.3.2. Pedal Tricycles Pedal tricycles with a box carrier in front still used by goods delivery people is commonly used in most parts of Pakistan. This can be adapted to carry wastes, but their volumetric capacity is less than a handcart. They reduce travel time and can therefore, operate over a larger radius than a handcart. However, the rural roads should suit the operation of pedal tricycle. They are used in China by self-employed refuse collectors who serve about 200 dwellings per day.

7.3.3. Animal Carts Horses, mules, bullocks and buffaloes are used in many parts of the world for doorto-door refuse collection. The capacity of draught animal carts ranges from 2-4 m3 and they often have tipping bodies either by pivoting the body or the use of a manually operated worm and nut. Animal carts have the following advantages: (i) There is no consumption of fossil fuels; (ii) The cost of animal cart is very low compared with motor vehicles; (iii) The operation is almost silent; (iv) The driver can leave the vehicle and assist in loading. Slow speed limits their effective radius of operation to about 3 km. In busy streets, they may interfere with motor traffic. This point is valid while they are travelling during collection. However, a stationary motor vehicle is equally obstructive. There is a need to give much greater attention to the design of animal carts for the collection of refuse. They should be low loading steel bodies mounted on pneumatic tyres, and fitted with sliding shutters and manually operated tipping gear.

7.3.4. Motor-tricycle The two-stroke, three-wheel motorcycle fitted with high level tipping body of about 2 m3 capacity can be used in big villages. The vehicle is particularly suitable for the villages where the streets are too narrow to admit larger vehicles. Its relatively high speed gives it an operating radius of about ten kilometers but it does not operate well on the rough roads.

7.3.5. Tractors and trailers One kind of motor vehicle which is almost universally available in developing countries is the agricultural tractor (Figure 7.4). It has several attractions: (i) Maintenance facilities are more readily available than for most other types of vehicle; (ii) It can haul a large load relative to its horsepower; (iii) It is an ideal vehicle for operating on rough roads because of its large tyres and high torque;

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(iv) It has a power take off from which hydraulic tipping gear on a trailer can be operated.

Fig. 7.4 The Simple Tractor and Trailer, used for Secondary Collection However; the cost of the tractor with trailer is very much high to be borne by local authorities and its use is only justified where the quantity of waste generated is high. There are several variants of tractor trailer systems. Mini-agricultural tractors or jeeps can be used with shuttered side-loading trailer up to 4 m3 capacity. Hydraulic tipping gear is operated by a power take-off. The agricultural tractor and trailor is often used as, a continuously coupled unit for the collection of refuse from house or communal storage points but it also has great potential as a transfer unit because of the ease with which the prime mover and the 'body' can be separated.

7.4.

Basic Collection Systems

Four basic collection systems have been evolved in relation to the amount of work imposed upon the householder (Yaws, 2014): (i) Communal storage which may require delivery of the wastes by the householder over a considerable distance; (ii) Block collection, where the householder delivers the wastes to the vehicle at the time of collection; (iii) Kerb-side collection, where the householder puts out and later retrieves the bin; (iv) Door-to-door collection where the collector enters the premises and the householder is not involved in the collection process.

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7.4.1. Collection from Communal Sites The use of large communal storage sites greatly simplifies the organization of refuse collection. However, when sites are widely spaced, a great amount of domestic wastes are deposited in the streets by householders due to laziness to carry it to the depot or masonry enclosure, While the use of large communal sites may appear to be, a fairly cheap and simple solution, it may transfer much of the burden of refuse collection on to street cleansing service and actually increase total costs, because sweeping from the streets is costlier than the collection of the refuse directly from a house. The use of large widely spaced communal storage sites is usually a failure because the demand placed on the householder goes beyond his willingness to cooperate.

7.4.2. Block Collection In this system, a collection vehicle travels along a regular route at prescribed intervals, usually every two or every three days and it stops at every intersection, where a bell is rung. At this signal the residents of all the streets leading from that intersection bring their waste containers to the vehicle and hand them over to the crew to be emptied. A crew of one or two men is adequate as they do not have to leave the vehicle. The frequency of collect ion in this system should be more, otherwise the weight of the wastes to be carried to the vehicle may be beyond the capacity of some of the residents. It has significant advantage over a kerb-side collection in that bins are not left out on the street for long periods. The daily performance achieved by this system is about 3.5 tons per man per day and 7.0 tons per vehicle per day.

7.4.3. Kerb-side Collection The kerb-side collection system requires a regular service and a precise schedule like the block collection. Residents must place their bins on the footway in advance of the collection time and remove them after the bins have been emptied. It is very important that the bins of a standard type are used, otherwise it is likely that wastes will be put out in improvised containers, such as cardboard boxes, or even in loose heaps. Under this situation some of the wastes are inevitably scattered by animals and wind, thus increasing the work of street cleansing. Kerb side collection is never entirely satisfactory for the following reasons: (i) Bins may be stolen (ii) Rolling of the bins on the road may cause traffic accidents (iii) Bins may be turned over by goats or cattle

7.4.4. Door-to-door Collection This is the system in which the householder does not work. The collector enters the premises, carries the bin to the vehicle, empties it and returns to its usual place. It is costly in labour because of the high proportion of working time spent walking in and

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out of the premises and from one dwelling to the next, but it is the only satisfactory system. A study conducted in USA showed that this system costs about twice that of kerb-side collection, but this ratio would be greatly reduced in countries where labour cost is low.

7.5.

Street Cleansing Waste

The sweeping of streets is such a simple job that it rarely attracts technical interest. It is a service for which a wide variety of tools, equipments and methods, both manual and mechanical, are available. There is often great scope for financial saving by the introduction of more efficient methods of sweeping. Much of the work for a sweeper arises directly from shortcomings in public behaviour, such as throwing litter in the streets. In some areas, a large proportion of street wastes is because of deficiencies in the refuse collection service because of which residents dispose of domestic and shop wastes in the streets. The cost of removing these wastes is much higher than the cost of collecting similar wastes from domestic waste bins or litter containers. For the purposes of solid waste management all street wastes fall into three main categories viz. natural waste, road traffic waste and behavioral waste.

7.5.1. Natural Wastes These include dust blown from unpaved areas, sometimes from within the village and sometimes from a great distance, and decaying vegetation such as fallen leaves, blossoms and seeds. Natural wastes cannot be avoided, but may be controlled by such measures as the careful selection of the types of tree planted in the village.

7.5.2. Road Traffic Wastes Road traffic wastes are of different types. They are excrement deposited by animals drawing vehicles, mud falling from trucks while moving to and fro to construction sites (in wet weather this can cause skidding of vehicles), oil deposited or spitted by major vehicles and tractors, and fodder and farm produce that drop off during transport.

7.5.3. Behavioral Waste The main source of waste is litter thrown down by pedestrians and house or shop wastes swept or thrown out. Human spittle and the excrement of domestic pets also fall into this category and together provide the main health risk by the inhalation of dust contaminated by dried spittle and excrement. Behavioral waste are largely avoidable provided an efficient refuse collection service is in operation and the litter bins are provided for the use of pedestrians. Success of this programme depends on public education backed up by legislation and rapidly operating enforcement procedures.

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Equipments for Road Cleansing

7.6.1. Brooms Brooms are of two main types-those formed from a bunch of long fibers and those which are based on a wooden stock into which are inserted numerous tufts of short filaments. The methods of using these types of brooms are fundamentally different. The bunch broom, which is long and flexible, is swept across the body in long strokes and the fibers exert very little pressure on the ground (Giusti, 2009). This makes it an excellent tool for sweeping litter and leaves from unpaved surfaces where minimum ground friction is desirable. The stock broom is pushed ahead of the sweeper with frequent short strokes to which much of the weight of the body can be applied. Thus, because of shorter and stiffer filaments, it is more effective in dislodging adhering matter and in collecting dust, partly because of sweeper's weight applied to it. Long handle broom (Fig. 7.5) has proved very useful for sweeping the roads. It reduces the blowing dust in the air and the operator need not bend his body. Thus there is considerable reduction in inhalation of the dust. It also helps in easy sweeping with less tiredness. The scraper used on the upper end of the handle helps in dislodging the dung, mud and other material from the road. This can be conveniently used even on kachha roads.

Fig. 7.5 Long Handle Broom

7.6.2. Shovel The conventional tool used for picking up small heaps of wastes and placing them in a receptacle, is large straight blade shovel. The shovel is ineffective when the wastes

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comprise largely of very light materials such as leaves, because they fall off or are blown away during transfer. A good solution to this problem is to use a pair of flat boards, usually plywood, between which the wastes are retained by hand pressure.

7.6.3. Hand Carts The time spent in working by sweepers for emptying basket containing street wastes can be saved if they are provided with hand carts. The gross weight of handcart may be as much as 250 kg in level areas and less in hilly regions.

7.6.4. Litter Bins Litter bin is an essential requirement if behavioral wastes are to be controlled. It should be of practical design, spaced at standard interval and emptied frequently. It should be non-inflammable because cigarette and beedi ends are often thrown into it. It should comprise an outer casing of standard colour and lettering, and an inner container which is easily removed by authorized persons for emptying. Size should relate to spacing and frequency of emptying, but the normal maximum should be about 100 liters which represents the upper limit for one person to lift and empty. Bins of 30 to 50 liters capacity can be mounted on street lighting columns by means of steel bands. The top aperture of a litter bin should be partly shielded to minimize loss of contents in high winds.

7.7.

Treatment and Disposal of House Waste

The villages are worse and insanitary in respect of house refuse disposal. Some parts of house refuse are fed to cattle. Dumping is mostly in trenches near the houses or sometimes on the plain ground. This causes constant nuisance of foul odour and flies. Nitrogen, phosphorus and potassium contents which form good manure are lost if the refuse is simply allowed to pile up on the ground and exposed to sun, wind and rain. Most of the decomposing organic matters attract flies. The flies may lay their eggs there. Covering the refuse with a little earth or burying it does not hinder development unless the refuse and the earth covering it are tightly packed. Over 90% of the world's solid wastes are disposed of in landfills (Giusti, 2009). There is no form of treatment that can entirely avoid the need for land for final deposit. As isolated sites are not easily available, the disposal method should be thoroughly evaluated. Several useful substances can be sorted from the refuse and hence the process should be divided into those of recovery and disposal. The valuable salvage may be obtained either by pre-separation by the householder or by separation at disposal site.

7.8.

Recovery of Refuse

The separation of salvageable matter may be performed at the control plant but considerable economy can be achieved by co-operation of householders in separation

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of salvage. For example, the paper when separated at the house is cleaner and has better market value. The economics should be worked out for the recovery and the additional costs required for multiple bins system of refuse collection. Glass, metals, plastics, leather, cloth trimmings, wood materials, garbage and miscellaneous commercial wastes have market value. Clean reclaimed paper may be re-used in the manufacture of paperboard or cardboard (Hoornweg et al., 2012). Recovered glass is of better value if it is sorted according to size and colour. The market value of recovered products should be carefully examined and the salvage operation should be conducted accordingly.

7.9.

Treatment of Kitchen Refuse

The kitchen wastes may be directly fed to the animals, after separating unwanted materials from it. However, if collected in the raw form, it should be treated before selling for animal feed. For treatment in a concentrator plant, they are discharged through a hopper to a picking belt for removing undesirable materials (Hoornweg et al., 2012). They are then passed to the concentrator (Figure 7.6), which is a steam jacketed cylinder with a central shaft passing through the cylinder and fitted with beater arms to agitate the refuse during cooking. A pressure of about 2 kg cm-2 is maintained in the inner cylinder during cooking. This ensures a sterile pudding of concentrate. The pressure is then released and moisture is drained for some time. The heat-treated refuse is received in stout bins in semi-liquid state, and then turned out after cooling for some time. The puddings may be packed in sacks for transport. If the kitchen waste is not suitable for animal feed due to its composition it can be fed into the biogas plants.

Fig. 7.6 Kitchen Refuse Concentration Plant Source: Husain et al. (1976)

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7.10. Separation of Salvage from Refuse When the refuse is to be disposed by incineration, dust and other materials of low calorific value should be separated from the refuse. During the separation, the salvage may be discharged into the receiving bopper of separation plant and then raised by belt elevator for feeding to the primary screen (Figure 7.7). The refuse may be carried forward in the screen by internal spiral. The speed of screen is about 15 rpm. From primary screen the dust is removed by a fine mesh (5 - 10mm) and material passing through 5 cm mesh is transferred to secondary screen through which the dust is further separated and the clean cinder is removed using a garbage extractor. The tailings from the primary and secondary screens and the garbage arc passed on a 1.2 m wide picking belt which moves at a speed of about 10 mpm for hand picking. A magnetic separator or magnetic pulley then separates the ferrous metal. Other usable material (glass, paper, rags, metal etc.) may be separated at picking belt. The remaining refuse may then be discharged by a moving tripping mechanism to a cross belt from where it may be charged into an incinerator or into a loading hopper to transport for controlled tipping or composting. Further, processing should be done for various sorted out substances.

Fig. 7.7 Refuse Separating Plant Source: Van Loosdrecht et al. (2016)

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7.11. Methods of Refuse Disposal The most common methods of refuse disposal are dumping, sanitary landfill, incineration, composting, reduction, grinding, salvaging, ploughing in the field, fermentation or biological digestion and burial.

7.11.1. Dumping Dumping is open throwing of refuse to fill up low-lying areas. The refuse should preferably consist of rubbish, ashes and street-washings, and exclude garbage. The method is popular but it is not quite satisfactory because of the risk to the public health arising out of breeding of flies and mosquitoes, scattering of papers by wind, obnoxious smell and fire hazards involved. In coastal areas, the garbage and refuse are dumped in large barges. The barges are towed by tugs and the refuse is dumped at a distance of 15-30 km from the shore to prevent the refuse being carried back to shore and causing a nuisance. The method is not satisfactory in rough weather because the barges cannot be discharged into the sea.

7.11.2. Sanitary Landfill Sanitary land filling is a simple, effective and cheap method of refuse disposal. Sanitary landfills require the refuse material to be placed in a trench or other prepared area. The depth of the trench is 3-5m and width 6m. For better biological degradation, the moisture content should not be less than 60%. The material placed in trench is adequately compacted and covered up with 15 cm layer of earth spread at the end of each working day. When the refuse is filled to a depth of 2-3m, it is compacted and covered with 1-2m earth. An ultimate settlement of 10-30% may be expected at most fills. The earth cover when properly compacted ensures that rats and other animals are prevented from burrowing and further odours and volatile gases do not escape through cracks. If the refuse has not passed through a separation plant, the materials like tins, rags, paper, bottle and other combustible articles should be picked up on the tipping face. The action in the fill is the organic decomposition because of which the fill area settles till it is finally stabilized in the soil in two to three years. Sanitary land fill is an efficient method of refuse disposal, provided regular supervision on the proper carrying out of the filling operations is deployed to see that the land fill does not deteriorate into an ordinary dump. The refuse-filled areas have been used for parks, golf courses, other recreational purposes, single story buildings etc. Tight packs (Figure 7.8) have been advocated for refuse disposal in rural areas but have seldom been adopted.

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Fig. 7.8 Tight Pack Source: Mahar et al. (2007), Bernal et al. (2009)

Tight packing prevents dissipation of the heat of decomposition, and many fly larvae are killed by the high temperature in the center of decomposing mass. No special implements or chemicals are needed and the contents of the pack after maturing for six months or so have manurial value. The refuse must be putrescible matter only, and stones, glass, tins, etc. should be removed. To make a good tight pack select a bard, level, rectangular piece of ground of suitable size and pack the day's refuse and dung along one shorter edge of the rectangle. If dung is not available, the refuse may be moistened slightly to produce a plastic mass that can be beaten into a compact rectangular block covering a corner or end of the selected ground. After the third day or so, its rear, sides and top are plastered over with mud; only the advancing face towards the other end of the rectangle are kept open. The daily additions of refuse are made to the open end only and plastered over on top and sides.

7.12. Basic Requirement of Sanitary Landfill According to the publication of the Environmental Protective Agency of USA, the disposal site should (Bernal et al. 2009): (i)

It should be easily accessible in any kind of weather to all vehicles used for disposing waste;

(ii)

Safeguard against water pollution originating from the disposed solid waste;

(iii)

Safeguard against uncontrolled gas movement originating from the disposed solid waste;

(iv)

It should have an adequate quantity of earth cover material that is easily workable, compactible, free of large objects that would hinder compaction and does not contain organic matter of sufficient quantity;

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(v)

Conform with land use planning of the area;

(vi)

It should be chosen with the highest possible regard for sensitivities of the community residents;

(vii)

It should be the most economical site available commensurate with the ultimate requirements for the waste disposal and be large enough to accommodate the community wastes for a reasonable interval.

7.12.1. Area requirement The area needed for sanitary landfill depends upon the volumes that will accumulate and on the depths to which they will be deposited, as well as on the density to which they will be compacted. Judging from the experience the density of solid wastes in a sanitary landfill varies from 225 kg m-3 under poor operation to 900 kg m-3 with excellent compaction. For planning purposes it can be assumed that 450 to 600 kg m-3 can be achieved. A refuse accumulation of 1.0 to 2.3 kg per capita per day is typical in rich rural areas.

7.13. Methods of Sanitary Landfill The following three methods are used in the operation of land fill: (i) Trench Method, (ii) Ramp Method, and (iii) Area Method

7.13.1. Trench Method The trench method is usually adopted where level ground is available. A long trench of 3 to 10m width and 2 to 3m depth is dug out depending upon local conditions. The refuse is compacted and covered with excavated earth. It is estimated that 0.4 hectare of land per year will be required for 10,000 population where the refuse is compacted in the fill to a depth of 2.5m.

7.13.2. Ramp Method Ramp method is well suited where the terrain is moderately sloping. Some excavation is done to secure the covering material.

7.13.3. Area Method The area method is suitable for filling land depressions, dis-used quarries and clay pits. The refuse is placed, packed and consolidated in uniform layers up to 2 to 2.5 m deep. The exposed surface of each layer is sealed with a mud cover at least 30 cm thick. Such sealing prevents infestation by flies and rodents and suppresses the nuisance of smell and dust. However, under this method supplemental earth is required from outside sources.

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7.14. Factors Affecting Sanitary Landfill Physical, chemical and bacteriological changes occur in buried refuse. The temperature rises to over 60°C within seven days and kills all the pathogens and hastens the decomposition process. Then the material is cooled down within two to three weeks. Normally, four to six months are required for complete decomposition of organic matter into an innocuous mass. The tipping of refuse in water should not be done as it creates nuisance from odour given off by the decomposition of organic matter. Recently the method of controlled tipping has been mechanized. The tasks of spreading, trimming and spreading top soil may be achieved with the help of bulldozer.

7.14.1. Superficial and Underlying Geology While selecting a site for landfill the soil and underlying rock conditions must be carefully evaluated. Soil characteristics are important from the stand points of drainage and availability of suitable cover materials for the landfills. The ground water table is equally important while selecting a site for landfill. Some investigators consider the upper surface of the ground water table to be the top of the capillary fringes or moistures zone. Generally, the sanitary landfills should not reach this zone, for leachate can then reach the ground water table. The bottom of the sanitary landfills should not be less than l.2 m above the ground water table level. The direction of flow of the ground water should also be studied carefully because the landfill may affect the ground water sources of drinking water. Sanitary landfill leachate is a potent liquid having a high pollution potential. A landfill site should be chosen so that it does not pollute any source of water supply.

7.14.2. Leachate Leaching of organic and inorganic matter present in crude refuse and the products of decomposition may take place by rainfall or ground water passing through the wastes. In a series of experiments it was found that a layer of refuse 1.5 m deep, compacted and covered with soil, would absorb rainfall for several weeks and thereafter produce a leachate equivalent to about one-third the annual rainfall (635 mm) in that area. This leachate was 20-30 times as strong as settled sewage, having a BOD of 6,000-7,000 mgl-1 and contained organic carbon, ammoniac and organic nitrogen, ammonia, chloride and sulphate. The leachate continued for several years but within less than three years pollutants had declined to a very low level except for the sulphate. This suggests that wastes should not be deposited in such a manner that water can pass through them to a stream or to an underground water supply.

7.14.3. Airborne Dust During long dry periods the surface of a sanitary landfill can become very dusty causing unpleasant working conditions for the men and excessive wear of vehicles and plant.

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Watering carts are frequently used to reduce this nuisance; and waste oils are suggested in sanitary landfill design and operation.

7.14.4. Surface Water Pollution The pollution of static water, ditches, rivers or the sea can occur when a sanitary landfill adjoins a body of water. The rain falling on the surface of the fill may percolate through it and may generate leachate which passes over an impermeable base to water at a lower level and thus causing the pollution. Only a portion of total precipitation emerges as leachate; some is lost by evaporation and transpiration. The quantity of leachate may increase substantially when upland water drains across the site of the landfill. However, worst case is when a stream crosses the site. The problems may be solved by diverting or culverting of all water courses which flow across the site, diverting upland water by means of drainage ditches and grading the final level of the site so that part of the precipitation is drained across the surface.

7.14.5. Manual and Mechanized Methods of Landfill Sanitary landfill is the formation of a number of contiguous embankments which may be referred to as strips. The filling material is dumped in heaps which are then spread out to form a level road and the flanks formed to the required slope. The sanitary landfill is possible by manual methods, as the landfill was developed before the invention of bulldozer. In fact, the manual method of operating sanitary landfill is appropriate to the needs of Pakistani villages and small towns. The needs of scattered communities may be served by operating a trench digging service if the terrain is suitable. An excavator may be taken from site to site on a low loader. It would excavate a trencher at each site with a capacity sufficient to contain the wastes of the community. At each site a man may be employed full time or part time according to the need and he would use the excavated material at the side of trench for covering wastes tipped into it. However, there are drawbacks in the manual methods. The reasons why sanitary landfill was mechanized are as follows: (i)

The very low density of filling material which initially occupies a very large volume; this can be reduced at the time of deposit by the use of heavy plant.

(ii)

Bulky wastes are quickly broken up by heavy plant.

(iii)

At suitable sites it is possible to excavate covering material from the sites by using machines instead of importing it.

(iv)

The use of mechanical plant reduced unit cost of operation in areas of high waste rates.

7.14.6. Methane Recovery Methane is produced in a landfill by the process of anaerobic digestion of the organic material contained in solid waste. Biodegradation of organic components starts as

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soon as the solid wastes are placed in landfill. Initially bacterial decomposition occurs under aerobic conditions because a certain amount of air is trapped within the landfill. As the oxygen is depleted, the anaerobic micro-organisms breakdown the complex long-chained organic compounds, primarily carbohydrates, to form organic acids. At a later stage methane-forming microorganisms become dominant. Methane recovered from landfills can be used as an energy resource. Many factors affect the feasibility of a gas recovery system at landfill. The age, size, moisture, average depth, quantity of refuse in place and potential end use of the gas are key factors.

7.14.7. Gas Composition Landfill gas comprises almost entirely one half methane and one half carbon dioxide, although the percentage by volume of both the methane and the carbon dioxide can vary widely. Typical landfill gas composition and characteristics of the gas are shown in table 7.1. Table 7.1 Typical Landfill Gas Composition and Characteristics Components Methane Carbon dioxide Nitrogen Oxygen Paraffin hydrocarbons Aromatic and cyclic hydrocarbons Hydrogen Hydrogen sulphide Carbon monoxide Trace compounds Characteristic Temperature (at source) High heating value Specific gravity

Component percent (dry volume basis) 47.5 47.0 3.7 0.8 0.1 0.2 0.1 0.01 0.1 0.5 Value 29° to 41°C 1,600 to 2,200 kJ/stdm-3 1.02 to 1.06

Source: (Bernal, 2009)

7.14.8. Collection System Landfill gas recovery wells have a diameter 30 to 90 cm and are drilled to bottom with a 7.5 to 15 cm diameter well casing perforated on the bottom-third to two-thirds (Figure 7.9). The well casing is installed on a layer of gravel. The well hole is backfilled 60 to 120 cm above the perforated portion of the well casing with crushed rock and concrete and/or clay air-seal is installed over the rock. Wells are often fitted with a butterfly valve for flow control. A landfill gas collection system which connects the individual wells to the pump is typically constructed with 10 to 20 cm diameter pipe. This gathering system may be

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above the ground or buried a few centimeters depending upon the end use of the landfill surface.

Fig. 7.9 Typical Well Configuration (not to scale)

7.15. Disposal of Refuse 7.15.1. Utilization of Landfill Gas The raw landfill gas is withdrawn using pumps connected to the collection manifold. The gas may be passed through a liquid-solid separator to remove condensate and particulates and then is compressed. The gas is then cooled and dehydrated. The gas then can be transported by pipeline to the location for use as for boilers, burners or electricity generation. Another alternative is to generate steam using a boiler at the landfill site. Landfill methane utilization brings the following three important environmental benefits: (i) Reduction or elimination of gas migration into areas next to the landfill site.

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(ii) Reduction in the nuisance of smell of gas which may otherwise bother the residents. (iii) Improvement in the quality of vegetation growing in the landfill as gas flows in pipes and not through the roots of grasses and plants.

7.15.2. Incineration Refuse can be disposed of hygienically by burning or incineration. It is the method of choice where suitable land is not available. The incinerator (Figure 7.10) in its simple form consists of a furnace provided with a grating and a chimney. Charging doors are provided for feeding refuse into the furnace. The burnt ash is removed through ash door. The weight of the ash is between 25 and 40% that of the incoming wastes and the volume between 10 and 15%. The high density of the ash makes it an economical material for transport. It can sometimes be used for land filling at sites where crude wastes are unacceptable. However, it does contain soluble inorganic salts which could cause water pollution.

Fig. 7.10 Incinerator This method is quite effective and has the advantage of destroying completely insects and pathogenic bacteria. However, because of the large amount of smoke and gas emitted in the process, it adds considerably to the air pollution problem besides damaging buildings and vegetation. Incineration is not popular in Pakistan because the refuse contains a fair proportion of fine ash which makes the burning difficult. A preliminary separation of dust and ash involves heavy outlay and expenditure besides manipulative difficulties in the incineration. Further, disposal of refuse by burning is a loss to the community in terms of the much-needed manure. Burning, therefore, has a limited application of refuse disposal in Pakistan. Incineration should not be adopted for small towns, villages, campus, hotels etc. unless good supervision and sufficient fuel are assured.

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Home-type incinerators, is recommended for the refuse disposal by individual house holders for reduction in total volume, but it contributes, substantially to air pollution through smoke and odour. In most of the home incinerators the developed temperature is not sufficient for complete combustion of garbage. The unused material may be disposed of by burial.

7.15.3. Composting Composting is a method of combined disposal of refuse and night soil or sludge and animal and agricultural wastes. It is a process of nature whereby organic matter breaks down under bacterial action resulting in the formation of a relatively stable humus-like material called compost.

7.15.4. Reduction In this process, the garbage is cooked under pressure. The molten fats can be separated and used for manufacture of soap, candles, or glycerin. The solid residue called tankage is used as fertilizer or cattle feed. This process is economical for large cities where sufficient garbage is collected and favorable market for finished products is available. However, reduction method is not popular due to bad odours, high cost of separate refuse collection, fire hazards involved in the extraction of grease with solvents like naphtha or gasoline, cost of equipments, unreliable market for finished products etc.

7.15.5. Grinding Grinding or pulverizing is the mechanical reduction of garbage in machines into a fine powder. The powder is used as fertilizer. Garbage grinding followed by discharging to sewers or to digester is being increasingly used in the USA and other countries. The number of house and commercial grinders has enormously increased in recent years. Home and commercial grinders do not create any difficulty in sewage collection system. Only the load of solids at treatment plant is increased by 0.05 to 0.015 kg per capita per day. Overloaded sewage systems may discourage the discharging of ground garbage into the sewers. When the ground garbage is discharged into the sewers, BOD and suspended solids increase by 20-25% and 25-35% respectively. Swing hammer mill are very commonly used to reduce the size of refuse. These are generally called shredders although they are often referred to as crushers, pulverizes, hoggers, grinders or mills. Shredders are vertical or horizontal types. Vertical shredders are sometimes two stage requiring only a single pass to get proper fineness of grind. Horizontal shredders are all single stage which means that both a primary and a secondary shredder are required in most instances. Shredding or size reduction is not a disposal method but merely a step in the final disposal of refuse which reduces difficult heterogeneous material to an easy-tohandle relatively homogenous material. The shredded refuse can be used for building compact landfills. Shredding also makes possible more efficient incineration or

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burning of refuse with crushed coal in a power-generating plant. Shredding is a prerequisite to the composting process, pulp recovery or pyrolysis. With the same degree of compaction pre-shredding reduces the refuse volume by as much as 50 to 65%. Hence, it saves on transportation costs.

7.15.6. Salvaging Salvage operations are practiced about disposal methods. Salvaged materials should be properly stored pending their utilization. Revenue from salvaged materials should be weighed against the additional cost of multiple bin collection system. Paper, metals, glass, rags, garbage etc. are principal marketable elements. Such salvaging is very helpful in disposal of refuse.

7.15.7. Ploughing in the Field This method of refuse disposal is used only on a small scale and is suitable for summer camps etc.

7.15.8. Fermentation or Biological Digestion Under this method garbage is placed in tightly sealed tanks to digest without air for ten days and then in the presence of air for 10 to 20 days. If necessary, the drainage collected at the bottom of the tank is recirculated to keep the garbage wet. The digested residue is stable and is a good soil conditioner. The recent innovation in the disposal of refuse by fermentation is producing biogas used for cooking, lighting and running internal combustion engines. The detailed discussion on biogas has been covered in Chapter 5.

7.15.9. Burial This method is suitable for small camps. A trench of 1.5 m width and 2m depth is excavated and at the end of each day the refuse is covered with 20 to 30 cm of earth. When the level in the trench is 40 cm from ground level, the trench is filled with earth and compacted, and a new trench is dug out. The contents may be taken out after 4 to 6 months and used in the fields. A trench of 1 m in length for every 200 persons will get filled up in about one week.

7.15.10.

Public Education

Refuse disposal cannot be solved without public education. People have very little interest in cleanliness outside their homes. Many union councils, town comities, municipalities and corporation usually look for the cheaper solution rather than efficient system regarding refuse disposal. The public should be educated on these matters, by all known methods of health education, viz. pamphlets, newspapers, broadcasting, films and telecasting.

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7.16. Excreta Disposal Human excreta are a source of infection and an important cause of environmental pollution. Every society has a responsibility for its safe removal and disposal. The provision of excreta disposal is listed by WHO Expert Committee of Environmental Sanitation among the first basic steps which should be taken towards assuring a safe environment in rural areas and small communities. The problem of excreta disposal is world-wide. Even in countries such as Great Britain, France and the USA, which by world standard may be considered as prosperous and healthy, much remains to be done in the field of sanitary excreta disposal. The improper excreta disposal may cause health hazards owing to soil pollution, water pollution, contamination of foods and propagation of flies. The improper disposal leads to several diseases which are not only a burden on the community in terms of sickness, mortality and a low expectation of life, but a basic deterrent to social and economic progress. The channels of transmission of disease from excreta are shown in Figure 7.11.

Fig. 7.11 Transmission of Disease from Excreta

7.17. Scope of Problems in Rural of Pakistan In most of the Pakistani villages, there are neither latrines attached to houses nor there are public latrines. The adults generally seek the open space, and children, old and sick people use the front or backyard of the houses or edges of streets for answering the call of nature. The excremental matter, both human and cattle, is found scattered near the houses. The dry crushed human excreta and cattle dung may be blown by wind and scattered on the surface of food and water (Qadir et al., 2010). The intestinal group of disease claims about 5 million lives every year while another 50 million people suffer from these infections (Remais et al., 2009). Surveys carried

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out in the community development of Pakistan showed that enteric group of fevers is very common in rural areas. Hookworm disease is also known to be highly prevalent; about five million people are estimated to be infested with hookworms. The solution to the problem is only through hygienic disposal of human excreta which is the central point of all public health services.

7.18. Method of Excreta Disposal The safe disposal of human faeces in rural areas is a tough problem. It is not that methods suitable for rural use, cannot be devised, it is because the rural population is not at all convinced that defecating in the open constitutes any danger to health. Nor do they favour the idea of latrines; they have seen public latrines in towns and have been revolted by the stench and filth. A deposit of faeces in a field may look ugly when fresh, but it soon dries up or is washed away, or is eaten by pigs, chickens etc. To a villager, it appears a hundred times more sanitary than a public latrine (Finley et al., 2009). The latrines in the villages should be for individual households and not public latrines. No one feels responsible for a public latrine, and it becomes very filthy. A latrine however, simple or elaborate, must satisfy two conditions. (a) Flies, insects or other animals should not have access, (b) The excreta should not contaminate any surface or ground water supply. Various problems arise if night soil is transported from a latrine to another place of final disposal. In Pakistan, only the sweeper caste will do such work, and they tend to be unpunctual, irregular and apt to exploit their monopoly. It would be a most valuable social reform if all of us could learn to handle and dispose of excreta sanitarily when necessary. During handling night soil is apt to be spilt out of containers and dumped in unauthorized places on its way to disposal. There are several methods of excreta disposal. Some are applicable to unsewered areas and some to sewered areas (Murtaza et al., 2010). These methods are discussed in the following pages.

7.18.1. Service Type (Conservancy System) The collection and removal of night soil from bucket or pail latrines by human agency is called the service type or conservancy system, and the latrines are called service latrines. The night soil is transported in night soil carts to the place of final disposal where it is disposed by composting or burial in shallow trenches. In some areas, the night soil is transported by animals or on the human heads. Service latrines are a source of filth and insanitation. They have all the drawbacks and faults which tend to perpetuate the disease cycle of faecal-borne diseases in the community. The night soil is exposed to flies. There is always the possibility of water and soil pollution. The buckets and pans are subject to corrosion and require frequent replacement. The emptying operation of the bucket is not always satisfactory. It is also difficult to recruit adequate staff needed for the collection of night soil. If the sweepers go on strike, the entire machinery collapses with dire consequences to public health.

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Furthermore, the employment of human labour for the collection of night soil is not consistent with human dignity and is no longer pardonable. However, in spite of all these drawbacks, it is desirable to improve the conservancy system to make it at least comparatively more hygienic because it will take a long time for adoption of sanitary latrines. The container (Figure 7.12) must be of improved standard design and should be supplied by the local authority. The container should be made from 24-gauge galvanized iron sheet of 45 cm, 22.5 cm × 12.5 cm size with slope of 12.5 cm on one side. It should be provided with handles on both the sides. It should have four to five holes for draining out the excess water and urine. The container should be painted with coal tar for the prevention of rust.

Fig. 7.12 Night Soil Container and Scraper The scrapers (Figures 7.12, 7.13) of standard design should be provided for cleaning the night soil container and bucket. A wheel barrow for three or six buckets may be used for carrying the waste. The sweepers should be given boots and hand gloves. The Public Health Engineering and Sanitation Department (in early fifties) recommended that in unsewered areas the service latrines should be replaced by sanitary latrines which require no service, and in which excreta can be disposed of at the site of the latrine in a hygienic manner.

Fig. 7.13 Night Soil Bucket and Scraper

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7.18.2. Non-Service Type of Latrines (Sanitary Latrines) A sanitary latrine is one which fulfills the following criteria: (i) Excreta should not contaminate the ground or surface water; (ii) Excreta should not pollute the soil; (iii) Excreta should not be accessible to flies, rodents, animals (pigs, dogs, cattle etc.) and other vehicles of transmission; (iv) Excreta should not create nuisance due to odour or unsightly appearance.

7.18.3. Trench Latrines A shallow trench 900 mm wide and 1,200 mm deep is excavated just outside the inhabited area, away from the direction of prevailing winds. Dry earth is stored nearly so that it may be spread by the user. The length of the trench depends upon the number of users. A length of 800 mm per seat may be provided ordinarily.

7.18.4. Bore Hole Latrine The bore hole latrine was first introduced in Pakistan by the ceramic factory, Gujarat during early fifties during campaigns of hookworm control. The latrine consists of a circular hole 30 to 40 cm in diameter dug vertically into the ground to a depth of 4 to 8 m, most commonly 6 m. (Figure 7.14). An earth-auger is required to dig bore hole. In loose and sandy soils, the hole is lined with bamboo matting or earthenware rings to prevent caving in of the soil. A concrete squatting plate with a central opening and foot rests is placed over the hole. A suitable enclosure is put up to provide privacy. For a family of five to six people, a bore of the above description serves well for over a year. Bore hole is essentially a family type of installation and is not recommended as a public convenience because of its small capacity. When the contents of the bore hole reach within 60 cm of the ground level, the squatting plate is removed and the hole is closed with the earth. A new hole is dug and similarly used. The night soil undergoes purification by anaerobic digestion and is eventually converted into a harmless mass. The merits of a bore hole latrine are: (i) It is cheap and easy to construct. (ii) There is no need for the services of sweeper for daily removal of night soil. (iii) The pit is dark and unsuitable for fly breeding. (iv) If located 14 m away from a source of water supply, there should be no danger of water pollution. Despite these merits, bore-hole latrines are not considered a very suitable type of latrines today. The reasons are: (i) The bore hole fills up rapidly because of its small capacity; (ii) A special equipment, the auger is required for its construction which may not be readily available;

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(iii) In many places, the subsoil water is high and the soil is loose with result it may be difficult to dig a hole deeper than 3 m, the bore hole latrine is therefore not very much in use today. It has been superseded by better innovations.

Fig. 7.14 Bore Hole Latrine

7.18.5. Dugwell Latrine The dug well latrine or pit latrine was first introduced in Pakistan in earlier fifty. It is an improvement over bore hole latrine. A circular pit about 70 cm in diameter and 3 to 3.5 m deep is dug into the ground for the reception of the night soil. In sandy soil, the depth of the pit may be lined with pottery rings and as many rings as necessary to prevent caving of the soil may be used. A concrete squatting plate is placed on the top of the pit and the latrine is enclosed with a superstructure. This type of latrine is easy to construct and no special equipment such as auger is needed to dig the pit. The pit has a longer life than bore hole because of greater capacity. A pit of 75 cm diameter and 3 to 3.5 m deep will last for about five years for a family of four to five persons. When the pit is filled up a new pit is constructed. The action of the dug well latrine is the same as in the bore hole latrine, i.e. anaerobic digestion.

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In a modification over bore hole and dug well latrines, the squatting plate is placed at the side of the hole or pit and connects it by a pipe going obliquely down (Figure 7.15). This arrangement does not necessitate moving the entire latrine when the hole is filled up, but another hole or pit is made at the side or back and again connected to a pipe sloping down from the latrine. The filled-up hole is covered with earth and in six months produces good manure. These latrines are not entirely sanitary because it is possible for flies to have some restricted access to excreta and breeding usually of blue bottle flies occurs.

7.18.6. Simple Septic latrine (Saral septic) The constructional details consist of tub, flap, trapseal, pit, cover of the pit and Ypipe (Figure 7.16). A rubber diaphragm is provided in a tin pan. The improved design of the latrine consists of an earthenware tub and a tin diaphragm. This arrangement provides darkness in the pit and after the night-soil has flown out, the diaphragm on the lid remains closed. This type of latrine is called simple septic latrine. This type of latrine has only one pit of 0.90 m × l.20 m × 0.90 m size dug at the rear of the latrine.

Fig. 7.15 Bore Hole Latrine (Modified) Source: Li et al. (2009)

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Fig. 7.16 Single Septic Latrine Source: Li et al. (2009)

7.18.7. Sopa Sandas This type of latrine is a ventilated improved double pit privy with a tin flap. The components of this privy are: (i) RCC stone slab with cement and mosaic W.C. pan; (ii) Steep sloping pipe with a tin flap at the upper end; (iii) Rectangular pit with a partial honey-comb brick lining; (iv) Y -pipe to connect both pits; (v) A vent pipe to carry away odours from the pit. The tin flap may be easily replaced when it gets worn out after several years. The waste is discharged in the pits alternately and valuable manure is available after digestion.

7.18.8. Water Seal (Pour Flush) Latrine A further improvement in the design of sanitary latrines for rural families is the handflushed "water seal" type of latrine (Figure 7.17). In this latrine, the squatting plate is fitted with a water seal. The water seal latrines have following advantages:

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(i) The water seal latrine, when properly operated and maintained satisfies all sanitary and aesthetic criteria; (ii) It can be installed near or inside the dwelling; (iii) It minimizes contact with flies and vermin; (iv) The odour nuisance is kept to minimum; (v) It is entirely safe for children; (vi) With improved construction techniques, it is simple to build and cheap for use in rural areas.

Fig. 7.17 Water Seal Latrine (Direct Type) Source: Li et al. (2009)

These merits have rendered the water seal type of latrine more acceptable to rural people than the bore hole or pit privy without water seal.

7.18.9. Designs of Water Seal Latrines Three designs of water seal latrines are most popular. These are: (i) RCA type, designed under the Research-cum-Action Projects in Environmental Sanitation of the Ministry of Health, Government of Pakistan. (ii) PRAI type evolved by the Planning, Research and Action Institute, Lucknow (Uttar Pradesh). (iii) NEERI Water Seal. Latrine designed by the National Environmental Engineering Research Institute, Nagpur. The parts of the water seal latrine, whether RCA, PRAI or NEERI type, are essentially the same. The differences are in matters of minor engineering details.

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7.18.9.1. RCA Latrine The safe distance between the latrine and a source of water supply depends upon the porosity of the soil, level of ground water, its slope and direction of flow. The latrines of any kind should be at a lower elevation to prevent the possibility of bacterial contamination of the water supply. Where possible, latrines should not be in areas usually subject to flooding. The recommended safe distance of latrine from a water source is: (i) If the soil at the depth of the soakage pit is of fine texture such as silt or clay (effective size 0.2 mm or less) and the velocity of flow of ground water is up to 1m/day, the latrine can be placed as close as 6 m from the well; (ii) If the soil is coarser than above the latrine should be placed at least 15 m away from the well; (iii) If the soil is very coarse, then a spot study should be done to decide the safe distance between drinking water source and the soakage pit. a.

Squatting Plate

The squatting plate or slab is an important part of a latrine. It should be made of an impervious material so that it can be washed and kept clean and dry. If kept dry, it will not facilitate the survival of hookworm larvae. In recommending plates, due consideration should be paid to the habits of Pakistani people who defecate in the squatting position and use water for anal washing. The slab of RCA latrines (Figure 7.18) is made of cement concrete with minimum dimensions of 90 cm square and 5 cm thickness at the outer edge. There is a slope of 1.25 cm towards the pan. This allows drainage of the water used for ablution or cleansing purposes into the latrine. A circular squatting plate of 90 cm diameter and of 5 cm uniform thickness has also been found to be satisfactory. For the convenience of the users, raised foot-rests are included in the squatting plate. Fig. 7.18 Squatting Plate Source: Li et al. (2009)

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Pan

The pan (Figure 7.19) receives the night soil, urine and wash water. The length of the pan is 42.5 cm. The width of the front portion of the pan has a minimum of 12.5 cm and the width at the widest portion is 20 cm. There is a uniform slope from front to back of the pan. The pan is given a smooth finish. Fig. 7.19 Pan Source: Li et al. (2009)

c.

Trap

The trap is a bent pipe, about 7.5 cm in diameter, and is connected with the pan. It holds water and provides the necessary ‘water seal'. The water seal is the distance between the level of water in the trap and the lowest point in the concave upper surface of the trap. The depth of the water seal in the RCA latrine is 1.9 cm (Figure 7.20). The water seal prevents access by flies and suppresses the nuisance from smell. Fig. 7.20 Trap Source: Li et al. (2009)

d.

Connecting Pipe

When the pit is dug away from the squat plate, the trap is connected to the pit by a short length of connecting pipe 7.5 cm in diameter and at least 1 m in length with a

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bent at the end. As the pit is sited away from the squatting plate, latrine of this type is called the indirect type (Figure 7.21). A connecting pipe is not required in direct type of latrine. The direct type is best suited for areas where the ground is hard and does not easily cave in. The direct type is cheaper and easier to construct and occupies less space. An advantage with the indirect type is that when the pit fills up, a second pit can be put into operation by merely changing the direction of the connecting pipe. Therefore, the indirect type is usually preferred.

Fig. 7.21 RCA Latrine (Indirect Type) Source: Li et al. (2009)

e.

Dug Well

The dug well or pit is usually 75 cm in diameter, 3 to 3.5 m deep and is covered. In loose soil and where the water table is high a lining of earthenware rings or bamboo matting can be used to prevent caving in of the pit. When the pit fills up, a second pit is dug nearby and the direction of the connecting pipe is changed into the second pit. When the second pit fills up, the first one may be emptied and reused. f.

Super-structure

The desired type of superstructure may be provided for privacy and shelter. An attractive superstructure with a neat finish is desirable as this will be generally well maintained. g.

Maintenance

The life of a latrine will depend upon several factors such as care in usage and maintenance. The latrine should be used only for the purpose intended and not for disposal of refuse or other debris. The squatting plate should be washed frequently and kept clean and dry. People should learn to flush the pan after use with adequate

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quantity of water. One to two liters of water is sufficient to flush the RCA latrine. Thus, proper maintenance involves health education of the people which is very necessary for the success of any latrine programme. 7.18.9.2. PRAI Latrine The constructional details of PRAI latrine are the same as that of RCA latrine except for the difference in the size of the pan and dugwell, and location of foot rests with respect to pan. The dug well of the latrine is sufficient for six to eight years for an average family. 7.18.9.3. NEERI Latrine National Environmental Engineering Research Institute, Nagpur, has developed this type of latrine. The emphasis of the Institute is to construct individual family latrine rather than community latrines. NEERI latrine (Figure 7.22) consists of a squatting room and a soakage pit. In the squatting area, a cement mosaic finish pan, a trap with 1.25 cm water seal and a connecting pipe is fitted to carry faeces to the soakage pit. The faeces along with ablution water and flushing water drop into soakage pit. Water is soaked by the- soil and faeces are digested anaerobically that results in humus rich in fertilizing constituents. The amount of this humus ranges between 20 and 75 liters per capita per year. The soakage pit is sufficient for three to five years for a family of five persons.

7.18.10.

Bavla Type (Band Flush) Latrine

The hand flush latrine is suitable in the areas where there is hard clayey soil with low water table. A pit of 75 cm × 82.5 cm × 240 cm size and of bucket shape is dug (Figure 7.23). The pit should be kept 7.5 to 9.0 m away from the drinking water well. The pit is provided with 45 cm brick work on the top for the proper placement of tub and seat and to avoid sliding of the soil into the pit. The W.C. Pan with 20 mm water seal monolithic cast together is directly placed over the pit. The night soil is converted into water, gas, etc. which are absorbed by the soil. The sludge is converted into manure. One pit of the above size may serve an average family for six to seven years. The water seal tub should always be filled with water. The latrine is flushed with 1-1.5 liters of water. It is desirable to keep always in the latrine a small pot filled with water.

168

Fig. 7.22 NEERI Rural Latrine Source: Finley et al. (2009)

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Fig. 7.23 Hand Flush Latrine Source: Finley et al. (2009)

7.18.11.

Latrine-Cum-Gas Plant

Latrines may be attached to the biogas plants for the generation of biogas. The gas plant is useful for the farmers who own five or more cattle heads. By attaching the latrine to the plant, human waste can also be used to produce gas enough for the fuel and lighting requirements of a family. KVIC design of biogas plant can be adopted for the operation of plant on night soil (Figure 7.24). The faeces from the latrine are collected in an inlet tank. The inlet tank is used for mixing the dung with water to be fed in the plant. The precaution to be taken is that a limited quantity of water should be used for ablution to avoid the unnecessary dilution of the feeding material.

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Fig. 7.24 Latrine-Cum-Gas Plant Source: Finley et al. (2009)

In another design of biogas plant which works only on night soil, the inlet of the gas plant is attached directly to the latrine pan by a pipe laid to a steep gradient. The W.C. pan is so designed that minimum water is required to flush the night soil to ensure proper dilution. The liquid slurry neither has an offensive odour nor does it attract flies. The slurry is left to dry in drying beds to be used as fertilizer. For increasing the benefit, individual gas plant owners allow the outsiders to use their latrines. The high initial costs in setting up a gas plant is recovered in five to six years in the form of gas and manure. However, systematic research data are not available on the performance of latrine-cum-gas plant.

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7.19. Septic Tank The septic tank is the most useful and satisfactory unit among all water-carried systems of disposal of excreta and other liquid waste from individual dwellings, small groups of houses and institutions located in rural areas out of reach of sewer system. A septic tank is a horizontal continuous flow one-storey sedimentation tank of masonry (cement plastered inside) or concrete through which sewage can flow slowly. Nearly 60 to 70% of suspended matter settles at the bottom and is retained until anaerobic decomposition is established. This process called as sludge digestion results in the changing of some of the suspended organic matter into liquid and gaseous substances, and reduction in the quantity of sludge to be disposed of. The sludge is removed at intervals of two to six months or more. The detention period of 24-48 hours gives best effluent after filtration for residential tanks. The usual practice is that the septic tanks are built underground. The absence of free oxygen and warmth created in a septic tank helps in flourishing the anaerobic bacteria. A bout 65% mineral matter is available in human excreta. The remaining 35% is organic matter. Only 20 to 40% organic matter (solids) are liquefied or gasified in the septic tank. The heavier matter (sludge) settles at the bottom and the lighter matter (e.g., grease and fats) forms a layer called 'scum' on the top. The tanks are made air-tight and water-tight. The sewage enters through T-piece on the left (Figure 7.25). The lower limb of T dips well into the liquid so that the incoming sewage does not disturb the scum formed on the surface.

Fig. 7.25 Septic Tank (in section) Source: Finley et al. (2009)

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The gases that collect above the liquid can leave via the outlet and be absorbed in the soil of the soaking trench, A vertical partition wall called ‘hanging baffle wall’ is built in the tank to take precaution against the disturbance of the scum and sludge. The close contact of sewage with the scum and sludge together with the agitation of the sludge by rising gases, make the effluent highly odorous, high in BOD and finely divided solid contents, with the possibility of containing pathogenic bacteria which are dangerous to human health. There is also the nuisance due to bad odours and offensive nature of the septic effluent. The septic tank can only be considered a primary treatment requiring a secondary treatment of the effluent for final disposal. The tanks are especially suited for isolated buildings and communities where sewers are not available. In the absence of ideal excreta disposal system there is a good scope for the use of septic tank in rural areas of Pakistan.

7.19.1. Design Considerations 7.19.1.1. Capacity of Septic Tank The capacity of a septic tank is the volume of liquid which it can accommodate. A septic tank should have a capacity to store the sewage flow for 24 hours and an additional volume of sludge for two to three years depending on periodicity of cleaning which should not be less than six months. If only water closets are connected to septic tanks, the sewage flow will be about 40-70 liters per capita per day. When sludge is also discharged to septic tanks, the sewage flow will be about 90-150 liters per capita per day. If large quantity of sludge is expected, which is rare in rural areas, it may be separately disposed of. The method suitable for sludge disposal in rural areas is described in the later part of this chapter. The rate of accumulation of sludge has been recommended at 30 liters per capita per day. 7.19.1.2. Shape and Dimensions of the Tank The tanks of rectangular section are easy to construct and most suitable from the functional point of view. However, circular precast tanks have been found more cheap and convenient for small installations. The chances of stagnant pockets are lesser but greater possibilities of short circuiting exist in circular tanks. Nevertheless, the short circuiting may be avoided by proper designing of inlet and outlet. The deep tanks allow better settling. However, for a given capacity, if the depth is increased, the surface area is subsequently reduced which will require higher vertical velocities of settling particles and there are chances of short circuiting. The minimum sewage depth should be l.2 to l.5 m adequate space should be provided above the sewage level to accommodate scum. Therefore, a free board of 30 cm is necessary. The tanks of greater length are less liable to be short-circuited between inlet and outlet. But the longer tanks do not increase the detention period. In the past, long and narrow tanks were recommended. For a given surface area, the width will be less if the length is more, consequently the velocity of flow through the tank will be more but the detention period will remain unaltered (as it is determined by the ratio of volume of tank to the discharge per unit time). Higher velocities will cause greater disturbance restricting the length of the tank. Also, too wide septic tank creates the

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stagnant pockets near corners. A ratio of 3:1 to 3:2 between length and width of the tank has been recommended. However, the width should not be less than 90 cm. 7.19.1.3. Inlet and Outlet of Septic Tank The inlet and outlet of the tank should be properly designed for its proper working. The construction should be such as to prevent direct currents between inlet and outlet, which ensures effective sedimentation. To avoid the short circuiting the distance between inlet and outlet should be as much as possible. The inlet and outlet should not be located at the same level. The inlet should penetrate to a depth of about 30 cm below sewage level and the outlet should penetrate to about 40% of the depth of sewage. The effective sedimentation may be achieved by using pipettes with submerged ends as inlet and outlets or alternatively with a baffle-wall at one or both ends for deflecting the flow. The baffles are better than inlet and outlet tees as they distribute the flow evenly along the width of the tank. When the baffles are used, they should be located 20-30 cm away from the walls and the ends of the inlet and outlet sewers are flushed with tank walls. Outlet invert should be kept at least 5.0-7.5 cm below the inlet invert. Greater level difference creates disturbance at the inlet. Inlet and outlet baffles or tees should extend about 20cm above the sewage line and leave a clearance of at least 7.5 cm below the cover for ventilation. 7.19.1.4. Covers and Manholes The tank is usually covered with R.C.C. slabs, removable or fixed with manhole covers to permit inspection or maintenance. The cover should be strong enough to take the earth load and live load likely to pass over it. For small tanks above the ground level, precast concrete covers may also be used which may be lifted for cleaning. The tank cover helps in keeping sewage warm, preventing wind agitation, lessening odours and preventing accidents due to falling in of children or animals. For the underground tanks, the covers should be watertight to prevent the entry of water from outside. For small single-compartment tank only one manhole may be placed over the inlet. But for bigger or two-compartment tank, another manhole should be provided for the outlet. A small inspection cover should be provided over the interconnection of two-compartment tank. 7.19.1.5. Ventilation The ventilation of the septic tank is required to remove the gases. If the soil pipe of the connected water closet is adequately ventilated, no ventilation of septic tank will be necessary. However, if ventilation is necessary a 5-10 cm diameter vent pipe may be provided on the wall or covering slab near the first compartment at the highest point so that it is not submerged into the scum of sewage. The vent pipe should be taken above roof level. The top end of the pipe should be provided with a mesh.

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7.19.1.6. Grease or Grit Traps Under normal conditions of domestic sewage, these traps are not necessary. However, a grease trap becomes necessary to be installed if the discharges from a big kitchen are to be treated. A grit trap is necessary if sand, ash or mud is used for cleaning utensils. The grit and grease traps are also necessary if wastes from floor washing and motor garage washing are discharged into the septic tank. A combined grease-cum-grit can serve both the purposes. 7.19.1.7. Lining of the Septic Tank The septic tanks should be watertight according to the standard specifications. The cement plaster of 1:6 may be used for plastering to create watertight conditions. 7.19.1.8. Working and Maintenance of Septic Tanks The sludge deposited in the septic tank must be removed once a year or so and should never be allowed to be deposited up to one-third depth of the inlet compartment. The removal of scum is not essential as it does not affect the working of the tank. An extra chamber called 'dosing chamber' is sometimes built in continuation of the tank. In this chamber a siphon is fixed. It discharges at intervals after certain quantity has been filled in. It helps in flushing the drain. The cast-iron pipes are used up to a length of 1-3 m from the house to the septic tank. Beyond that glazed earthenware pipes of 10-15 cm diameter may be used. The septic tanks are initially filled with water. The disinfectants should not be used excessively. The soaps and grease from bathrooms should be separated in grease traps as far as possible.

7.19.2. Dimensions of Septic Tanks The recommended capacities (including air space above liquid level) of septic tanks serving individual dwellings are given in Table 7.2. The necessary changes may be made depending upon the prevailing situations. Table 7.2 Capacities for Septic Tanks Serving Individual Dwellings Maximum number of persons served

Nominal sewage capacity of tank (liters)

4 6 8 10 12 14 16 Source: Grey (2010)

1,900 2.300 2,750 3,400 4,200 4,950 5,700

Width (m)

0.90 0.90 1.05 1.05 1.20 1.20 1.35

Recommended capacities Length (m) Sewage depth (m)

1.80 2.10 2.25 2.55 2.55 3.00 3.00

1.20 1.20 1.20 1.35 1.35 1.35 1.35

Total depth (m)

1.50 1.50 1.50 1.65 1.65 1.65 1.65

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7.19.3. Cleaning of Septic Tank and Disposal of Sludge The septic tanks may be got cleaned either manually by scavengers or mechanically by septic tank cleaning firms. The cleaning firms mix the entire content and pump it out into a tank truck with special equipment. Care should be taken to prevent the pollution of the surrounding ground by the spillage. The contents should be emptied into a sanitary sewer system or sludge digestion tank or in shallow trench or pit at a distance of 60 m or more from water sources and should be covered with compacted earth of minimum of 60 cm thickness.

7.19.4. Disposal of Septic Tank Effluent The septic tank does not fulfill the object of complete treatment of sewage. It removes suspended solids from the sewage, liquefies major portion of solids and conditions sewage to facilitate further disposal. The putrescible and highly odorous effluent from the septic tank should be properly treated and disposed of to be of minimum nuisance or risk to the health of the people. The effluent from a septic tank should not be discharged directly into streams or on the land. Septic tank effluents may be disposed of by direct methods or secondary treatment methods. The direct methods are sub-surface disposal, seepage or soak pit, land treatment, dilution and evapotranspiration, the secondary treatment include subsurface sand filters and filter trenches, open sand filters, trickling filters and small oxidation pond. 7.19.4.1. Subsurface Disposal (Irrigation) The method of subsurface disposal is also known as soakage gallery. The septic tank effluent is uniformly distributed into subsoil through open- jointed pipes or drains, laid near the surface of the ground enabling the effluent to percolate into the surrounding soil. The effluent is decomposed into compounds suitable for plants by nitrifying soil in the presence of air. The disposal by subsurface irrigation is favored where land is cheap and plentiful, subsurface strata are porous favoring large infiltration and subsoil water level is low. The absorption field (where the effluent from the septic tank is disposed of through subsurface irrigation) comprised distribution box, drain pipes and dispersion trenches. Distribution box is a chamber which ensures an even distribution of the effluent to the subsurface disposal field through drain pipes. For the purposes of equal distribution of flow among its various outlets, it is necessary that the flow should remain unobstructed so that the absorption field does not remain inoperative. Drain pipes may be either plain ended pipes made of unglazed earthenware or socket or spigot sewer pipes. With plain ended pipes, the upper half of the joint is to be covered with a strip of asphalt or tar paper to prevent entrance of sand and silt into the pipe joints. The socket and spigot pipes do not need this protection since these are provided with socket ends. The joints are covered with at least 5 cm of gravel. The dispersion trench enables the effluent from drain pipes to be absorbed into the subsoil. In general, a maximum length of 30 m may be adopted for the dispersion trenches as greater length may cause uneven distribution of effluent. A 15 cm layer of gravel and crushed stone is placed near the bottom. The pipes are then laid to the

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required grade (1 in 300 to 1 in 600). At least 5 cm and preferably 15 cm of finer material-well-graded coarse material should be laid on the top of pipe. The rest of the trench is then backfilled with ordinary soil or earth. 7.19.4.2. Seepage or Soak Pit The soak pit is a cover pit through which the effluent can be soaked or absorbed into the surrounding soil. The pit may be kept either empty or filled up with brick or aggregate. If the top soil is impervious and very porous stratum lies deep below the soil surface, this may be the only solution for the disposal of effluent. The capacity of seepage pit is decided based on percolation tests conducted in each pervious stratum. The effective area of the pit is generally the vertical wall area (based on dug diameter) of pervious strata below the inlet. The bottom area and the area of impervious strata are not considered. The soak pits are usually 1.0-1.5 m in diameter with a depth of at least 1.8 m. When empty, the pit is lined with brick stone or concrete blocks with dry open joints and with at least 7.5 cm backing of coarse aggregates. When filled, no lining is required except for a masonry ring constructed at the top of the pit to prevent damage by flooding of the pit by surface runoff. In stone-packed soak pits the sludge fills the voids and the blockage creates flooding on ground surface. The stones should be removed for drying, cleaning and refilling for proper functioning of the soak pit. The soak pit should not be used if there is a chance of contaminating underground water. Care should be taken in the use of soakage pits in localities where water supplies are obtained from private shallow wells. 7.19.4.3. Land Treatment (Irrigation) The septic tank effluent is distributed by a system of channels or carriers so arranged as to distribute the sewage effluent as uniformly as possible on land. The land's capacity of disposal of effluent may be increased by providing 0.6-0.9 m deep field drains 4.5 m apart which discharge into a ditch or water course. For sandy and gravelly soils about 15 m2 land is required per house. This method of disposal is not suitable for non-porous soils and waterlogged areas. It may pollute the source of water supply create unaesthetic conditions, nuisance, fly-borne contamination and mosquito breeding. 7.19.4.4. Dilution The sewage effluent may be discharged into the nearby river, lake or sea. This system takes the advantage of natural ability of water for self-purification. The receiving water may be contaminated with pathogenic bacteria in this system of disposal. As the water is used for bathing, drinking, washing clothes, irrigation of vegetables etc., and the effluent should be chlorinated before discharging into the streams. 7.19.4.5. Evapotranspiration The effluent is spread in thin sheets over areas in which dense vegetation is grown. It may be led through open-jointed pipes in trenches, the pipes being surrounded by graded gravel. Above gravel 20-40 cm coarse sand is filled. Over this 10-15 cm deep soil is provided for plantation. The evapotranspiration bed may be used as

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supplementary to the soil absorption systems where the percolation rates are unfavorable. It is especially suited for impervious and clayey soils, but unsuitable for waterlogged areas. The expected rate of evaporation from suitable vegetation is about 0.5 - 0.8 liter/m2/day. The evapotranspiration increases in the long day, good sun shine, less humidity, more temperature and air turbulence. If the conditions favorable to subsurface absorption system exist, the other direct methods should not be preferred. If needed, they may be used in conjunction with absorption system. However, if all the direct methods are not feasible due to various reasons such as impervious soil, limited area of land, water-logging, usable water courses etc. secondary treatment of effluent is necessary before final disposal on land or in surface water or underground water. 7.19.4.6. Subsurface Sand Filters and Filter Trenches In tight and impervious soils the trenches are constructed below the ground. The trenches are 1.2-1.8 m deep and 0.75-1.50 m wide, and filled with gravel and sand. The effluent is distributed through distributing open jointed pipes of 10 cm diameter and laid at 0.5% grade at the top of the bed. The pipes are surrounded with gravel. A cover of fill material and top soil is provided over the gravel. At least 60 cm of clean sand of effective size 0.4-0.6 mm is placed beneath the pipes and gravel. The open jointed collector pipes which collect the filtered effluent are laid on the bottom of the bed surrounded by the graded gravel. If more than one trench is required, sufficient natural earth should be left between them. For larger installations, the sand filters are preferred to trenches. Though the filtrate from subsurface filters and trenches is well treated and clear it may not be bacteriologically safe. The high water table affects their use. There may be problem of clogging of pipe joints and sand pores which require occasional removal and replacement. 7.19.4.7. Open Sand Filters (Intermittent) These filters are like subsurface sand filters but they are constructed above ground or partially above and partially below the ground. They are useful where the watertable is close to the surface and subsurface conditions are unfavourable. They produce stable and highly purified effluents, and are recommended for large institutions and communities which can afford them for sewage plant operations. 7.19.4.8. Trickling Filters Trickling filters are suitable under rocky or clayey soils, high water-table condition and where limited land is available. The filtrate from these filters is well stabilized and free from odour, but may be bacteriologically unsafe. The open filters breed moth which cause serious nuisance in the neighbor-hood. The loss of head is high in these filters, i.e. 1.5 to 2.0 m.

7.19.5. Small Oxidation Pond The effluents from septic tanks (anaerobic ponds) may be led to a small aerobic pond. Such a two-stage stabilization system effects better removal of organic matter and

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produces stabilized effluent. The main design consideration· of oxidation pond is the hydraulic and organic loading, sunlight, etc. Generally, a detention time of 2-9 days and organic loading of 70 kg ha-1 per day and 1.0m depth of water are satisfactory. The oxidation ponds should be away from inhabited areas and drinking water wells due to mosquito breeding nuisance in ponds and pollution. The effluents from secondary treatment units should be disinfected with chlorine before discharging to streams likely to be used by human beings or animals. The' desired residual chlorine is 0.5-1.0 ppm. If no secondary treatment is feasible, at least the effluent from septic tanks should be chlorinated before discharging into streams.

7.20. Imhoff Tank Imhoff tank was designed by Karl Imhoff of Germany. The Imhoff tank also combines sedimentation and sludge digestion like a septic tank. But in the Imhoff tank, sludge is digested in a separate compartment. A better effluent is obtained in Imhoff tank as incoming sewage or influent is not allowed to mix with the sludge produced, and the outgoing sewage or effluent is not allowed to carry with it large amount of the suspended matter (Van-Lier et al., 2008; Spellman, 2013). As these are more costly, and other cheaper sludge digestion methods are available, they are not very popular now-a-days. But for small installations they are still used with many advantages.

7.20.1. Design Considerations of Imhoff Tank The solids of sewage settling to the bottom of the sedimentation chamber through the sloping bottom walls are made to fall in the digestion chamber through an entrance slot at the lowest point of the sedimentation chamber (Figure 7.26). The slot is trapped or overlapped in such a way that the gases generated in the digestion chamber cannot enter the sedimentation chamber. The solids are digested under anaerobic decomposition and when this process is complete they can be withdrawn through the sludge pipe under hydrostatic head between the water level in the tank and the sludge outlet. All the sludge is not removed, only the lower layers which are completely decomposed are withdrawn leaving some sludge to keep the tank seeded with anaerobic bacteria. The gases formed during digestion escape through gas vents. Some solids rise to form a scum which is collected in the scum chambers. The cross wall breaks up the currents of entering sewage and serves as support to the sloping walls. The cross walls should be spaced 5 m apart in large tanks. The digestion chamber is made up of two or three inverted cones called hoppers with sides sloping to concentrate the sludge at the bottom of the hopper. The inlet and outlet may have a weir across the sedimentation chamber and a baffle extending about 40 cm below the surface.

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Fig.7.26 Details of Imhoff Tank Source: Van-Lier et al. (2008)

The detention period is usually 1.5-2.5 hours. The sedimentation chamber should not be too deep (usually not more than 3m from sewage surface to the plane of slot). The lengths are seldom more than 30 m. The length-to-width ratio should be 3:1 to 5:1. When the gases because of digestion escape through the vents, sufficient gas vent area should be provided. Otherwise lifting of scum or foaming may occur. The gas vent area should be 15-25% of the total area of the tank. The digestion chamber should have enough capacity to avoid operational troubles like foaming. Greater sludge capacities should be provided so that relatively large volume of well-digested sludge always remains in the tank. The rate of sludge digestion mainly depends on temperature. Hence greater sludge capacities may not be required where temperatures are high and sludge withdrawals are frequent. For warmer climates 0.030-0.055 m3 per capita sludge capacity is considered sufficient. The volume of the 'neutral zone' is not included in calculating the required sludge capacity. Some other design details recommended by health department are as given below: (i)

Minimum vertical distance between sludge outlet and sewage level in tank should be 1.5 m;

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(ii)

Width of the slot should be 20-25 cm;

(iii)

Overhang at slot to prevent entrance of gas to sedimentation tank should be 20-25 cm;

(iv)

Minimum slope of sludge hopper should be 30°;

(v)

Minimum diameter of sludge pipe should be 20 cm;

(vi)

Minimum vertical distance between upper sludge level and plane of slot should be 45 cm;

(vii) Total depth of tank should be about 10 m; (viii) Velocity of flow of sewage should be 30 cm/min.

7.20.2. Operation of Imhoff Tank For better efficiency and less odour, the Imhoff tank needs constant attention. The scum formed in the sedimentation chamber should be removed daily by some type of skimmer. The slot is sometimes clogged and should be cleaned. The sludge level should never rise above the lower edge of the neutral zone which can be controlled by frequent sludge withdrawals. Foaming in the gas vents accompanied by very bad odour is the common trouble. The foaming may be due to industrial wastes (acidic) or unbalanced volumes of raw and well-digested sludge. The foaming occurs in new tanks unless a mass of well-digested slurry accumulates. To avoid this, new tank may be seeded with well-digested sludge from another tank. Chronic foaming trouble can be reduced by pre-chlorination of sewage. Addition of hydrated lime through gas vents corrects the acidity of sludge and reduces foaming.

7.20.3. Merits and Demerits of Imhoff Tank As the Imhoff tanks combine the advantages of both septic tank and sedimentation tank, they are adopted for small installations requiring only preliminary treatment. They have better economy and give good results without skilled attention with minimum sludge disposal problems. The disadvantages of Imhoff tanks are their greater cost due to greater depth and their unsuitability for highly acidic sewages. Due to inadequate control over their operation, they are not suitable for large installations where separate sludge digestion tanks are preferred.

7.21. Aqua Privy The aqua privy (Figure 7.27) is based on the principle of septic tank action whereby the tendency of excreta to liquefy anaerobically when enclosed in a watertight tank is made use of. In an aqua privy, the septic tank is directly under the latrine pan and 1 to 2 liters of water are sufficient to flush. It consists of squat plate with a drop pipe of 10 cm diameter extending about 8.0 cm into it watertight tank to a point below the water level. This depth is sufficient to pierce the scum that floats on the surface of the liquid.

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Faeces and urine fall into the tank where they undergo decomposition as in the septic tank. The solids are reduced in volume to about a quarter of the faeces deposited. The effluent is led off from the tank to undergo further treatment either in the seepage pit or the subsoil absorption field. The solids remaining in the tank must be removed periodically. After several years of operation (six to eight years approximately), the digested sludge in a family size installation will occupy 40-50% of the tank's water capacity and should then be bailed out.

Fig. 7.27 Aqua Privy Source: Obeng et al. (2015)

In the construction of this type of latrine, it is important that the tank remains watertight, otherwise the liquid level may drop causing the seal to break and admit gases into the structure above. The shape of the tank may be circular or rectangular. The

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tank may be made of brick or stone masonry plastered with cement or concrete. A vent should be provided for the escape of gases into the atmosphere. The vent should be open above the roof of the dwellings. The designed capacity of the tank may be 0.028 to 0.056 m3/capita. The aqua privy has the merit of finding use in the sewage disposal of houses and dwellings where it can be located near the building. It requires only little attention and can withstand abuse. The aqua privy is permanent type of installation which is relatively simple and inexpensive. When first constructed the tank should be filled with water. The tank if properly operated can work for several years without cleaning. Aqua privies are designed for public use also. The disadvantages of aqua privy include high initial cost, requirement of operation and maintenance daily and has limited use in cold climates. The aqua privy may not be successful in rural areas where there are no organized sanitation health education services.

7.22. Chemical Toilet Chemical toilet is one of the excreta disposal methods without water carriage system. The chemical closet has very limited use under Pakistani conditions. It has a metal tank containing caustic soda solution. A seat with cover is placed directly over the tank, which is ventilated by a flue rising through the house roof. The tank is made up of copper-bearing steel capable of withstanding corrosion and has a capacity of about 500 litres per seat. A charge of 11.3 kg of caustic soda dissolved in 50 liters of water is applied to the tank for each toilet seat. The excreta deposited in the tank are liquefied and sterilized by the chemical, which also destroys all pathogens and worm eggs. The tank is usually provided with an agitator which breaks the solids and speeds their disintegration by the chemical. After several months of operation, the spent chemical and the liquefied matter are drained or removed through a drain valve in the bottom of the tank and are deposited in a suitably located leaching cesspool. The effluent from the chemical toilets can be used as fertilizer. No other wastes except human excreta should be introduced in the tank. The toilet paper should exclusively be used. If the water is thrown into the closet, the chemical solution gets diluted and the closet does not function properly. The toilet is nonodorous and suitable for use inside dwellings, isolated houses, schools, etc. It is also employed in the form of a movable commode of about 40 liter capacity on boats, aircraft, motor caravans, and other vehicles. It is expensive in initial cost and in operation. If poorly operated and maintained, which happens when the chemical is spent and not immediately replaced, there are odours and an increasing amount of floating matter over the liquid contents. Due to these reasons, chemical toilets cannot be used in rural areas at present.

7.22.1. Shallow Trench Latrine Shallow trench latrine is simply a trench dug with ordinary tools. The trench is 30 cm wide and 90-150 cm deep while its length depends on the number of users. A trench length of 3-3.5 m is necessary for every 100 people. Separate trenches should be provided for men and women. The earth from the trench should be piled up at the

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sides. The users are supposed to cover faeces with earth each time they use the latrine. However, under Pakistani conditions it is possible that rural people may not cover the faeces, and it will be necessary to post sweepers in attendance to do this work. Ablution water should be provided. The shallow trench is a rudimentary arrangement for a short period (up to one week). When the trench is filled to 30 cm below ground level, it must be covered with earth and compacted if necessary. A new trench must be dug.

7.22.2. Deep Trench Latrine Deep trench latrine is useful for camps of longer duration, from a few weeks to a few months. The trench is 1.8 to 2.5 m deep and 75-90 cm wide. Depending upon the local custom, a seat or a squatting plate is provided. A super structure is built for privacy and protection. Other requirements are the same as for shallow trench latrine. 7.22.2.1. Sludge Disposal The sludge contains the waste water from the kitchens, wastes from bath, wash water from privies and a considerable quantity of urine. The sludge does not contain night soil. In villages, the water is often disposed of from kitchens and bathrooms by means of irregular, open and unlined channels passing in front of the houses. This water flows over the katcha roads and lanes having inadequate slopes. Water is absorbed in the ground making it swampy. This endangers the nearby structures. In due course of time the ground gets saturated and the water neither gets absorbed nor flows due to the absence of regular drain. A few rural dwellings having their own source of water supply like hand-pump discharge water on the streets. The situation is further aggravated by the movements of carts and animals that creates ditches full of stagnant and dirty water. Such waterlogged area is the source of mosquito breeding. The best way of disposal of the sludge is using a soak-pit near the house after straining of the suspended matter. 7.22.2.2. Soak-Pit A soak-pit is just earth prepared for absorbing water. The absorption takes place through the sides and bottom of the pit. For the average village house a trench 3 m long. 1m wide, 1m deep at the proximal end and 1.5 m deep at the distal end will be sufficient. After excavating the earth, the trench is filled with large, irregular-shaped stones to prevent the sides of the trench caving in when wet. The irregular shape ensures plenty of crevices between the stones to hold the water until it is absorbed. At the proximal end of the trench (the end will receive the water) an empty kerosene tin or similar container with its bottom perforated is placed on the stones when they are about 20 cm from the surface of the ground (Figure 7.28). The tin is about 15 cm above the surface of the ground and 20 cm in the pit. The pit is filled with the stones until 10 cm from the surface and then covered with the old bamboo matting, old sacks or old tin sheets or failing everything several layers of old newspapers. The purpose of this is to seal off the pit at the top, to prevent earth getting in and choking the crevices between the stones, which would in time convert the pit to a solid block with no capacity to hold water. If possible the matting, tins, etc. should be tarred as they then last longer.

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Above the matting, earth is filled to ground level. The pipe issuing from the bathrooms or sink should empty into the tin. The tin should be filled with straw, dried grass or similar material which will filter off the solids, especially waste food, suspended in the water. An extremely penetrating and offensive smell can issue from particles of waste food decomposing in a soak-pit. A straw is an insurance against this, and it must be changed daily. The soaking trench of this type will absorb strained water for months or years. The dimensions can be varied, and a trench too large does not matter, but if too small, it will overflow. The height of the tin projecting above ground level is a matter of convenience. 7.22.2.3. CSV Soak-Pit The design recommended by the Centre of Science for Villages, Wardha, is slightly different. The length and width of the trench are 90.0 cm each. The depth at the proximal end is 82.5 cm and at the distal ends 97.5 cm (Figure 7.29). Fig. 7.28 Soaking Trench Source: Obeng et al. (2015)

The big boulders are used at the bottom, medium boulders in the middle and small boulders on the upper side of the trench. A layer of covering materials containing jamun sticks covered with gunny bags is prepared. Over the gunny bags another layer of jamun sticks is used. This is then covered with earthen mud. The kerosene tin is replaced by perforated bucket filled with grass. Below this, perforated earthen jar having coconut coir is used.

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Fig. 7.29 CSV Soak-Pit Source: Redwood (2004)

The big boulders are used at the bottom, medium boulders in the middle and small boulders on the upper side of the trench. A layer of covering materials containing jamun sticks covered with gunny bags is prepared. Over the gunny bags another layer of jamun sticks is used. This is then covered with earthen mud. The kerosene tin is replaced by perforated bucket filled with grass. Below this, perforated earthen jar having coconut coir is used.

7.23. CBRI Waste Water Disposal System The waste water disposal system developed at the Central Building Research Institute, Roorkee, consists of an ash-silt trap chamber and a bore hole. The soakage pit system is a small compact unit designed for individual dwelling. The whole system is covered and is below the ground level avoiding any hindrance in movement and chances of mosquito breeding. Only an auger for making the bore hole is required. The ash-silt trap chamber is rectangular. It is divided into two compartments by a 7.5 cm thick wall and is covered with a R.C.C. or reinforced brick lid. The sizes of the first compartment are 45 cm × 45 cm × 70 cm and of the second compartment 30 cm × 45 cm × 70 cm. Triangular ducts of 8 cm × 8 cm in size and

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46 cm deep are made in corners and adjacent to each other in both the compartments, diagonally opposite to the inlet. A hole is left in the partition wall 11.5 cm below the top in the duct portion to provide connection between the two ducts. The second compartment is filled with 4 cm gauge brick ballast. In the first compartment silt and ash, i.e. heavier particles flowing with waste water, settle down and floating greasy materials are trapped. The water having only colloidal and suspended particles rises through the duct of first compartment and flows to the bottom of the second compartment. The suspended and colloidal particles get stuck to the brick ballast and only clear water can flow into the bore hole for final disposal underground. When the first compartment gets filled with ash and silt, the lower mouth of the duct will be closed and water will stop flowing to the second compartment. This will cause flooding of the first compartment and back flow of water indicating that the compartment requires cleaning. The system is reactivated by removing ash and silt from the first compartment. The bore hole is made 30 cm in diameter and is deep enough to reach the first layer of sand subject to a maximum depth of 3 m. It is filled with brick aggregate. The first compartment of ash-silt trap chamber should be cleaned once in four months and the brick aggregate of the second compartment at least once in eight months to avoid chances of any failure of the bore hole.

References Bernal, M. P., Alburquerque, J. A., and Moral, R. (2009). Composting of animal manures and chemical criteria for compost maturity assessment. A review. Bioresource Technol., 100, 5444-5453. Blackman Jr, W.C. (2016). Basic hazardous waste management. CRC Press. Bond, T., and Templeton, M. R. (2011). History and future of domestic biogas plants in the developing world. Energy Sustain. Dev. 15, 347-354. Giusti, L. (2009). A review of waste management practices and their impact on human health. Waste Managem., 29, 2227-2239. Finley, S., Barrington, S., and Lyew, D. (2009). Reuse of domestic greywater for the irrigation of food crops. Water Air Soil Pollut., 199, 235-245. Harman, J., Robertson, W. D., Cherry, J. A., and Zanini, L. (1996). Impacts on a sand aquifer from an old septic system: Nitrate and phosphate. Groundwater, 34, 1105-1114. Hoornweg, D., and Bhada-Tata, P. (2012). What a waste: a global review of solid waste management. Urban development series knowledge papers, World Bank, Washington, DC, USA. Li, F., Wichmann, K., and Otterpohl, R. (2009). Review of the technological approaches for grey water treatment and reuses. Sci. Total Environ., 407, 34393449. Mahar, A., Malik, R.N., Qadir, A., Ahmed, T., Khan, Z., and Khan, M.A. (2007). Review and analysis of current solid waste management situation in urban areas of Pakistan. In: Proceedings of the International Conference on Sustainable Solid Waste Management, Vol: 8, pp. 5-7. Murtaza, G., Ghafoor, A., Qadir, M., Owens, G., Aziz, M. A., and Zia, M. H. (2010). Disposal and use of sewage on agricultural lands in Pakistan: A review. Pedosphere, 20, 23-34.

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Obeng, P. A., Oduro-Kwarteng, S., Keraita, B., Bregnhøj, H., Abaidoo, R. C., Awuah, E., and Konradsen, F. (2015). On-site sanitation systems for low-income countries: technical guidelines for groundwater. In: Impact of Water Pollution on Human Health and Environmental Sustainability. IGI Global Disseminator of Knowledge, New York, USA. Qadir, M., Wichelns, D., Raschid-Sally, L., McCornick, P. G., Drechsel, P., Bahri, A., and Minhas, P.S. (2010). The challenges of wastewater irrigation in developing countries. Agricultural Water Manage., 97, 561-568. Redwood, M. (2004). Wastewater use in urban agriculture. International Development Research Centre IDRC. Austarlia. Remais, J., Chen, L., and Seto, E. (2009). Leveraging rural energy investment for parasitic disease control: schistosome ova inactivation and energy co-benefits of anaerobic digesters in rural China. PLoS One, 4, e4856. Spellman, F.R. (2013). Handbook of water and wastewater treatment plant operations. CRC Press, Taylor and Francis Group, 6000 Broken Sound Parkway NW, Boca Raton. Van Lier, J. B., Mahmoud, N., and Zeeman, G. (2008). Anaerobic wastewater treatment. Biol. Wastewater Treat., 415-456. Van Lier, J. B., Mahmoud, N., and Zeeman, G. (2008). Anaerobic wastewater treatment. In: Biological Wastewater Treatment (Henze, M., van Loosdrecht, M.C.M., Ekama, G.A., D. Brdjanovic, IWA Publishing, London, UK. Van Loosdrecht, M. C., Nielsen, P. H., Lopez-Vazquez, C. M., and Brdjanovic, D. (2016). Experimental methods in wastewater treatment. Water Intelligence Online, 15, 9781780404752. Yaws, C. L. (2014). Transport properties of chemicals and hydrocarbons. William Andrew. FAO, Washington DC, USA.

Chapter 8

Industrial Waste Generated in Rural Areas Faizan ul Haq Khan, Abdul Nasir Awan and Shafique Anwar*

Abstract As such, there is no proper industrial setup is available in the rural areas of Pakistan. Rapidly increasing population in the rural areas, an efficient industrial setup has become inevitable. In the present scenario, life in urban areas has become very comfortable and the rural community started feeling that all those facilities must be available at their door step. Primarily different rural industries were available at far distances from village to village such as rice industry, flour mill, cotton industry, sugarcane industry etc. Now the rural community wants all these industrial facilities at their door step, because they want to harvest maximum benefits without wasting their time and extra cost on handling their products. Byproducts produced from rural industries are of great importance in nature and values. These byproducts can be used for completing different projects such as waste generated by rice industry can be used as construction material, sugarcane industrial waste (bagasse) can be used as an alternative fuel for gur making, for manufacturing of cardboard and chipboard etc. These can be used as manure for reconditioning the soils of rural areas to increase their fertility level. Keywords: Industrial waste, rice byproducts, sugarcane byproduct, tannery waste, lather byproducts, gur industry byproduct.

*

Faizan ul Haq Khan˧, Abdul Nasir Awan and Shafique Anwar Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

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Introduction

The rural areas of Pakistan are still far behind in industrial development. The growth of industries is confined only to urban areas. Some of the traditional industries like pottery, carpentry, black-smithy, oil expelling, flour-milling, rice milling, gur making, weaving garment, leather, rope making, and grain roasting still fulfill the demands of most of the rural people. The wastes available from these industries are small and do not pose any serious problem/threat of disposal. However, utilization of byproducts of a few of the important industries is described as under.

8.2.

Rice Mill Byproducts

The husk, bran, germs and broken rice are the main byproducts of rice milling industry and comprise nearly 20-25%, 5-7%, 1-2% and 2-3% of the total rice milled respectively (Shafie, 2016).

8.2.1. Rice Husk The rice husk can be used to generate power and steam. One kilogram of rice husk can generate 2.5 to 2.8 kg of steam at 11 kg cm-2 pressure and is equivalent to 0.33 kg of fuel oil. The steam can be utilized for parboiling of paddy and generation of power for the operation of rice mills. A lot of research is carried out on variety of rice and by-products of rice in the rice institute at Kala Shah Kaku. The rice husk can be used as cementing material in building construction. At International Rice Research Institute, Manila, Philippines, has developed a furnace in which rice husk can be used for heating the air for drying grains. Each 4– 6 kg of husk burnt per hour can raise the temperature of ambient air by 10°C at a flow rate of 25 m3 per min. The furnace generates sufficient heat to dry 1 ton paddy from 20% to 14% moisture content by burning the husk produced from 1 ton of paddy milled. Sodium silicate which is used in the manufacture of soaps, detergents, silica, gel, adhesives etc., can be made from rice husk ash. The ash obtained from the husk is mostly silica in highly reactive form. In this process, it is made to react with caustic alkali and the solution of sodium silicate so obtained is concentrated material. The process is simple, capital investment is low and it can be adopted by the small-scale sector in rural areas. The reaction takes place at low temperature and consequently the fuel consumption is low. The rice husk can also be used for the manufacture of cementitious binder possessing properties like Portland cement. Husk obtained from paddy hullers can be directly used but that produced in the full shell form by the rice mills should be passed through a huller or a grinding machine before use in the process. The other ingredient, lime sludge, available from sugar, acetylene, paper industry, etc. should be in dry and powdery form.

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Waste lime sludge and rice husk are dry mixed together roughly in equal amounts by weight. The required amount of water is added to the dry mix for making balls/cakes (like those of animal dung) manually. The balls are dried in open and fired on a grating base of a clamp or in a trench. Rice husk not only acts as an integral fuel but also provides in-situ silica for the lime produced during firing. The fired material obtained is a soft powder. It is ground in a ball mill to achieve sufficient fineness to increase its reactivity (Chauhan et al., 2012). This binder can be used in making ordinary concrete and concrete for sub-flooring and terracings in place of lime concrete, masonry mortar and plaster, for soil stabilization, load bearing concrete blocks and pressed and stabilized bricks etc. In Pakistan, research has been carried out to develop a technology for making chipboards by utilizing paddy husk by mixing it thoroughly with phenolformaldehyde resin and pressing the material; in hydraulic press under controlled conditions. The characteristics of the board from rice husk using this binder are given in Table 8.1. Table 8.1 Properties of Paddy Husk Particle Board Property Value Medium Density Minimum modulus of rupture (kgcm-2) 150 Tensile strength perpendicular to the plan of the board (kgcm-2) Bulk density (kgm-3) Water absorption % (24 hr in water) Thickness swelling (%) after 2 hr immersion in water

High Density 200

5

8

800

1000

30 - 35

15 - 20

5-8

0-5

Source: Chauhan et al. (2012)

8.2.2. Rice Bran Although bran is only 5-7% of the total rice milled, it is of great economic value. The rice bran is potential source of edible oil. The bran contains nearly 15-20% oil. The removal of oil from rice bran does not reduce its value as stock feed since the percentage of protein, mineral and vitamin content is increased. The defatted bran is more stable with respect to rancidity, which is a serious problem in the storage of this feed. Rice bran oil can be technically and economically refined to high quality edible oil which is a very good supplement of edible oil, resources. Rice bran oil suitable for cooking purposes is achieved after de-odourization process only, but for its use as salad oil it should go through the winterization process wherein saturated glycerides having high milling points are removed.

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Rice bran when exposed to damp atmosphere readily absorbs moisture and an enzyme present in the bran becomes very active and splits the oil into free fatty acids (FFA). The oil becomes unfit for refining and edible use. The safe limit for FFA edible oil is 2-4%. Therefore, the enzymes responsible for increase in FFA should be destroyed or inactivated. As soon as paddy is milled and rice is polished, the bran should be heated and stored. The process will not allow any increase in FFA and edible rice bran can be obtained from the stabilized bran (Issaka et al., 2015). In Pakistan, a successful technology has been developed to process for the stabilization of bran. The principle of the process lies in shifting the pH of the bran to the level where the lipase activity would be negligible. This has been achieved by using commercially available hydrochloric acid, adjusting the pH to 4.0 at this value, the activity of enzyme is nearly zero. To achieve complete inactivation of the enzyme system 40 liters of commercial concentrated hydrochloric acid is required for one tonnes of bran. The process involves spraying of hydrochloric acid on the bran in drum and mixing the lot for four minutes. Stabilization of bran by manual mixing is also possible for small lots. The potential food uses of rice bran may include bread, muffins, pan cakes, cookies, cakes, extruded snacks or breakfast cereals, coating and crusts for finger feeds or confections, spice carriers, deep fried preparations etc. De-oiled rice bran can be used for the preparation of protein concentrates.

8.3.

Gur Industry Byproducts

Bagasse is a byproduct of cane crushing industry. It is utilized for the manufacture of pulp and paper. The composition of bagasse is given in Table 8.2. Table 8.2 Composition (as per cent dry matter) and Characteristic of Bagasse Type Whole Fiber Pith

α-cellulose 36.3 41.4 33.2

Pentosans 28.2 29.2 29.8

Lignin 20.2 20.8 20.7

Ash 2.3 1.0 2.9

Misc. organic 12.8 7.6 13.4

Source: Robertson and Thorburn (2007)

Bagasse, during the cane crushing period is directly depithed and fed to the digesters while during the non-crushing period, it is partly depithed, baled and stored. Cooking of bagasse is carried out batch-wise in spherical digesters under pressure, with about 10% by weight of caustic soda. The cooking yield is around 50%. The cooked bagasse pulp is washed free of the spent liquor, screened and bleached to achieve the desired brightness (Bizzo et al., 2014). In stock preparation, the pulp is refined to develop the strength properties. The additives like alum, rosin, china-clay or talc and dyes are blended to impart the pulp, the desired properties of the end product. At this stage, extra-long fibred pulp is also blended with the bagasse pulp. The combined stock flows to the machine chest, to be fed subsequently into the head circuit of the paper machine. The flow diagram for paper from bagasse is shown in Figure 8.1.

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Fig. 8.1 Flow Diagram for Paper Making from Bagasse Source: Hoornweg and Bhada-Tata (2012)

8.4.

Byproducts of Leather Industry

The refuse of leather tanning industry consisting of scrapings of flesh, bits of hide and leather, hair etc. forms very slow-acting manure. The nitrogen content in this manure varies from 0.8-1.2%. Though leather shavings contain over 8% nitrogen, they are difficult to decompose and remain as such for a long time in the soil. A huge quantity of water is also available from village tannery which gives very bad smell. Some of tannery wastes contain lime and other chemicals such as arsenites and chromates used in tanning leather. Some of tannery wastes are toxic to the plants. Therefore, great care must be exercised in the use of tannery waste as manure. The tannery water, however, may be disposed off through soak pits of simple contraction for sanitary reasons. The tanneries available on G.T. road and in District Kasur are working for development of proper techniques to dispose off the tannery waste properly to keep the environment of the nearby areas according to the NEQS (National Environmental Quality Standards). The waste water produced because of various treatments during tanning operations can be managed under four major types of processing: vegetable tanning, chrome tanning, combined tanning (both vegetable and chrome tanning) and processing for semi-finished lather.

8.5.

Vegetable Tannery

The salt-laden waste soak liquor from the soaking process is collected separately in solar evaporation pans. The dried salt can be manually scrapped, collected and dumped suitably, wherever possible or re-used for pickling and preservation of raw hides and skins after purification.

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Composite waste water collected from various unit processes can flow into equalization-cum-settling tanks. Sludge from the settling tanks is removed and dried on sludge drying beds. Settled effluent from equalization-cum-settling tank is pumped to anaerobic lagoons followed by aerated lagoons for biological treatment. Treated effluent can be used for agricultural purpose or discharged into inland surface waters. The effluent after effective treatment may be discharged into sewers if available. Dried sludge from sludge drying beds can be used as manure or for land fill.

8.6.

Chrome Tannery

Treatment flow sheet for chrome tannery effluent is like that for vegetable tannery effluent except that the dried sludge from the chrome tanning waste should be incinerated and buried to contain leaching of metal to the ground water.

8.7.

Combined Tannery

The salt laden soak liquor is collected separately and allowed to dry in evaporation pans. Waste water from liming, pickling and chrome tanning is collected separately in the first set of equalization-cum-settling tanks. Waste water from the processes namely second and third soaking, liming, deliming, bating, vegetable tanning and finishing is collected in the second set of equalizationcum-settling tanks. Sludge from the settling tanks provided for the collection of vegetable tanning wastes can be utilized after drying as manure or for land fill. Sludge from the settling tanks provided for the collection of chrome tanning waste should be disposed off through incineration or burial. Settled effluents from all the tanks can be combined for suitable secondary treatment depending upon the volume of the effluent and mode of disposal.

8.8.

Semi-Finished Leather Processing

Waste water from various unit operations can flow into the equalization-cum-settling tanks. The settling tanks relate to a chemical dosing tank from where required dose of lime or lime with alum is added into settling tanks to neutralize the effluent. The settled effluent should be treated in aerated lagoon or oxidation ditch. Sludge from the equalization-cum-settling tanks can be disposed off properly.

8.9.

Leather Boards

Considerable quantities of vegetable and chrome tanned leather shavings and trimmings are available with village shoe makers and cobblers. This leather waste can be converted into leather boards and profitably utilized in making insoles, mid soles, stiffeners etc. in the footwear industry. Leather boards also find application in leather goods industry for making cheaper goods like cycle tool boxes, book covers, kitbags, transistor cases and hat linings. These can also be used for making gaskets

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and washers. The process of making leather boards involves the sorting out of trimmings and shavings and their dry grinding. The ground leather fibers are collected in a chamber through cyclone separator. Knots are removed and the de-fibred leather is further ground by adding water and made into a pulp. The leather slurry or pulp is mixed with soda or ammonia to adjust the pH, wetting agent, sulphate oil, stabilized rubber latex, aluminum sulphate and preservative. The binder rubber is precipitated around each leather fiber by means of aluminum sulphate. The coagulated pulp is pumped to storage tanks and drawn for sheet making. The wet boards after filtration are stacked in a hydraulic press and pressed at a pressure of 350 to 400 kg cm-2. The size of the board depends on the size of the hydraulic press. After drying a little, the boards are pressed in semi-wet condition again and finally dried in a drying chamber. The dried boards are calendared and the edges trimmed in a board cutter Figure 8.2. If coloured boards are required for making goods, they are also finished like leather.

Fig. 8.2 Flow Diagram for Leather Boards Source: Joseph and Nithya (2009)

8.10. Minor Rural Industrial Waste Large quantities of ash are available from pottery, gur making, grain roasting and black-smithy. The manurial value of these ashes depends upon the fuel used in the processes. The manurial value of ash available from typical pottery, gur making and black-smithy industry is given in Table 8.3. However, these ashes need to be evaluated under actual field conditions for their effect on the yield of various crops. The broken earthen wares thrown by village potters may serve as a material for rural roads. The use of cakes available from oil expelling as animal feed or manure is well established. However, the rags available from garment enterprise, though small in quantity, may be utilized for the preparation of pulp and paper.

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Table 8.3 Manurial Value of Ash available from Typical Pottery, Gur Making and Black-Smithy Industry Manurial component N P 2O K 2O

Pottery 0.05 0.78 0.66

Value (%) Gur making 0.12 1.00 2.80

Black-smithy 0.43 0.45 0.53

Source: Coutand et al. (2008)

The process of preparing specialty papers from rags consists of digesting the sorted and dusted rags in a digester with alkali, washing it free of alkali after digestion and reducing it to half-stuff in a beater. The half-stuff is bleached in wooden or cement container and then beaten to pulp. Required amount of colour, sizing chemicals, loading materials are added in the beater. The resulting pulp is diluted and passed through strainer. It is then lifted into paper sheets which are hidden, passed, peeled, dried and surface sized. After maturing, the sheets are calendared, sorted, cut and packed. The specialty paper may be used as filter pads and papers, drawing paper, decorative paper, bond and cover papers, album papers etc. The chips available from wood working are presently used for fuel purposes. Nevertheless, these wooden chips and dust need to be compacted to increase their heat utilization efficiency. Saw dust can be used to manufacture active carbon. The active carbons are used for de-colourization and absorption of gas and vapour. The process for the preparation of de-colourizing type active carbon consists of soaking of saw dust in solution of surface-active agent, carbonization of the chemically treated sawdust, withdrawal of the char in absence of air, crushing and treatment with acid solution till the attainment of a particular pH (Jayathilakan, 2012). For the preparation of gas/vapour absorption type active carbon, the product thus obtained is further blended with a binder and pelleted to give the requisite size. The pellets are then subjected to steam activation at an optimum temperature.

References Bizzo, W. A., Lenço, P. C., Carvalho, D. J., and Veiga, J. P. S. (2014). The generation of residual biomass during the production of bio-ethanol from sugarcane, its characterization and its use in energy production. Renew. Sustain. Energy Rev., 29, 589-603. Coutand, M., Cyr, M., Deydier, E., Guilet, R., and Clastres, P. (2008). Characteristics of industrial and laboratory meat and bone meal ashes and their potential applications. J. Haz. Mat., 150(3), 522-532. Chauhan, B. S., Mahajan, G., Sardana, V., Timsina, J., and Jat, M. L. (2012). Productivity and sustainability of the rice-wheat cropping system in the IndoGangetic Plains of the Indian subcontinent: problems, opportunities, and strategies. Adv. Agron., 117, 315-369. Hoornweg, D., and Bhada-Tata, P. (2012). What a waste: a global review of solid waste management. Urban Dev. Ser. Knowledge Pap., 15, 1-98.

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Issaka, J. H., Alemawor, F., and Dzogbefia, V. P. (2013). Bioconversion impact of pleurotus ostreatus on the value of rice and groundnut by-products as feed resources. Research in Biotechnol., 4:1-12. Jayathilakan, K., Sultana, K., Radhakrishna, K., and Bawa, A.S. (2012). Utilization of byproducts and waste materials from meat, poultry and fish processing industries: a review. J. Food Sci. Technol., 49, 278-293. Joseph, K., and Nithya, N. (2009). Material flows in the life cycle of leather. J. Cleaner Prod., 17, 676-682. Robertson, F. A., and Thorburn, P. J. (2007). Management of sugarcane harvest residues: consequences for soil carbon and nitrogen. Soil Res., 45, 13-23. Shafie, S. M. (2016). A review on paddy residue based power generation: Energy, environment and economic perspective. Renew. Sustain. Energy Rev., 59, 10891100.

Chapter 9

Scope of Biomass Energy in Pakistan Faizan ul Haq Khan, Abdul Nasir Awan and Hafiz Muhammad Safdar Khan*

Abstract Since the ancient time, human have harnessed biofuel derived energy when people use to burn wood as fuel. Even now a days, still biomass is used as a source of fuel at domestic level in many developing countries. Biomass is biologically based fuel having carbon, hydrogen and oxygen, includes: rural and urban solid waste. The largest source of energy from wood is a waste product from process of the pulp, paper and chip board industry on one hand and on the other hand plants and animal waste which can be converted into fiber or other industrial chemical including, biofuels. Plant energy is produced by crops, especially, grown for fuel purposes. The main contributors of waste energy are municipal solid waste, manufacturing waste and landfill gas. Biomass can be converted to other usable form of energy like, compacted briquettes, methane gas, or transformation fuel, like ethanol and biodiesel. Corn and sugarcane on fermentation yield transformation fuel (ethanol). Biomass is always considered as healthy fuel which is environmental friendly. Use of biomass can reduce forest management, help mitigate climate change, reduce risk to life and property, especially for rural communities because this is directly related with agricultural and forestry land.

*

Faizan ul Haq Khan˧, Abdul Nasir Awan and Hafiz Muhammad Safdar Khan Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s E-mail: [email protected] Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Abdul Nasir Awan and Faizan ul Haq Khan University of Agriculture, Faisalabad, Pakistan.

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Keywords: Biomass, biological fuels, paper pulp, compacted briquettes, plant energy, fermentation fuel, transformation fuel, ethanol, forest land fuel, chipboard industry.

9.1.

Introduction

Historically, humans have harnessed biomass-derived energy since the time when people began burning wood to make fire. Even today, biomass is the only source of fuel for domestic use in many developing countries. Biomass is all biologicallyproduced matter based in carbon, hydrogen and oxygen. Wood remains the largest biomass energy source today; examples include forest residues (such as dead trees, branches and tree stumps), yard clippings, wood chips and even municipal solid waste. Harvested wood may be used directly as a fuel or collected from wood waste streams. The largest source of energy from wood is pulping liquor or "black liquor," a waste product from processes of the pulp, paper and paperboard industry. In the second sense, biomass includes plant or animal matter that can be converted into fibers or other industrial chemicals, including biofuels. Industrial biomass can be grown from numerous types of plants, including switch grass, hemp, corn, poplar, willow, sorghum, sugarcane, bamboo, and a variety of tree species, ranging from eucalyptus to oil palm (palm oil) (Kelly-Yong et al., 2007). Plant energy is produced by crops specifically grown for use as fuel that offer high biomass output per hectare with low input energy (Shuit et al., 2009). The main contributors of waste energy are municipal solid waste, manufacturing waste, and landfill gas. Biomass can be converted to other usable forms of energy like, compacted briquettes, methane gas or transportation fuels like ethanol and biodiesel. Rotting garbage, and agricultural and human waste, all release methane gas, also called landfill gas or biogas. Crops such as corn and sugar cane can be fermented to produce the transportation fuel ethanol. Biomass for energy, especially biofuels, has positive attributes that contribute to a healthy environment and economy. Biomass utilization can reduce forest management costs, help mitigate climate change, reduce risks to life and property, and help provide a secure, competitive energy source. Shifting to a homegrown, renewable energy economy provides opportunities for growth and expansion, especially for rural communities as these renewable feedstock’s are directly connected to the land, primarily agricultural and forestry lands. With a constant supply of waste from construction and demolition activities, to wood not used in papermaking, to municipal solid waste green energy production can continue indefinitely.

9.1.1. Biomass Energy Biomass is fuel that is developed from organic materials, a renewable and sustainable source of energy used to create electricity or other forms of power. Some examples of materials that make up biomass fuels are scrap lumber, forest debris, certain crops, manure and some types of waste residues (Saxena et al., 2009).

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Biomass is organic matter derived from living, or recently living organisms. Biomass can be used as a source of energy and it most often refers to plants or plant-based materials which are not used for food or feed, and are specifically called lignocelluloses biomass. Biomass is a plant attribute that is time consuming and difficult to measure or estimate, but easy to interpret. Biomass is regarded as an important indicator of ecological and management processes in the vegetation (Stout, 2012).

9.1.2.

Objectives of biomass energy

(i) To study alternative sources of energy in Pakistan. (ii) To reduce the waste resources of the country. (iii) To turn waste into clean energy.

9.1.3.

Goals of biomass energy

(i) Enhance national security. (ii) Benefit the environment. (iii) Balance trade deficits. (iv) Bolster rural economics.

9.2.

Biomass Power

Biomass power is carbon neutral electricity generated from renewable organic waste that would otherwise be dumped in landfills, openly burned, or left as fodder for forest fires. When burned, the energy in biomass is released as heat. If you have a fireplace, you already are participating in the use of biomass as the wood you burn in it is a biomass fuel (Huber, 2006). In biomass power plants, wood waste or other waste is burned to produce steam that runs a turbine to make electricity, or that provides heat to industries and homes. Fortunately, new technologies including pollution controls and combustion engineering have advanced to the point that any emissions from burning biomass in industrial facilities are generally less than emissions produced when using fossil fuels (coal, natural gas, oil).

9.2.1. Biomass as a source of energy Biomass is a renewable source of fuel to produce energy because: (i)

Waste residues will always exist in terms of scrap wood, mill residuals and forest resources.

(ii)

Properly managed forests will always have more trees, and we will always have crops and the residual biological matter from those crops.

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As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods which are classified as: thermal, chemical, and biochemical methods (Saxena et al., 2009). There are several aspects to energy and biomass that are important attributes to set the stage for discussions: (i) Creating transportation fuels from biomass is technically and politically possible. (ii) Using fuels from biomass is the only feasible, renewable, mass transportation fuel alternative for the short- to mid-term. (iii) Being “home grown from our lands” provides improved rural economic opportunities now and into the future. (iv) Having our own conversion facilities in a “new industry” improves energy security, national security and Pakistan’s economic health. (v) Having the needed feedstock supply is dependent on Pakistan’s working farms and forests.

9.3.

Biomass Potential and Resources on a Global Scale

Potential for more efficient use of biomass, bioenergy is increasingly becoming a prerequisite for achieving emission reduction targets for greenhouse gases and improving the security of energy supply worldwide. Many studies have assessed the potential to increase bioenergy, by assuming an overall increase in biomass production (up to 500 EJ by 2050). The potential increase from an analysis of current and future efficiencies in using agricultural crops and residues, and wood for bioenergy, considering current biomass production levels, and the lifecycle phases of biomass products and waste flows (Stout, 2012). The energy content of agricultural crops including residues produced worldwide is estimated at about 200 EJ, with grass and rangeland producing about 115 EJ, both mainly delivering inputs to the human food system. The net input is estimated at about 100 EJ yr-1, of which about 18 EJ originates from the livestock system. Only a small proportion of the primary production is used to produce energy and materials, and comes mostly from crops, such as sugarcane and corn. Only 5% of the energy content of crops and residues is used for bioenergy and materials (420 Mt about 11 EJ). However, use of unused and burned crop residues would add about 24 EJ for bioenergy and materials production. This would increase the proportion from 5% to 17% of the energy content from crops and residues used in bioenergy and material production. The assumptions included sustainable soil carbon management (roughly half of the aboveground carbon remains on the soil). Other potential energy sources are improved use of waste flows from industrial processes and consumption, and would provide an additional about 21 EJ, adding

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about 56 EJ or 18% of the energy content of the total agricultural production worldwide (crops, residues and grasslands). Analysis of the wood cycle indicated that about 2700 Mt yr-1 or about 49 EJ yr-1 annually is used as fuel wood. This is considerably more than used for other purposes, such as timber products and paper (965 Mt yr-1 or 17 EJ yr-1) and forest residues (average 960 Mt or about 17 EJ). Nevertheless, there is potential to increase the availability of wooded biomass by using current flows more efficiently, even when sustainability concerns are considered. This can be done by using a part of the primary forest residues left in the forest (globally about 17 EJ yr-1). Furthermore, about 100 Mt or about 2 EJ yr-1 of wooded products end up in landfill but are potentially useable for bioenergy. This quantity could increase considerably in the coming decades (2 to 10 EJ) because the stock of timber products is increasing (about 15 EJ is produced and about 7 EJ is waste). The potential for bioenergy can be increased by 63 EJ yr-1 by using current flows more efficiently through optimized collection and conversion and would more than double current global bioenergy supply. However, crucial to utilizing this additional potential biomass source is whether it can be collected and transported to meet geographical differences in supply and demand, and to enable large-scale processing in combination with carbon capture and storage, and reuse. There is potential crop and residue for biomass worldwide, with largest wood potential in developing countries.

9.4.

Biomass Potential in Asian Countries

Table 9.1 shows the potential of different bio-products as a sole aource of biomass in Pakistan, in comparison to some neighboring Asian countries. Table 9.1 Biomass saving potential in neighboring countries (million tons per year) Country China India Nepal Pakistan Sri Lanka

Fuelwood 51.59 69.50 3.10 17.51 2.61

Source: Zuberi et al. (2015)

Types of Biomass Agricultural residue Animal dung 77.21 2.93 20.88 28.56 1.23 0.75 7.30 8.31 0.46 -

Charcoal 0.03 0.49 0.00 0.00 -

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9.5.

Biomass Potential in Pakistan from Different Sources

Approximately 225,000 tons of crop residue and over 1 million tons of animal manure are produced daily in Pakistan. 54,888 tons of waste generated daily (Pakistan Bureau of Statics, 2011). Pakistan produces huge amount of municipal waste (Karachi 9,000 tons per day and other cities about 2,000 to 6,000 tons per day) and agriculture waste in the form of bagasse, cotton sticks and rice husk. Converting this waste to energy can generate upto 3,000 MW of power. Pakistan offers lucrative opportunities in this sector in which several projects are already under preparation (Rapid Assessment and Gap Analysis Pakistan, 2014). Potential waste/low-cost substrates in Pakistan is characterized with large agricultural and livestock sector and resultantly copious quantities of agriculture and crop residues such as rice husk, wheat straw, cane trash, cotton sticks, bagasse, municipal solid waste, animal residue and poultry litter are produced whose disposal is a big challenge. Annual production of various crops and their residue availability in Pakistan. There are three main sources of biomass in Pakistan. 1) Crop Residues 2) Animals Waste 3) Municipal Solid Waste

9.6.

Crop Residues for Bio-energy

The following Table 9.2 shows the annual production of various crops in Pakistan and their residue types; Table 9.2 - Annual production of various crops and their residue types Major crop

Annual production (tons)

Sugarcane

49,373

Dry chilly

1877

Stalks

Rice

6883

Husks, Straws, Stalks

Wheat

23,864

Cotton

3000

Maize

296

Barley

82

Bajra

470

Source: Manzoor et al. (2015)

Residue Bagasse, leaves and tops

Pod, Stalks Boll shell, Husk, Stalks Cobs, Stalks Stalks Cobs, Husks, Stalks

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These include crop leftovers after harvesting, a potential source of fuel for power generation. The main agricultural residues available in the country are: (i) Wheat straw: It is the main source of animal fodder and 10% can safely be considered as a source of fuel to generate power. (ii) Sugarcane trash: The waste of sugarcane crop which is left in the field, part of this quantity is used for cooking purposes and remaining burned by the farmers in the field. Sugarcane trash (10% of the Sugar cane crop), a potent source to produce power, is available in substantial quantities. (iii) Cotton sticks and other plant residues of cotton crop: These are also a left over in field, part of this quantity is used for cooking purposes, some quantity is lifted by the Brick kiln users, 30% is excess and can be used as a biomass source. (iv) Maize stalks: After removing the cobs from plants, 80% stalks left standing in field are harvested for feeding the animals or dried for home cooking and the remaining 20% is burnt by the farmers in the field which can easily be used for power generation. (v) Paddy straw: About 80% is used as a source of fuel in the brick kilns and as cattle feed. The remaining 20% excess is normally burnt by the farmers in the field which has bad impact on the environment, therefore, can be made available for power generation. 9.6.1.1. Wheat straw for bio-energy Wheat straw is generated after harvesting manually or mechanically by reaper or combine harvester. It is the main source of animal fodder, however, 10% can safely be considered as a source of fuel to generate power. Wheat grains are separated by mechanical thresher or by combine harvester and the straw is left in the field. About 70-75% is collected by farmers to be used as feed for animals and the remaining about 10% is left in the field which is either buried in the soil by tillage implements or burnt as such to prepare the land for seeding the next crop. The burning causes environmental pollution; therefore, the extra may be collected and used for bioenergy production (Table 9.3). The straw to grain ratio is about 1:1. 9.6.1.2. Sugarcane trash for bio-energy Sugarcane trash is generated through growing sugar cane crop which is one of the major crops in Pakistan. Sugarcane crop grown in the country is mainly used for the manufacture of refined sugar in sufficient quantities to fulfill the indigenous requirements of the country. Sugarcane tops and trash constitute 20% and 10% respectively. Cane tops are used as cattle fodder and are taken away by the farmers to feed their dairy animals. Leaving aside wastages, 9% cane trash has been considered as available biomass for power. Knowing the calorific value of cane trash, 14 GJ per ton, power generating potential of sugarcane trash available in Pakistan for four years have been calculated and presented in Table 9.4.

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9.6.1.3. Cotton Sticks for bio-energy Cotton is the other main cash crop. It is the main source of raw material to the local textile industry; the lint cotton is also a significant export item. During 2010-11, the crop was cultivated on an area of 8.67 hectares. Cotton crop production during various years has been given in Table 9.5. The ratio of plant waste to cotton is normally 3:1. From the waste a portion is used by the farmers as cooking fuel, some is lifted by the brick kiln operators and the remaining substantial quantity is available for use as fuel for power. Knowing the calorific value of cotton sticks, 18 GJ per ton, the power potential from cotton sticks for different years has been calculated and presented in Table 9.5.

Table 9.3 Power generating potential of wheat straw available in Pakistan Year

Wheat production (Ton)

Wheat straw production (Ton)

Wheat straw available for bioenergy, 10% of total (Ton)

Thermal Energy in wheat straw (GJ) [at 14 GJt-1]

Power Potential wheat straw (GWh)

2006-07 23,294,700 23,294,700

2,329,470

32,612,580

9059

2007-08 20,958,800 20,958,800

2,095,880

29,342,320

8151

2008-09 24,033,000 24,033,000

2,403,300

33,646,200

9346

2009-10 23,310,800 23,310,800

2,331,080

32,635,120

9065

2010-11 25,213,800 25,213,800

2,521,380

35,299,320

9805

2011-12 23,473,000 23,473,000

2,347,300

32,862,200

9128

*1-GWh (Giga watt hour) =3600 GJ Source: Pakistan Bureau of Statics (2013-14)

Table 9.4 Power generating potential of sugar cane trash available in Pakistan Sugar Production (Ton)

Sugarcane Trash (Ton)

Thermal Energy in Cane Trash (GJ) [at 14 GJt-1]

Power potential Sugarcane trash (GWh)

2006-07

54,741,600

4,926,744

68,974,416

19,160

2007-08

63,920,000

5,752,800

80,539,200

22,372

2008-09

50,045,000

4,504,050

63,056,700

17,516

2009-10

49,372,900

4,443,561

62,209,854

17,281

2010-11

55308500

4,977,765

69,688,710

19,358

2011-12

58,038,000

5,223,420

73,127,880

20,313

Year

*1-GWh=3600 GJ

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Source: Pakistan Bureau of Statics (2013-14)

9.6.1.4. Maize stalks for bio-energy Maize crop is among the major cash crops of the country. For the remaining 20% leftover maize stalks in the field the power potential has been determined and tabulated in Table 9.6. 9.6.1.5. Paddy straw for bio-energy Paddy production for few years has been presented in Table 9.7. Paddy plant grain to straw ratio is about 20:80. After consumption of 80% straw as a source of fuel in the brick kilns and as cattle feed, the power generation capacity of remaining 20% excess has been determined and tabulated in Table 9.7.

Table 9.5 Cotton yield and power potential from cotton sticks Year

Cotton Production (Bales)

Crop Production (Tons)

Cotton Stalks Production* (Tons)

Cotton Stalks Available for Power Generation** (Tons)

Thermal Power Energy in Potential of Cotton Sticks cotton (GJ) sticks -1 [at 18 GJt ] (GWh)

2006-07 12,856,200

2,186,711

6,560,133

1,640,033

29,520,594

8,200

2007-08 11,655,100

1,982,416

5,947,248

1,486,812

26,762,616

7,434

2008-09 11,819,000

2,010,294

6,030,882

1,507,721

27,138,978

7,539

2009-10 12,913,400

2,196,440

6,589,320

1,647,330

29,651,940

8,237

2010-11 11,460,100

1,966,257

5,898,771

1,474,693

26,544,474

7,373

2011-12 13,595,000

2,312,373

6,937,120

1,734,280

31,217,045

8,671

* Cotton stalks is one third of cotton crop production ** Cotton stalks available for power generation is one forth of total cotton stalks production Source: Pakistan Bureau of Statics (2013-14)

Table 9.6 Maize yield and power potential from maize sticks Year

Maize production (Ton)

Total crop biomass (Ton)

2006-07

3,088,000

4,632,000

2007-08

3,605,000

2008-09

Available Biomass 20% of total (Ton)

Thermal Energy (GT) [at 13 GJt-1]

Power Potential (GWh)

926,400

12,43,200

3,345

5,407,500

1,081,500

140,59,500

3,905

3,593,000

5,389,500

1,077,900

140,12,700

3,892

2009-10

3,261,000

4,891,500

978,300

127,17,900

3,533

2010-11

3,707,000

5,560,500

1,112,100

144,57,300

4,016

208 2011-12

F.H. Khan, A.N. Awan & H.M.S. Khan 4,271,000

6,406,500

1,281,300

166,56,900

4,627

Source: Pakistan Bureau of Statics (2013-14)

9.6.1.6. Summary of total power from biomass The comparison of potential or theoretical figures with the total power presently being generated has been presented in Table 9.8. 9.6.1.7. Comparison of potential biomass power with total power presently being generated Table 9.9, dipicts that if the biomass potential of Pakistan had been generated, it would had easily exceeded the total power generated in the country and became a substitute at a very cheaper rate for the imported and expensive furnace oil and natural gas required for energy generation.

Table 9.7 Paddy yield and power potential from paddy straw Year

Paddy production (Ton)

Total Crop biomass (Ton)

Available Biomass Thermal Energy 20% of total, (Ton) (GT) [at 11 GJt-1]

Power Potential (GWh)

2006-07

5,438,000

21,752,000

4,350,400

47,854,400

13,293

2007-08

5,563,000

22,252,000

4,450,400

48,954,400

13,598

2008-09

6,592,000

26,368,000

5,273,600

58,009,600

16,114

2009-10

6,883,000

27,532,000

5,506,400

60,570,400

16,825

2010-11

4,823,000

19,292,000

3,858,400

42,442,400

11,790

2011-12

6,160,000

24,640,000

4,928,000

54,208,000

15,058

Source: Pakistan Bureau of Statics (2013-14)

Table 9.8 Summary of total Power from biomass Year

Power Power Power Potenti Potential from al SugarCotton Wheat cane trash sticks straw (GWh) (GWh) (GWh)

Power Power Potential Potential from from paddy maize straw stalk (GWh) (GWh)

Power from Dairy Biogas (GWh)

Power From MSW at 2% increase per year (GWh)

Total Biomass Power available (GWh)

2006-07

9,059

19,160

8,200

13,293

3,345

11,486

13,594

78,137

2007-08

8,151

22,372

7,434

13,598

3,905

11,879

13,859

81,198

2008-09

9,346

17,516

7,539

16,114

3,892

12,286

14,129

80,822

2009-10

9,065

17,281

8,237

16,825

3,533

12,439

14,405

81,785

2010-11

9,805

19,358

7,373

11,790

4,016

13,141

14,686

80,169

9 Scope of Biomass Energy in Pakistan 2011-12

9,128

20,313

8,671

15,058

209 4,627

13,670

14,972

86,439

Source: Pakistan Bureau of Statics (2013-14)

Table 9.9 Comparison of potential biomass power with total power presently being generated Year

Power generated in Pakistan GWh

Biomass Potential of Pakistan GWh

Excess Biomass Power than Power Generated GWh

Excess biomass power potential %

2007-08

72,770

81,198

8,428

12

2008-09

69,659

80,822

11,163

16

2009-10

73,561

81,785

8,224

11

2010-11

73,806

80,169

6,363

9

Source: Pakistan Bureau of Statics (2013-14)

9.6.2. Energy from farm animals Dairy animals wise Pakistan stands fourth in the world in milk production, its indigenous production of milk stands at around 4 billion liters per year. The cattle and dairy population is also substantial and could be considered for prospecting energy from the manure from the dairy animals and cattle. The technology for extracting energy from cattle and dairy animals is through generation of biogas from the manure, this technology is well introduced in Pakistan and its use will not pose any barriers. The additional advantage for power from manure is the organic compost and slurry which can subsequently use in the fields as a rich source of fertilizer. This results in additional revenues at significant levels improving the profitability of the dairy farmers and the power operators. The quantity of biogas in any feedstock is dependent on the organic content of the feedstock, the average organic content of cattle and buffalo manure is 12%. Table 9.10 gives the energy potential from animal manure. Table 9.10 Energy potential from animals manure Year

Total Animal Manure Produced Population tons per year (Cattle + (at 10 kg per Buffalo) animal per day)

Collectable Manure Produced tons per year (50% of total)

Biogas (m3) [at 50 m3t-1 Manure]

Thermal energy Biogas Power in Biogas (GJ) Potential (GWh) [at 22 MJm-3] [at 8.14 kWhm-3]

2006-07 58820000

214693000

107346500 5367325000 118081150

11486

2007-08 60830000

222029500

111014750 5550737500 122116225

11879

2008-09 62912000

229628800

114814400 5740720000 126295840

12286

2009-10 63698000

232497700

116248850 5812442500 127873735

12439

2010-11 67294000

245623100

122811550 6140577500 135092705

13141

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2011-12 70000000

255500000

127750000 6387500000 140525000

13670

Source: Pakistan Bureau of Statics (2013-14)

9.6.3. Energy from Municipal Solid Waste Municipal Solid Waste (MSW) is another feedstock which is available in substantial quantities. The quantities generated in major city centers of Pakistan almost 7,121,626 tons per year. The calorific values of municipal solid waste determined in laboratories as per different classifications are given in Table 9.11. Taking an average calorific value of MSW = 6.872 MJkg-1 the thermal energy and power potential available in the MSW generated in the major urban centers of Pakistan is 13594 GWh per year [(6.872 x 7121626) / 3600]. To obtain an annual value for 4 years it has been assumed that the generation rate of MSW will be directly proportional to the population growth rate which is 1.95 % per annum (Govt of Pakistan, 2014). In the final analysis narrated in Table 9.12, the increase in MSW based power potential has also been incremented at this rate.

Table 9.11 Calorific values of municipal solid waste Sr. No. Area Classification

Moisture, % Calorific Value, MJkg-1

1

High Income Residential area

60

7.27

2

Medium Income Residential area

63

6.98

3

Low Income Residential Area

67

6.25

4

Commercial Area

64

6.67

5

Industrial Area

61

7.19

-1

Average Calorific Value, MJkg

6.87

Power potential = (6.872 x 7121626) / 3600 = 13594 GWhyr-1 Source: Franjo et al. (1992), Ozbay et al. (2013)

Table 9.12 Increase in MSW based power potential Year 2007-08

Power available from MSW (GWh per year) 13594

2008-09

13859

2009-10

14129

2010-11

14405

2011-12

14686

2012-13

14972

9 Scope of Biomass Energy in Pakistan 2013-14

211 15264

Source: Ozbay et al. (2013)

9.7.

Utilization of Biomass

By means of transferring, biomass can be converted to useful thermal energy, electricity and fuels for power (LIU et al., 2011). Some of main converting methods are: direct combustion, gasification and densification of biomass.

9.7.1. Direct combustion Combustion is the most common and traditional way to produce heat from biomass. In developing countries, the thermal efficiency of direct biomass combustion is 10% - 15% generally. The stove is composed of a combustion chamber, fire fencing ring, smoke circulation passage, chimney, stove door, grate and air inlet. The key design points are to increase the intensity of thermal radiation and reflection in the combustion chamber and reduce the loss of complete combustion in the inner stove and the thermal loss of smoke. Some advanced European countries adopt high efficiency combustion equipment such as sulphurized-bed combustion equipment. In the equipment, wood is cut into small pieces which then cross the sulphurized bed in a very short time. After combustion, the incompletely burned wood pieces are returned to the sulphurized bed from the smoke exhaust system (Stout, 2012). The commercialized small- and middle-sized boilers developed by these countries take wood and residues as fuel. Their efficiencies can reach 50% - 60%.

9.7.2. Gasification of biomass Pyrolyzing gasification of biomass is one of the optimum biomass utilization technologies. In gasification equipment, biomass is transferred to high-grade combustible gas through thermal chemical action at high temperature. The gas can be used for drying, heating, thermal insulation and electricity generation (LIU et al., 2011). Until now, practical biomass gasification equipment takes air as its gasification medium. Despite the low heat value, this kind of gasification stove is characterized by its simple structure and by the fact that it is convenient to operate. A brief and detailed description regarding gasification of biomass have been already discussed previously, in Chapter 4.

9.7.3. Densification 9.7.3.1. Briquetting technology Briquetting biomass technologies without Binder briquetting machines include technology-driven piston and screw-press. In screw press biomass technology is continuously extruded by a screw through a conical nut, which is externally heated

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to reduce friction. The outer surface of the tile obtained through this technology is overdone and has a hole in the center. With piston-biomass technology press is drilled into a mold from a high-pressure reciprocating piston. The briquettes produced by this technology have been burnt outer layer or the center hole. In both the piston screw press technology and application of high pressure increases the temperature of the lignin present in biomass in the form of fluid which acts as a binder. In this work, attention is focused on the technology, which is not commercially available in Pakistan.

9.8.

Biomass and Environment

There are several aspects to biomass and the environment: (i) Removing excessive levels of forest biomass can reduce fire risk which results in improved air quality and reduced greenhouse gas emissions. (ii) Managing biomass can improve productivity and improve forest health and habitat. (iii) Using biomass in bio-based products or for bioenergy can provide CO2 offsets and reduce greenhouse gases and air pollutants. (iv) Ensuring sustainable production systems that protect and enhance the environment is a hurdle for transitioning the country to bio-based, renewable fuels in sufficient quantities to significantly reduce fuel imports and benefit our economy. (v) Maintaining critical ecosystem services is dependent on maintaining America’s working farms and forests.

9.9.

Biomass and Economy

There are several aspects to the role of managing biomass in our forests and creating a bio-based economy: (i) The high costs of removing excessive biomass can be reduced or reversed through productive use of biomass. (ii) Reducing biomass can provide tangible and intangible values to landowners and the general public. (iii) Technical advances are still needed to reduce costs for feedstock production and conversion to biofuels and other products. (iv) Creating jobs in rural American and keeping our forest-based infrastructure can be an outcome of the bio-based revolution. (v) Competing successfully in the global marketplace is an important aspect of a future green economy.

9 Scope of Biomass Energy in Pakistan

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References Govt. of Pakistan (2014). Economic Survey of Pakistan 2013-14. Ministry of Finance, Government of Pakistan, Pakistan Franjo, C. F., Ledo, J. P., Rodriguez Anon, J. A., and Regueira, L. N. (1992). Calorific value of municipal solid waste. Environ. Technol., 13, 1085-1089. Huber, G. W., Iborra, S., and Corma, A. (2006). Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. Chem. Rev., 106, 40444098. Kelly-Yong, T. L., Lee, K. T., Mohamed, A. R., and Bhatia, S. (2007). Potential of hydrogen from oil palm biomass as a source of renewable energy worldwide. Energy Policy, 35, 5692-5701. LIU, Y. K., Sun, Q. F., LI, D. M., and Chen, Z. Q. (2011). Current status and prospect of the utilization of biomass wastes [J]. Chem. Engineer, 3, 28-30. Manzoor, M., Tabssum, F., Javaid, H., and Qazi, J.I. (2015). Lucrative future of microalgal biofuels in Pakistan: a review. Int. J. Energy Enviro. Engg., 6, 393403. Ozbay, I., and Durmusoglu, E. (2013). Energy content of municipal solid waste bales. Waste Manage. Res., 31:674-783 Pakistan Bureau of Statics, (2013-14). Statistics Division, Ministry of Finance and Economic Affairs, Islamabad, Government of Pakistan. Pakistan Bureau of Statics, (2011). Statistics Division, Ministry of Finance and Economic Affairs, Islamabad, Government of Pakistan. Rapid Assessment and Gap Analysis, Pakistan. (2014). Sustainable energy for all. Governamnet of Pakistan. https://www.se4all.org Saxena, R. C., Adhikari, D. K., and Goyal, H. B. (2009). Biomass-based energy fuel through biochemical routes: a review. Renew. Sustain. Energy Rev., 13, 167178. Shuit, S. H., Tan, K. T., Lee, K. T., and Kamaruddin, A. H. (2009). Oil palm biomass as a sustainable energy source: a Malaysian case study. Energy, 34, 1225-1235. Stout, B. A. (2012). Handbook of Energy for World Agriculture. Elsevier Science, New York, USA. ISBN. Zuberi, M. J. S., Torkmahalleh, M. A., and Ali, S. H. (2015). A comparative study of biomass resources utilization for power generation and transportation in Pakistan. Int. J. Hydrogen Energy, 40, 11154-11160.

Index Absorption Field, 22 Activated Sludge, 19 Aeration Tank, 19 Aerobic Digestion, 20 Airborne Dust, 149 Anaerobic Digestion, 21 Anaerobic Fermentation, 65 Animal Excreta, 82 Animal Waste By-Products, 121 Disposal, 89 Energy Generation, 97 Methods of processing, 119 Utilization of Fallen Animals, 121 Aqua Privy, 180 Ashes, 19 Bagasse, 192 Characteristic, 192 Composition, 192 Paper Making, 193 Beccari Process, 70 Biodegradation Predictability, 100 Bio-Energy, 204 Crop Residues, 204 Biogas, 97 Biogas Production Factors, 100 Chemical Properties, 97 Equivalenance, 99 Mechanical Power, 115 Physical Properties, 97 Quantity of Biogas, 66 Theory of Biogas Production, 99 Uses, 98 Biogas Plant, 103 Advantages, 114 Chinese Biogas Appliances, 115 Cleaning, 114 Fixed Dome Biogas Plant, 109 Movable Gas Holder Type, 104

Operation, 114 Biogas Pressure Determination, 110 Biological Digestion, 155 Biomass, 49 Biomass Conversion System, 49 Densification, 211 Economy, 212 Environment, 211 Gasification, 211 Liquid Fuel Production, 62 Potential, 202, 203 Potential in Pakistan, 203 Resources, 202 Source of Energy, 201 Total Power, 207 Utilization, 210 Biomass Energy, 200 Goals, 201 Objectives, 201 Biomass Power, 201 Comparison, 207 BOD (Biological Oxygen Demand), 19 Bones, 124 Bones Processing, 124 Bordas Process, 70 Briquetting Technology, 211 Brooms, 142 Bulk Density, 40 Burning, 49 Direct Burning, 49 Calorific Value, 21 Chemical Toilet, 182 Chinese Biogas, 115 Chrome Tannery, 194 C-N ratio, 21 Coal Pelleting, 55 COD (Chemical Oxygen Demand), 20

Index Combined Tannery, 194 Compost Classification, 66 Compost System, 66 Composting Methods in Villages, 76 Factors Affecting Composting Rate, 67 Ideal Compost, 76 Selection of Composting Method, 77 Uses, 75 Composting, 21, 154 Conservancy System, 157 Contamination, 20 Dairy Cattle Waste, 87 Dano Bio-Stabilizer, 70 Densification, 22 Detention Period, 101 Digestion, 20 Direct combustion, 210 Domestic Waste Storage and Collection, 132 Dry Rendering, 120 Dumping, 146 Dustbin, 134 Earp-Thomas Process, 70 Effluent, 83 Classification, 83 Types, 83 Energy, 27 Farm Animals, 209 Generation, 27 Municipal Solid Waste, 209 Rural Waste Management, 30 Estimates, 6 Household Estimates, 7 Population Estimates, 6 Quantity of Residue, 46 Waste Collection, 13 Waste Generation, 11 Waste Recycling, 14 Ethanol Production, 65 Evapotranspiration, 176 Excreta Disposal, 156 Methods, 157 Fat Settling Tank, 120

216 Fermentation, 21, 155 Fermentation Process, 99 Frazer Process, 70 Fuel Ethanol Production, 65 Methane Recovery, 150 Methanol Production, 63 Garbage, 19 Grinding, 154 Refuse, 40 Gasification, 56 Charcoal, 56 Gasifier Downdraft Gasifier, 59 Engine, 58 Fluidized Bed Gasifier, 59 Suspended Fuel Gasifier, 59 System, 57 Updraft Gasifier, 58 Gasifiers, 57 Gur Industry, 192 Hand Carts, 143 Home Rendering, 124 House Waste Treatment and Disposal, 143 Humus Content, 92 Hydrolysis, 64 Imhoff Tank, 178 Design, 178 Merits and Demerits, 180 Operation, 180 Incineration, 153 Incinerator, 21 Indore Method, 69 Landfill Gas Composition, 151 Landfill Gas Utilization, 152 Latrine Bavla Type, 167 Bore Hole, 159 Deep Trench, 183 Dugwell, 160 NEERI, 167 PRAI, 167 RCA, 164 Sanitary, 159

217 Shallow Trench, 182 Simple Septic, 161 Trench, 159 Water Seal, 162 Leachate, 149 Leather Industry, 193 Leather Board, 194 Semi-Finished Leather Processing, 194 Liquefaction, 61 Direct Liquefaction, 63 Indirect Liquefaction, 61 Litter Bins, 143 Manure Chemical Nature, 39 Composition, 38 Management, 89 Poultry Manure, 96 Pumps, 94 Storage, 94 Manurial Value, 28, 66, 90, 196 Methane Recovery, 150 Methanol Production, 63 Nitrogen Conservation, 74 Open-Kettle Method, 124 Oxidation Pond, 177 Paddy Crop, 47 Utilization, 47 Paddy Husk, 191 Paper Processing, 193 Paru Fuel, 52 Pit Method, 73 Plant Waste, 46 Agro Wastes, 48 Densification, 49 Disposal, 46 Energy Value, 48 Industrial Utilization, 47 Poultry Waste, 88 Processing of Blood, 129 Processing of Clean Fat, 123 Protein Conversion, 96 Protein Extraction, 95 Protein Recycling, 96 Public Education, 155 Putrefaction, 20 PV (Permanganate Value), 21

Index Pyrolysis, 21, 50 Equipment used for Pyrolytic Coal Production, 53 Pyrolytic Coal, 53 Refuse, 42 Ramp Method, 148 Recovery of Technical Fat, 123 Recycling, 19 Reduction, 154 Refuse, 19, 40 Collection, 135 Collection Vehicles, 136 Cost of Collection, 135 Disposal, 152 Disposal Methods, 146 Kitchen Refuse, 144 Records of Collection, 136 Recovery, 143 Routes of Collection, 135 Rendering, 21 Rice Mill Byproducts, 190 Rice Bran, 191 Rice Husk, 190 Rubbish, 19 Rural Waste Compaction Characteristics, 40 Fixed Carbon, 41 Heating Value, 41 Volatile Matter, 41 Salvaging, 155 Sanitary Landfill, 146 Factors, 149 Methods, 148 Requirement, 147 Sanitation, 20 Seepage, 176 Septic Tank, 171 Cleaning, 175 Dimensions, 174 Disposal, 175 Settleable Solids, 20 Sewage, 20 Shovel, 142 Slaughterhouse Waste, 119 Sludge Disposal, 183 Soak Pit, 176 Street Cleansing Waste, 141

Index Street Washings, 19 Subsurface Disposal, 175 Surface Water Pollution, 150 Suspended Solids, 22 Swine Waste, 89 Synthesis Gas, 62 Technologies for Composting Beccari Process, 70 Bordas Process, 70 Dhano process, 70 Earp-Thomas Process, 70 Frazer Process, 70 Indore Method, 69 Moisture Control, 73 Pit Method, 73 Vam Process, 71 Verdier Process, 70 Windrow Systems, 71 Trench Method, 148 UOD (Ultimate Oxygen Demand, 21 Uses of Biogas, 98 Utilization of Animal Fat, 124 Vam Process, 71 Vegetable Tannery, 193 Verdier Process, 70 Waste, 2 Agricultural, 9 Behavioral Waste, 141 Characterization, 37 Chemical Parameter, 34 Collection Systems, 139 Commercial, 7 Compaction Machines, 50 Bullock-operated, 50 Composition, 13, 34, 38

218 Definitions, 2 Domestic, 7 Generation in Rural Areas, 9 Generation in Urban Areas, 7 Generation through Disposal, 9 Handling, 17 Industrial, 8 Institutional, 8 Management, 18 Natural Wastes, 141 Particle Size Distribution, 84 Physical Parameters, 34 Residential, 7 Rural Waste Diseases, 25 Problems, 26 Rural Waste Management, 17 Solid Wastes, 3, 4 Composition, 12 Environmental Hazards, 3 Impacts, 3 Sources, 7 Sources of Different Wastes, 6 Types, 6 Utilization, 18 Waste Cleaner, 53 Waste Collector, 53 Waste Grinder, 54 Waste Pyrolyzer, 54 Waste Water CBRI Disposal System, 185 Water Pressure Digesters, 113 Wet Rendering, 119 Windrow Systems, 71