Cannabis/Hemp for Sustainable Agriculture and Materials 9811687773, 9789811687778

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Dinesh Chandra Agrawal Rajiv Kumar Muralikrishnan Dhanasekaran   Editors

Cannabis/Hemp for Sustainable Agriculture and Materials

Cannabis/Hemp for Sustainable Agriculture and Materials

Dinesh Chandra Agrawal • Rajiv Kumar • Muralikrishnan Dhanasekaran Editors

Cannabis/Hemp for Sustainable Agriculture and Materials

Editors Dinesh Chandra Agrawal Department of Environmental Engineering and Management Chaoyang University of Technology Taichung, Taiwan

Rajiv Kumar QLEAP Academy Pune, Maharashtra, India

Muralikrishnan Dhanasekaran Department of Drug Discovery and Development Harrison School of Pharmacy, Auburn Univ Auburn, AL, USA

ISBN 978-981-16-8777-8 ISBN 978-981-16-8778-5 https://doi.org/10.1007/978-981-16-8778-5

(eBook)

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, 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. 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. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

With profound gratitude, the editors dedicate this book to their beloved parents for their unwavering support and for creating a fulfilling life

Preface

Global warming/climate change and environmental pollution, be it air, water, or soil, can no longer be ignored, and mitigation of these major threats and challenges is no more an option. Sustainable agriculture plays an important role in sustaining the environment. Several intertwined factors influence sustainability in general and sustainable agriculture in particular. Economy and ecology have to cooperate instead of competing with each other. If ecology is pitched against the economy, the former is set to be the looser. Hence, any small step, which promotes cooperation between ecology and economy, is the need of the hour and deserves encouragement by all stakeholders like governments, farmers, entrepreneurs, and society. The cannabis/ hemp research and usage got a significant further boost due to the recent development of December 20, 2018, when the US President signed the farm bill, which de-scheduled hemp, making cannabis under 0.3% tetrahydrocannabinol, the main psychotropic cannabinoid of cannabis, legal once again. This is bound further to hasten up the legalization and commercialization of industrial hemp globally. Cannabis/hemp or industrial hemp, an almost non-psychotropic plant species of cannabis (Cannabis sativa L) as an agricultural crop, provides the hope for long-term sustainable development and growth. There are several advantages of hemp cultivation. It grows fast, thereby consuming 3 to 4 times more CO2, the most abundant greenhouse gas, per hectare per year compared to forest or other common crops. Being one of the first few domesticated plants, hemp has adapted to a broad spectrum of climatic conditions over a period of time. Hemp, a very robust plant, requires relatively little inputs and care. Hardly any other plant/crop can match the advantages of hemp. The whole hemp plant, be it seeds, flowers, leaves, stalk, or even roots, is useful to humans. A large canvas of its applications ranges from healthcare (cannabidiol and seeds), clothing, ropes fashion fabric, to a plethora of common and advanced materials used for construction, (hempcrete) 3-D printing filaments, highend green composites, replacing harmonic steel, conserving heritage building using its anti-insect plaster and painting, phytoremediation, reclaiming wasteland and many more.

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This book on Cannabis/Hemp for Sustainable Agriculture and Materials provides an excellent review from subject experts covering hemp cultivation for sustainable agriculture. Chapter 1 explores the hemp sustainability issues in agronomic and systems contexts and discusses some of the challenges to scale up, emphasizing the need for further research in the agronomical and related aspects of hemp as a viable agriculture crop. Further, this chapter also provides an excellent evaluation of the bottlenecks and guarded optimism of hemp cultivation for commercial purposes. Chapter 2 provides an in-depth understanding of the opportunities and limitations of sustainable hemp cultivation from global and Indian perspectives. Details about the potential of hemp-derived products demonstrate that hemp as a crop can marry ecology with the economy, and both can grow together, a critical requirement for sustainable agriculture. Chapter 3 evaluates the sustainable uses, opportunities, and also limitations of the hemp crop. The details about the agronomy and ecophysiology of hemp cultivation in the different regions of the world are also evaluated and reviewed in Chapter 4. As the potential commercial use of hemp-derived products is rapidly expanding, researchers/innovators are increasingly protecting their inventions through patents. Chapter 5 reviews complete patent literature since the publication of the first hemp patent in 1856 till the end of 2020, providing an excellent insight into the business growth and future potential of hemp for industrial applications along with regionand sector-wise patenting activity to industrial hemp. The potential of hemp seeds for nutritional food is described in Chapter 6. The hemp and hemp waste for livestock feed is covered in Chapter 7. An exciting application of hemp-derived products as green construction materials is reviewed in great detail in Chapter 8. However, Chapter 9 describes hemp-derived carbon for wastewater treatment/ water purification, further extending the scope of hemp-derived products for eco-friendly commercial uses. Chapter 10 provides an overview of cannabis cultivation and legal aspects in Africa. Finally, Chapter 11 provides an interesting review of the potential environmental impact of cannabis cultivation in Africa. In short, this book provides complete details about the hemp agriculture and commercial uses of hemp-derived products. It provides a direction to researchers and entrepreneurs to further explore the immense potential of industrial hemp, which offers hope for sustainable living and growth. The editors hope that this unique compendium of review articles on the cultivation and applications of hemp will be quite useful as a reference book for advanced students, researchers, academics, business houses, and all individuals interested in medicinal, nutritional, traditional, legal, and commercial aspects of hemp/industrial hemp. Taichung, Taiwan Pune, India Auburn, USA 28 October 2021

Dinesh Chandra Agrawal Rajiv Kumar Muralikrishnan Dhanasekaran

Acknowledgments

The editors thank all the invited authors to this book for preparing their valuable manuscripts. Without their contributions, this book would not have been possible. The co-editors Dr. Rajiv Kumar and Professor Dhanasekaran wish to place on record special appreciation and thanks to Professor Agrawal for his untiring efforts in handling the entire correspondence with the Springer Nature team and authors and dealing with the major editing and revision process of manuscripts and managing them from start to finish. Editor Professor Agrawal thank Professor Tao-Ming Cheng, President of the Chaoyang University of Technology (CYUT); Professor Wen-Goang Yang, VicePresident, CYUT; Distinguished Professor Hsi-Hsien Yang, Dean, College of Science and Engineering, CYUT; Professor Wei-Jyun Chien, Chairperson, Department of Applied Chemistry, CYUT, Professor Jih-Hsing Chang, Chairperson, Department of Environmental Engineering and Management, CYUT, Taiwan, for their constant support and encouragement during the progress of the book. Editor Professor Dhanasekaran thanks the administrators, faculty, and staff in Harrison School of Pharmacy, Auburn University, and all his beloved students for their relentless dedication and inspiration. The editors sincerely thank the entire Springer Nature Singapore Pte. Ltd. team concerned with the publication of this book. Editors thank and appreciate their respective families (Manju, Somya, Neha, and Mihir—Family Agrawal; Anu, Sharmishtha, Amit, Swati, and Atanu—Family Rajiv Kumar; Madhu and Rishi—Family Dhanasekaran) for the encouragement and wholehearted support during the progress of the book. Editor Dr. Rajiv Kumar wishes to gratefully acknowledge his grandfather (Late) Mr. Radhakishan Chaturvedi, who got him interested in the fascinating area of Cannabis sharing his vast knowledge and experience about the medicinal aspects of Cannabis leaves (Bhang). The editors express profound gratitude towards “The Infinite Being,” “Lord Shiva, the Adiyogi” for providing guidance, strength, and skill to accomplish the arduous task of handling this book.

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Contents

Industrial Hemp as a Crop for a Sustainable Agriculture . . . . . . . . . . . . Kristine Ely, Swarup Podder, Matthew Reiss, and John Fike

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Industrial Hemp for Sustainable Agriculture: A Critical Evaluation from Global and Indian Perspectives . . . . . . . . . . . . . . . . . . Abhitosh Tripathi and Rajiv Kumar

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Cannabis/Hemp: Sustainable Uses, Opportunities, and Current Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kristine Ely, Swarup Podder, Matthew Reiss, and John Fike

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Agronomy and Ecophysiology of Hemp Cultivation . . . . . . . . . . . . . . . . Henri Blandinières and Stefano Amaducci

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Patenting Journey of Hemp and Development of Various Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Abhishek Choudhury and Rajiv Kumar Industrial Hemp and Hemp Byproducts as Sustainable Feedstuffs in Livestock Diets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 Kristine Ely and John Fike Biotechnological Transformation of Hempseed in the Food Industry . . . 163 Barbara Farinon, Romina Molinari, Lara Costantini, and Nicolò Merendino Current Trends in Applications of Cannabis/Hemp in Construction . . . 203 Tarun Jami, Sukhdeo R. Karade, and Lok Pratap Singh

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Hemp-Based Materials for Applications in Wastewater Treatment by Biosorption-Oriented Processes: A Review . . . . . . . . . . . . . . . . . . . . 239 Chiara Mongioví, Nadia Morin-Crini, Vincent Placet, Corina Bradu, Ana Rita Lado Ribeiro, Aleksandra Ivanovska, Mirjana Kostić, Bernard Martel, Cesare Cosentino, Giangiacomo Torri, Vito Rizzi, Jennifer Gubitosa, Paola Fini, Pinalysa Cosma, Eric Lichtfouse, Dario Lacalamita, Ernesto Mesto, Emanuela Schingaro, Nicoletta De Vietro, and Grégorio Crini The Cannabis/Marijuana (Cannabis sativa L.) Landscape in Africa: An Overview of its Cultivation and Legal Aspects . . . . . . . . . 297 Godwin Anywar, Esezah Kakudidi, Patience Tugume, and Savina Asiimwe Potential Impacts of Cannabis sativa L. Cultivation on the Environment in Africa: A Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 Savina Asiimwe, Patience Tugume, Esezah Kakudidi, and Godwin Anywar

Editors and Contributors

About the Editors Dinesh Chandra Agrawal Ph.D. is a professor in the Department of Environmental Engineering and Management and the Department of Applied Chemistry, Chaoyang University of Technology (CYUT), Taiwan. In 2013, he superannuated as a chief scientist and professor of biological sciences after serving for more than 31 years in the Council of Scientific and Industrial Research (CSIR), Ministry of Science and Technology, Govt. of India. He has about 40 years of research experience in plant biotechnology of diverse species, including medicinal plants and mushrooms and has more than 200 publications, including six books (four by Springer Nature). Professor Agrawal was awarded several prestigious fellowships, including the Alexander von Humboldt Fellowship (Germany), Visiting Scientist to Mississippi State University (USA), British Council Scholar (UK), and European Research Fellow (UK). Since 2016, Professor Agrawal has been serving as associate editor-in-chief of the International Journal of Applied Science and Engineering (Scopus).

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Rajiv Kumar Ph.D. is a co-founder and executive director of QLEAP Academy, India; former chief scientist and head of Tata Chemicals Innovation Centre, Pune, India; and former head of Catalysis Division, National Chemical Laboratory, Pune. He has received several awards like the Eminent Scientist Award of the Catalysis Society of India, Chem-Con Distinguished Scientist, Dr. K.G. Naik Gold Medal for Excellence in Chemical Sciences and Technology, Best Scientist of the Year Award of NCL Research Foundation, and Young Scientist Award (Bhattacharya Medal) of the Catalysis Society of India. His areas of interest and expertise include zeolites, catalysis, biosynthesis of nanomaterials, cannabis/hemp, environment, and sustainability. He has approximately 180 papers published in scientific journals and more than 65 patents to his credit. He is/has been a member of the editorial boards of Applied Catalysis-A, Advances in Nano-porous Materials and Pollution Research. He has guided approximately 20 Ph.D. and M.Tech. students.

Muralikrishnan Dhanasekaran Ph.D. is a professor at Harrison School of Pharmacy, Auburn University, USA. He obtained his Ph.D. from the Indian Institute of Chemical Biology, Kolkata, India, and then received his postdoctoral training from renowned scientists Dr. Manuchair Ebadi (the University of North Dakota) and Dr. Bala Manyam (Scott & White Clinic/Texas A&M, USA). Dr. Dhanasekaran’s research areas are pharmacology, neuroscience, toxicology, dietary, natural products, and the development of drugs/compounds targeting Alzheimer’s and Parkinson’s disease. Dr. Dhanasekaran completed the New Investigator Research Grant from Alzheimer’s Association, several Auburn University grants, and several other research projects from a pharmaceutical company. Dr. Dhanasekaran has guided 16 students (as a mentor) and currently has 5 graduate students under his leadership, and he has trained more than 50 undergraduate students in his lab. Dr. Dhanasekaran has received several teaching awards from Auburn University. He has published more than 200 scientific abstracts, 103 peer-reviewed publications, 2 books, and several book chapters.

Editors and Contributors

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Contributors Stefano Amaducci Università Cattolica del Sacro Cuore di Piacenza, Piacenza, Italy Godwin Anywar Department of Plant Sciences, Microbiology and Biotechnology, Makerere University, Kampala, Uganda Savina Asiimwe Department of Plant Sciences, Microbiology and Biotechnology, Makerere University, Kampala, Uganda Henri Blandinières Università Cattolica del Sacro Cuore di Piacenza, Piacenza, Italy Corina Bradu Department of Systems Ecology and Sustainability, PROTMED Research Centre, University of Bucharest, Bucharest, Romania Abhishek Choudhury Nanobiz India Private Limited, Pune, India Cesare Cosentino Istituto di Chimica e Biochimica G. Ronzoni, Milan, Italy Pinalysa Cosma Dipartimento di Chimica, Università degli Studi “Aldo Moro” di Bari, Bari, Italy Lara Costantini Department of Ecological and Biological Sciences (DEB), Tuscia University, Viterbo, Italy Grégorio Crini Laboratoire Chrono-environnement, UMR 6249, UFR Sciences et Techniques, Université Bourgogne Franche-Comté, Besançon, France Kristine Ely School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, USA Barbara Farinon Department of Ecological and Biological Sciences (DEB), Tuscia University, Viterbo, Italy John Fike School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, USA Paola Fini Consiglio Nazionale delle Ricerche CNR-IPCF, UOS Bari, Bari, Italy Jennifer Gubitosa Dipartimento di Chimica, Università degli Studi “Aldo Moro” di Bari, Bari, Italy Aleksandra Ivanovska Department of Textile Engineering, Innovation Center of the Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia Tarun Jami Council of Scientific and Industrial Research—Central Building Research Institute (CSIR–CBRI), Roorkee, India Academy of Scientific and Innovative Research, Ghaziabad, India RMIT University, Melbourne, Australia GreenJams BuildTech Private Limited, Visakhapatnam, India

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Esezah Kakudidi Department of Plant Sciences, Microbiology and Biotechnology, Makerere University, Kampala, Uganda Sukhdeo R. Karade Council of Scientific and Industrial Research—Central Building Research Institute (CSIR–CBRI), Roorkee, India Academy of Scientific and Innovative Research, Ghaziabad, India Mirjana Kostić Department of Textile Engineering, Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia Rajiv Kumar QLeap Academy, Pune, India Dario Lacalamita Laboratoire Chrono-environnement, UMR 6249, UFR Sciences et Techniques, Université Bourgogne Franche-Comté, Besançon, France Eric Lichtfouse Aix Marseille University, CNRS, IRD, INRA, Coll France, CEREGE, Aix-en-Provence, France Bernard Martel Ingénierie des Systèmes Polymères, Université de Lille, UMET UMR 8207, Villeneuve d’Ascq, France Nicolò Merendino Department of Ecological and Biological Sciences (DEB), Tuscia University, Viterbo, Italy Ernesto Mesto Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari “Aldo Moro”, Bari, Italy Romina Molinari Department of Ecological and Biological Sciences (DEB), Tuscia University, Viterbo, Italy Chiara Mongioví Laboratoire Chrono-environnement, UMR 6249, UFR Sciences et Techniques, Université Bourgogne Franche-Comté, Besançon, France Nadia Morin-Crini Laboratoire Chrono-environnement, UMR 6249, UFR Sciences et Techniques, Université Bourgogne Franche-Comté, Besançon, France Vincent Placet FEMTO-ST, CNRS/UFC/ENSMM/UTBM, Department Applied Mechanics, Université Bourgogne Franche-Comté, Besançon, France

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Swarup Podder School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, USA Matthew Reiss School of Architecture and Design, Virginia Tech, Blacksburg, VA, USA Ana Rita Lado Ribeiro Laboratory of Separation and Reaction Engineering— Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de Engenharia, Universidade do Porto, Porto, Portugal Vito Rizzi Dipartimento di Chimica, Università degli Studi “Aldo Moro” di Bari, Bari, Italy

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Emanuela Schingaro Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari “Aldo Moro”, Bari, Italy Lok Pratap Singh Council of Scientific and Industrial Research—Central Building Research Institute (CSIR–CBRI), Roorkee, India Academy of Scientific and Innovative Research, Ghaziabad, India Giangiacomo Torri Istituto di Chimica e Biochimica G. Ronzoni, Milan, Italy Abhitosh Tripathi Consultant (Independent), Gautam Budhha Nagar (Noida), Uttar Pradesh, India Patience Tugume Department of Plant Sciences, Microbiology and Biotechnology, Makerere University, Kampala, Uganda Nicoletta De Vietro Dipartimento di Chimica, Università degli Studi “Aldo Moro” di Bari, Bari, Italy

Industrial Hemp as a Crop for a Sustainable Agriculture Kristine Ely, Swarup Podder, Matthew Reiss, and John Fike

Abstract Industrial hemp (Cannabis sativa L.) has considerable potential as a sustainable crop for numerous existing industrial and consumer products, with many more likely still to be realized. Much early excitement about this ancient crop arose from its assumed capacity to supply renewable feedstocks (e.g., fibers, grain, biomolecules) for numerous uses, both with little environmental “footprint” and the ability to be recycled or upcycled. Although many tout hemp as the solution for all things, such enthusiasm should be tempered by issues of historical precedent and of scale. First, the lack of research investment during the decades-long restriction in the West ensures that time will be needed to develop sustainable hemp production systems. Even as these systems are developed, there are questions about the capacity to grow sufficient amounts of hemp to meet the needs for an array—and large volume—of products. Still, there is room for guarded optimism that as the crop comes “on line,” it will receive the research needed to make the plant a viable resource for farmers and society. This review explores hemp sustainability issues in agronomic and systems contexts and touches on some of the attendant challenges to scale-up. Keywords Hemp · Sustainability · Production challenges

Abbreviations CBD IPCC LED NRCS

Cannabidiol Intergovernmental Panel on Climate Change Light-emitting diode Natural resources conservation service

K. Ely · S. Podder · J. Fike (*) School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, USA e-mail: jfi[email protected] M. Reiss School of Architecture and Design, Virginia Tech, Blacksburg, VA, USA © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 D. C. Agrawal et al. (eds.), Cannabis/Hemp for Sustainable Agriculture and Materials, https://doi.org/10.1007/978-981-16-8778-5_1

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1 Introduction Industrial hemp (Cannabis sativa L.) is known as a multi-purpose crop, and few other crop species have such broad potential as a source of food, feed, fiber, bioenergy, medicine, phytoremediation, and more. A number of publications provide some sense of hemp’s history and value for human societies (Clarke and Merlin 2013; Small 2015; Fike 2019), and it is not our purpose to chronicle those aspects in detail here. It should suffice (and perhaps provide prologue) in saying that hemp has served as a foundational grain for early human societies (Li 1974); that lessons learned from working with cords from hemp fiber likely helped propel the development of human intellectual and engineering capacity (Adovasio et al. 2007; Karen 2008); and the plant’s biomolecules were important for medicinal, ritual, and religious purposes (Clarke and Merlin 2013). That there has been a great degree of enthusiasm for returning hemp to the fold of agronomic crops should not be surprising, then, when one considers hemp’s history as a plant for body, mind, and spirit. This chapter discusses the production of industrial hemp in a sustainability context. Our goal is to consider how hemp can or should be used to improve farm and cropping system sustainability while touching on some of the knowledge gaps that must be addressed if hemp is to help meet such ends. But first, to frame the issue, we will briefly consider sustainability and sustainable agriculture in a general sense.

2 Sustainability and Sustainable Agriculture Using the simplest definition in the etymological sense of the word, “sustainability” means the ability for some resource or process to be maintained or sustained. Put into an ecological context, this represents a level of use that does not deplete the natural resource base, with rates of resource replacement equal to or greater than rates of resource use. Sustainable processes also would not contaminate or harm the environment in a way that prevents suitable ecosystem function. Current scales of resource use by modern human society are not sustainable—at least not in the manner in which modern societies currently consume resources. Earth systems are challenged by humanity’s resource use, both in terms of depletion and of contamination. While greenhouse gas emissions and global climate change have received greater attention in terms of our current unsustainable trajectory, some also consider biodiversity loss as an important driver of ecosystem change (Hooper et al. 2012). Although some have argued that humanity has the capacity to engineer itself out of such problems (Sabin 2013), it remains to be seen whether this is possible or simply an overly optimistic “cargoism”—that is, the idea that technology will solve all of our resource issues (Catton 1980). While it is not our place to attempt to settle this debate, the reader should recognize that agriculture has been a major contributor to environmental degradation—through deforestation, biodiversity loss,

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soil erosion, waterbody eutrophication, aquifer and surface water depletion, pesticide loading, oceanic dead zones—and that it has the potential to, indeed must be a significant component of the solutions to these issues (Scherr 2016). We ask then, “What is ‘sustainability’ in an agricultural context?” Often sustainability, or more specifically sustainable agriculture, gets defined in terms of the “triple bottom line.” Sustainability may also be described, metaphorically, as a threelegged stool. Such framings come from the recognition that sustainability has economic, social, and environmental contexts or features that must be considered. If a practice cannot sufficiently fulfill functions in all three categories, it is destined for failure. For example, a practice that the broader society favors, and which provides environmental benefits nevertheless will not last long in capitalist economies if it cannot provide a reasonable return on investment. Indeed, this scenario has been identified as a potential challenge for hemp (Young 2005). Likewise, financially rewarding practices that improve environmental outcomes will not be implemented if they are disdained by the broader society. Not long ago, the connection of hemp with marijuana was an important social constraint for adopting the industrial form of the crop. For another example of the social challenge, one need only consider the resistance to siting renewable energy systems such as wind turbines and solar arrays (Pasqualetti 2011). This digression provides a good jumping-off point in the discussion of hemp as a sustainable crop. Indeed, the arguments in favor of legalization (at least in the US) frequently and largely were based on the idea that hemp farming would support greater sustainability. Often this support gave way to unfounded hyperbole about the plant’s many beneficial properties, some of which were “reported” or at least restated in the research literature (description by Summerscales et al. 2010, section 2.2). During the pre-legalization days, the senior author of this chapter was frequently told by hemp enthusiasts that the plant’s powers were such that it could grow on any soil, without added nutrients or other inputs, that it had no insect or disease pests, and that the succeeding crop in the rotation would be the “best ever.” This is no small set of feats, but Cherney and Small (2016) noted the even more optimistic claim that hemp would be “Humankind’s savior.” Hemp certainly has the potential to contribute to cropping systems and societal sustainability, all messianic claims aside, but it remains to be seen how significant this contribution can be. An early life cycle assessment concluded that hemp production systems would require fewer energy inputs and have less climate change impact than existing cash crops such as wheat, corn, potato, and sugar beet (van der Werf 2004). Coupled with these benefits were reduced potential to cause eutrophication and acidification of water bodies (van der Werf 2004). However, and despite this promise, hemp remains an annual crop. Like most annuals, it needs to be seeded each year and requires some level of fertility to be productive. Minimizing soil disturbance and optimizing fertility inputs are critical components of annual cropping system sustainability (Goulding et al. 2008; Hobbs et al. 2008; Pretty 2008), and hemp is no exception. The crop also can be challenging to establish, and work remains to refine no-till establishment practices, which are important for reducing erosion, maintaining soil health, and potentially increasing soil carbon

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sequestration (Langdale et al. 1979; Fu et al. 2006; Baker et al. 2007; Montgomery 2007; Idowu et al. 2009). Research efforts are also needed to develop integrated pest management practices (Britt et al. 2019, 2020; Cranshaw et al. 2019) and incorporate the crop into rotations within diversified cropping systems (e.g., Gorchs et al. 2017; Parenti et al. 2020). Although the degree to which hemp can improve sustainability on the farm remains a question, it is beyond the farm gate, through its use in a variety of consumer and industrial products, that the plant has the greatest potential to help meet broader societal sustainability goals. For example, an early Popular Mechanics (Anonymous 1938) article suggested hemp could be used in more than 25,000 products—though in this chapter, we discuss but a few. Whether realistic or not, this possibility was the primary basis for placing so much hope in hemp prior to its recent legalization. Here too, whether the reality will match the potential remains to be seen, but expectations must be tempered with the fact that hemp received little agricultural, industrial, or consumer products research for most of the twentieth century. It will take time and investment if this crop is to become a significant and valuable contributor to agriculture and the broader society.

3 Farming and Production/Processing Opportunities Numerous and significant opportunities exist to use hemp at scales that could benefit the development of more sustainable, circular economies. But for all the promise and high praise, major questions and challenges to the view of hemp as “humankind’s savior” must be addressed. First among these might be “How can we sustainably grow all this stuff?” Thus, we consider hemp production through a sustainability lens after first briefly discussing some issues of scale. Any assumptions about hemp as a renewable resource (or replacement for non-renewable materials) should be grounded in the reality of what it would take to “get there.” Considering the following, contrasting conditions are required to incorporate hemp into current global markets at a meaningful scale. For our first example, consider that nearly 67 million metric tons of synthetic fibers were produced in 2018, along with about 26 million metric tons of cotton fibers (TextileExchange 2019). Cotton, the leading natural fiber source on the market (Bevilacqua et al. 2014), is associated with significant environmental impact through heavy irrigation and pesticide use for production, with minimal opportunities beyond the use for fabric (Muzyczek 2020). In addition, processing cotton for the fashion industry adds substantially to cotton’s environmental costs. If one assumes an average of 3 metric tons of bast fiber produced per hectare, over 22 million hectares of hemp would be needed to supplant synthetic fibers and nearly nine million hectares to replace cotton production (Duque Schumacher et al. 2020). Compared with current worldwide cotton acres (about 33 million ha) (Meyer 2021), hemp could play a substantial role in reducing requirements for land dedicated to fibers.

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Next, consider the requirements for hemp production as part of an effort to address the expansive carbon footprint of the building industry. To move this to scale would put substantial demand on cropland, even for seemingly small fractions of hemp in the product. E.g., global concrete production alone is estimated at 30 B Mg (Monteiro et al. 2017). Replacing 1% of this mass with hemp hurds would require 300 M Mg of hemp (assuming 50% of the stalk is recoverable hurd). Even with a high production rate of 12.4 Mg ha 1 (6.2 Mg hurds ha 1), over 48 M ha would be needed (whereas US corn and soybean production uses about 38 M ha and 36 M ha, respectively). While the opportunity is great, so too is the challenge to scale to a meaningful capacity.

3.1

Challenges to Sustainability

Earth’s ecosystems face significant sustainability challenges. The need to address humanity’s existing impacts on the planet (IPCC 2021) must be considered in the context of a burgeoning and wealthier human population placing increasing demands on global resources. Global building stocks are likely to double from 2020 to 2060 (Architecure2030.org n.d.). The need for food production is expected to increase more than 50% by 2050 to meet projected population growth (Ranganathan et al. 2018; Searchinger et al. 2019; Babson 2021). Meeting these needs without consequent and substantial land-use change and further ecosystem degradation will be an effort in agricultural intensification—and a significant challenge. Agriculture, which has been a significant contributor to ecosystem disruption (German et al. 2017), will instead need to be part of the solution if humanity is to make progress toward greater sustainability (LaCanne and Lundgren 2018; Gosnell et al. 2019). The potential uses for hemp (Ely et al. 2022) would seem a compelling basis for adopting the crop into sustainable agricultural production systems that supply renewable feedstocks to a circular economy. Still, despite the broad perception of hemp as a crop for greater sustainability, the literature holds little to support (or detract) from this claim. Although the potential applications and corresponding scale at which hemp could be grown are significant, substantial agricultural issues also must be addressed if hemp is to fulfill this role. Thus, we turn to brief discussions of the agronomics and attendant issues confronting the crop in its several forms. Readers interested in a more in-depth discussion of hemp and hemp agronomy should read Williams (2019) and particularly Kostuik and Williams (2019) and Williams and Williams (2019).

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The Special Case of Indoor Cannabinoid Production in a Sustainability Context

Before discussing hemp in field-scale production systems, we take a brief aside to consider hemp in an “indoor agriculture” context. Although touted as an environmentally friendly and highly sustainable crop and a sustainable solution for numerous industries (Karche and Singh 2019), a flower grown for cannabidiol (CBD) production may not easily fit that mold. An estimated 80% of hemp grown for CBD in the US and Canada is grown indoors in either purpose-built or retrofitted structures, with over half (54%) of those operations dedicated to solely indoor production (Cannabis Business Times 2021). Indoor production offers an opportunity for greater production, with lower risk and fewer security concerns, but this comes with a price. Cultivating CBD indoors under controlled conditions allows maximized output with multiple crop cycles but with high manufacturing costs (García-Tejero et al. 2019) and significant energy inputs (i.e., supplemental lighting, temperature and humidity control, watering systems, and natural gas used for supplemental CO2 production) that greatly increase the system’s carbon footprint. However, not all CBD operations are equal offenders, and the energy consumption is better on a sliding scale. Certain geographical locations are better suited for indoor production due to a reduced energy footprint based on the influence of more ideal local climatic conditions (Summers et al. 2021). The development of indoor agriculture is also being facilitated by light-emitting diode (LED) grow lights and solar panel installation. However, indoor production is extremely energy-intensive, and currently, only 5% of energy needs can be generated by rooftop solar panels (Mills and Zeramby 2021).

3.1.2

A Brief Description of Field-Scale Production Systems

As has been implied, hemp production systems generally are considered among three or four types. We briefly characterize these systems here both for clarity and to set the stage for the remaining discussion. With grain production systems, seeds are planted at relatively low rates, and grain is harvested once seeds begin shattering from intermediate inflorescences. Grain cropping often utilizes monoecious varieties (that is, plants that have both male and female flowers on the same stalk), although dioecious grain varieties (with separate male and female flowers) are also available. Fiber crops are planted at high rates with dioecious varieties that are typically quite tall—although there is a site-specificity, as we describe below. For the highest quality fibers, these varieties are harvested near the flowering time. Still, asynchronous flowering can challenge as male plants in some varieties may flower and begin to senesce earlier than the females. In outdoor cannabinoid production systems, spaced plantings, typically at very low density, are common. Only female plants are maintained. Males are eradicated to avoid pollination because seeds reduce extraction efficiency.

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Efforts are also given to “dual-purpose” systems, in which hemp cultivars are grown for at least two product outputs. This typically refers to hemp seed + fiber systems in which inflorescences are harvested (combined) for seed before the residual stalks are collected for fiber. Some efforts too, have been given to collecting grain and chaff in seed + cannabinoids systems, or flowers and stalks for cannabinoids + fiber. Making hemp a “triple threat” crop seems unlikely but is a point of effort among some in the industry. Doing so would certainly seem to meet the definition of agricultural intensification.

3.1.3

Cultivars

“What variety should I grow?” is often one of the first questions that producers ask about new crops. For hemp, this is a multi-layered question, given that multiple forms of the crop (i.e., fiber, grain, cannabinoid, and multipurpose varieties) have striking differences in management inputs and morphology. Moreover, substantial genotype  environmental interaction in morphological expression can occur. Although some cultivars are photoperiod insensitive and begin flowering once they reach adequate growth (Cherney and Small 2016), most grain and probably all fiber hemp is photoperiod sensitive. Growing varieties of northern origin at more southern latitudes exposes them to short days sooner than would occur near their latitude of origin. This signals the plant to enter reproductive development, and this earlier flowering shortens the crop height significantly (Fig. 1). Conversely, growing a variety of southern origins at greater (more northern) latitudes can increase plant height. Exceedingly short grain or fiber plants can result in significant yield drag, whereas overly tall plants, particularly for grain, could be a challenge to harvest. Systems built on “dual-purpose” production in which both

Fig. 1 Northern adapted industrial hemp (Cannabis sativa) fiber variety (foreground) established late in the season. Photo credit: John Fike

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grain and the residual stalk are harvested must balance these issues (along with any differential valuation for the amount and quality of components harvested). Cannabinoid production systems—frequently based on transplanting seedlings or clones into a field—were not immune to the size challenge either, as very tall plants could be quite productive and labor-intensive for harvest and processing. In contrast, short varieties could be easy to handle but produce a limited yield. Adaptation of a cultivar to a site is also relevant to pest and disease resistance, and we will discuss this briefly below. For now, suffice to say that hemp cultivars’ development will be site and cropping system-specific. This makes for a bit of a moving target for breeders, given that the industry is at such an early and uncertain stage of development.

3.1.4

Establishment: Seeds, Soils, and Seeding Depth

Although Cannabis has often carried the epithet of “weed,” this moniker seems not to apply to fields under modern “broad acre” cultivation techniques that rely on tillage systems or herbicides for ground preparation and vegetation management and on drills for seed placement. On the contrary, the poor establishment is one of the primary reasons for failure in hemp production systems (Kostuik and Williams 2019). Poor seed placement can have significant adverse effects on stand establishment, and while common recommendations are to plant at 0.5–1.0-cm depth, success or failure can occur at greater or lower planting depths depending on several factors, including seed quality, soil type, and conditions, and timing and intensity of precipitation around the time of planting. Seed quality (e.g., germination percentage and vigor), important for successful field establishment and crop production, can be a significant issue for the nascent industry, particularly imported seeds. Low germination rates can be offset with higher planting rates to a degree, but this does not necessarily overcome poor vigor. Even seeds with a high germination rate can have low emergence due to poor vigor. Despite claims that hemp will grow anywhere, it is sensitive to its growing environment. Heavy clay soils are challenging for the small, low-vigor seeds. Even if the plant establishes and grows, it may be unproductive, and the plant also does not like waterlogged conditions (Fig. 2). Adjusting seeding depth so that seeds are placed near the zone of available moisture can be a useful approach for establishment. Admittedly, this observation is based on experience in the field, as there is little to confirm this in the literature. Planting deeper in sandy soils—with less moisture-holding capacity and less likelihood of crusting—may be a useful strategy. Shallower planting is warranted in soils with greater clay content unless surface conditions are dry and no precipitation is expected for several days. Moisture, essential for stand establishment, can be a killer if it arrives as heavy precipitation following seeding—particularly if seeds are planted into loose soil.

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Fig. 2 In the top image, clear differences in stand establishment are visible and correspond with clear differences in soil texture. The lighter color area (with poorer stands) corresponds with heavier clay and lower soil organic matter. In the lower image, growth across the field started uniformly, but above-average seasonal precipitation caused moisture accumulation in low areas toward the back of the field that resulted in hemp mortality. Photo credit: John Fike

3.1.5

Field Preparation: Tillage/No-Tillage and Cover Crops

Most hemp establishment guides involve some level of tillage for field preparation, with recommendations that soils be cultivated and firm at planting. This has practical implications for sustainability. Development of large-scale hemp industries that require thousands of acres that must be tilled for successful establishment—would work against current efforts to encourage no-till production methods (NRCS 2016). Although time and corresponding management such as cover cropping may be needed to see the benefits of no-till production (Didoné et al. 2017; Cusser et al. 2020; Daryanto et al. 2020), the practice is generally recognized for reducing erosion and compaction (Mchunu et al. 2011; Komissarov and Klik 2020; Carretta et al. 2021), for increasing soil moisture, carbon, and biological activity (Jemison et al.

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2019; Somasundaram et al. 2020), and for reducing labor, fuel consumption, and emissions (Gozubuyuk et al. 2020; Stošić et al. 2021). As such, no-till management (particularly when combined with cover cropping) offers an opportunity for improved environmental and economic outcomes as part of a path to sustainable intensification (Nunes et al. 2018; Cusser et al. 2020). Hemp field establishment is difficult in both tillage regimes, but long-term, we consider that no-till will be a viable production method in broadacre hemp production scenarios. Current challenges must be addressed, however, if no-till will routinely be viable and effective. Refining planting methods, cover crop systems, and cover (residue) management will be central to this effort in the short term. Hemp may become a cover crop in its own right, in time, although early research suggests it will be less efficacious than other species (Rühlemann and Schmidtke 2016). Over time, varietal development that addresses seedling vigor will facilitate a more robust and successful establishment.

3.1.6

Planting Date and Soil Conditions

Generally, hemp’s seeding time is similar to corn, occurring when soil temperatures reach around 15  C. However, hemp can also tolerate colder environments and germination temperatures (Haney and Kutscheid 1975; Byrd 2019). Earlier seeding is recommended for greater vegetative growth over the season—especially for fiber production—but this must be weighed against varietal adaptation to cooler climates and growing conditions. Too, low soil temperature and elevated soil moisture associated with spring weather conditions may make field preparation and establishment challenging.

3.1.7

Seeding Rates and Row Spacing

The seeding rate varies with the end use of the given production systems. Greater seeding rates are needed to achieve the plant populations desired for fiber production and typically are in the 45–70 kg ha 1 range. The greater plant density discourages branching and early flowering and supports greater fiber quality. Conversely, low seeding rates (10–45 kg ha 1) for lower plant densities are required in grain production systems; this stimulates greater branching, which leads to higher grain yield. The wide range in seeding rates for each type reflects differences in seed weight as well as vigor and emergence by variety. In time, plant populations are likely to be a more common descriptor for planting recommendations, at least for fiber. Amaducci et al. (2002) suggested fiber crops were best grown at about 180–270 plants m 2, but Townshend and Boleyn (2008) reported that agronomic management and climatic factors had a bigger impact on grain yield in their research. Spacing also varies with the production system. Row to row distances are narrow (often 7–20 cm) for fiber plantings, while wider spacings (15–30 cm) are used for grain production. Much wider spacing has been used for producing crops for cannabinoids (and other molecules of interest).

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Typically, “flower” hemp seedlings or clones are transplanted into bedded fields following a production model similar to that for tobacco or horticultural crops. Wide (often 1+ m) intra- and inter-row spacings are used to support branching development with high rates of flower production. These highly intensive production systems are “built” on significant inputs used to develop the planting material, irrigation, frequent cultivation or use of plastic “mulch” (derived from petroleum) for weed control, and much labor. Such systems would not be considered sustainable given their resource demand. However, the high costs of this production method are leading growers to explore ways to generate hemp in broad acre production. Also, the acres needed to meet market demand are limited.

3.1.8

Fertility Needs for Hemp Production

For any crop production system, nutrient management is a central component both to productivity and sustainability given the effects on land use, greenhouse gas emissions, water quality, and economic outcomes (Johnson et al. 2007; Snyder et al. 2009; Smith et al. 2014; Plastina 2019; Santoni et al. 2019). The tradeoffs in energy inputs vs. system outputs (Heitschmidt et al. 1996) must be balanced given human need and very real implications for land use under low input scenarios—thus the push for sustainable intensification (Snyder et al. 2009). The embedded energy inputs used to make synthetic fertilizers are substantial (Brentrup et al. 2016), and their misuse causes a host of environmental problems. Thus, a more efficient (if not entirely sustainable) fertility management will be based on the use of the best fertilizer inputs (Wang et al. 2017) and application to meet crop needs in order to reduce losses to the environment (Johnson et al. 2007). Such approaches to managing fertility inputs will be an essential part of developing sustainable hemp production systems. However, hemp production must be considered in systems (vs. merely “crop production”) contexts, as energy and fertility inputs and outflows may vary substantially based on management across the value chain (e.g., Oenema et al. 2001). We will touch on this issue briefly below and in the discussion of hemp processing and retting. In the specific case of hemp production, nutrient input requirements may vary substantially based on the different hemp production systems, cultivars, geographic location, and soil conditions, among others (Adesina et al. 2020). As with other cropping systems, previous cropping history and soil nutrient status need to be considered before fertilizers are applied to hemp in order to minimize the potential for over-application. This may sound straightforward, but to date, only a few studies (at least they are few relative to other commodities) have been conducted to address nutrient requirements for hemp in various soil types and production systems. Some confusion may arise over seemingly contradictory results in the literature regarding hemp’s response to N. This likely stems from significant fertility x environment (i.e., location) interactions that have been observed within and among experiments (Aubin et al. 2015; Tang et al. 2017b; Papastylianou et al. 2018). Results can further be affected (or confounded) by differential cultivar response to N (Papastylianou et al. 2018) or differences in planting density or desired end

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product (Campiglia et al. 2017). Fertility input levels may affect stand density, as self-thinning has been observed at N application rates greater than 80 kg N ha 1 (van der Werf et al. 1995; van der Werf 2004). Fertility input management also affects product quality, adding another wrinkle in the management needs and constraints with the crop. These results speak to the need for tailored recommendations (by site, cultivar, and management for target end products) to optimize outputs in response to inputs. Typical N recommendations for fiber production are in the 50 to 100 kg ha 1 range, with positive responses to as much as 240 kg N ha 1 reported (Papastylianou et al. 2018). Generally, grain systems require more N than fiber production, and recommendations often range from 100 to 150 kg ha 1. A positive, linear response to N at rates up to 200 kg ha 1 was observed by Aubin et al. (2015), who did not find a maximum rate for grain. The authors suggested that higher N rates may be needed in more humid environments, citing the work of Vera et al. (2010), who reported maximum yields at about 150 kg ha 1 in a drier environment. However, whether a response to greater fertility in humid environments reflects greater use or greater loss from the environment remains to be explored. Soil organic matter also supports greater productivity and crop quality and may lower N response (Wilsie et al. 1942). Fewer studies of response to P or K are available. Similar to other crops, plant responses to P depend on initial soil levels, with little or no response observed in high-fertility environments. Early research recommended P at 30 kg P ha 1 for optimum fiber production (Jordan et al. 1946). Phosphorus inputs are more important for grain than fiber hemp because seeds store substantial amounts of organic P required for seedling growth (Lott et al. 2000). There seems to be some corroboration of this idea from Vera et al. (2010), given that grain types were more responsive to P than dual-type cultivars. Similar to P, studies on the response to K requirements are limited, with that research suggesting little if any response to K (Aubin et al. 2015). Uptake may be greater in and for stalk development (see Kostuik and Williams 2019). This would suggest a greater need for fiber production systems if the plants are not retted in the field (see below). Nutrient deficiencies or imbalances seem more common in indoor and outdoor cannabinoid production settings. This may reflect challenges of managing nutrients through fertigation, limitations with artificial growing media, or both. Interestingly, our in-field observations of hemp with deficiency symptoms in the southeast US suggest that boron deficiency is perhaps the most common among micronutrients, and some initial work has been conducted by Veazie et al. (2020). For hemp (or any crop), sustainability in a nutrient-input context must address ways to manage supplies, limit environmental impacts, and optimize the energy outputs per unit input. For P, finite supplies and the environmental damage caused by losses from agricultural systems present the most prominent sustainability challenges (Tomlinson 2010; Rhodes 2013). Were hemp to be used at the scale required for the numerous construction and fabrication activities proposed, its carbon sequestration, nutrient “pull,” and land use demands would all be substantial? (Recall our acreage numbers for hempcrete at the start of this section.)

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At about 78% of the earth’s atmosphere (as N2), Nitrogen presents no resource concern in terms of supply. Still, losses from the system can cause significant adverse impacts to water quality and environmental quality more generally. Both the fossil energy inputs used to synthesize N fertilizers, and their transformation to N2O in the field represent significant challenges to sustainability from a greenhouse gas emissions perspective. Even though hemp may have greater N use efficiency than other fiber crops (at least at low N input levels (Tang et al. 2017a), substantial amounts of N and other nutrient inputs would be needed to support high production levels and minimize conversion from other land uses. The new methods of N fertilization are being developed, which might reduce the reliance on synthetics, but while a budding body of literature addresses this possibility with traditional row crops, only limited work with hemp has been published to date (Zarei et al. 2014; Da Cunha Leme Filho et al. 2020; Kakabouki et al. 2021). It is also possible that hemp waste products could be used as feedstock for synthetic N production (Bertilsson and Kirchmann 2021). However, these systems will need more development, refinement, and scale-up and may still present environmental concerns.

3.1.9

Pests—Weeds, Insects, Diseases, and Birds

Despite the promotional wishful thinking that hemp suffers no weeds, insects, or disease pressure, these problems can be challenging. Few registered herbicides exist that are efficacious against weeds but not against hemp. Sandler and Gibson (2019) went so far as to publish a call for weed research in industrial hemp after finding only three articles that specifically addressed weed management. Since that call, one herbicide evaluation has been published in the reviewed literature (Flessner et al. 2020). More commonly, applied agronomic methods—planting timing, row spacing, seeding rate, and brute force (i.e., mechanical or hand weeding) have been the fallback strategies most typically deployed by farmers and researchers. Weeds may be challenged to compete with hemp in fiber production systems, given the high plant populations. Spacing and timing may be more critical with grain systems, but results of agronomic management have proven variable in the limited available research (Sandler and Gibson 2019). In the CBD production systems, mulching or cultivation is often the management tool of choice. This is likely because flower production systems often adopt a more organic production posture—or at least, producers shy away from pesticides due to concerns about a residual contaminant in the extracted products. Still, the high level of energy inputs (as plastic or routine cultivation) for flower production indicates these systems could do much more to achieve greater production system sustainability. To some degree, our understanding of hemp and insect challenges is a relearning of knowledge lost or abandoned when the crop itself was stigmatized. Simple database searches will turn up publications on hemp and insects dating back at least to the early twentieth century in a variety of locations (e.g., a small selection includes Anutchin 1916; Vinal 1917; Takahashi 1919; Dudley 1920; Pliginski 1922;

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Popov and Startzeva-Klementz 1928; Harada 1930; Martelli 1938). These reports perhaps speak both to the vast geographic production and the challenge that insect pressures represented for the crop historically. As hemp is “reopened” to investigation, a number of insect pests have been identified (again) in North America and globally (Cranshaw et al. 2018; Britt et al. 2019; Kucuktopcu et al. 2020; Schreiner and Cranshaw 2020). However, insect damage often may not pass an economic threshold (Kostuik and Williams 2019), and some data suggest hemp can have a high level of productivity even in the face of significant defoliation (Britt et al. 2019). Efforts to control hemp pests with traditional insecticides and integrated pest management strategies are a work in progress (Cranshaw et al. 2019; Kucuktopcu et al. 2020). As with weeds, insecticide options that pass regulatory muster currently are limited; thus, a renewed look at old literature may prove helpful for developing new strategies to deal with hemp’s pests. For example, past research suggests hemp could serve as a trap crop (Shchegolev 1937), and breeding for insect resistance also should be possible (Lihvari and Arinstein 1944; Haeng Ree 1966; Grigoryev 1998; McPartland 2002). Insect management for sustainable hemp production systems varies markedly depending on the type of end product and the synchrony of development between plant host and insect pest. Although several insect species consume hemp, in the US, greater attention has been given to the production and quality losses caused in flower crops—and much of this damage occurs at the jaws of corn earworm (Helicoverpa zea) and other Lepidoptera (Britt et al. 2020). However, developmental timing and migratory patterns of earworms in the US are such that varietal selection may offer an opportunity to avoid pest issues. Choosing varieties that flower well before the pest’s arrival or after its departure may help producers sidestep severe attacks. (Of course, varietal selection based on floral development would not be a solution for avoiding less mobile mites (Acari) and aphids (Hemiptera)). Such selection considerations may also be useful to avoid these pests in hemp grain production systems. Earworms may be of little worry for fiber hemp producers, for whom stem borers (e.g., Ostrinia nubilalis and Grapholita delineana) may present the greater challenge. Intriguingly, borer damage to main stems may benefit production in grain crops by stimulating branching (Small et al. 2007). Ačko et al. (2019) also reported similar and cultivar-specific responses to apical bud defoliation. As hemp production expands, more challenges relative to pests are likely to arise, and seemingly unrelated management decisions may affect pest pressures. Insect pests can respond to nutrient inputs, adding another interaction to manage in these emerging production systems (Bolt et al. 2021). Similarly, insect behavior changes were observed in response to graminicide application, though the degree to which such practices are management issues remains to be seen (Durak et al. 2021). Of course, insects also may present sustainability problems beyond the direct effects of plant depredation, as they can be important vectors for disease (e.g., Hadad et al. 2019; Giladi et al. 2020). Once harvested, hemp grain may be subject to damage by several species, including a number of beetles (Coleoptera) and the Mediterranean flour moth

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Fig. 3 Bee (Hymenoptera) pollinating industrial hemp (Cannabis sativa) plants. Photo credit: John Fike

(Ephestia kuehniella) (Cominelli et al. 2020; Hamilton et al. 2021). Indian meal moth (Plodia interpnuctella) has also been observed in hemp seed (Fike, personal observation), and likely more species will become apparent as hemp grain production and storage increase. This can be a significant issue without appropriate management, as losses in storage can be as great as losses during the growing season (Peairs 2010). Despite these challenges, there are positive attributes of hemp-insect interactions. Hemp has the potential to support pollinators and other insect populations that face significant decline. As a prolific pollen producer, hemp may serve as an excellent food resource, particularly for bees (Hymenoptera) (Fig. 3). The potential benefit likely will be greatest with fiber hemp grown in more varied landscapes, as bees make greater use of hemp when plants are taller and in locales with greater diversity (O’Brien and Arathi 2019; Flicker et al. 2020). Hemp also may serve as a source of novel chemistries for insect management. Various molecules or extracts from hemp have been associated with reduced herbivory and can have insecticidal and larvicidal properties (Benelli et al. 2018; Dhakal et al. 2019; Zagozen et al. 2019; Ahmed et al. 2020; Mantzoukas et al. 2020; Tabari et al. 2020). Hemp essential oil can be an effective larvicide to pest species (i.e., flies (Diptera), aphids, mosquitoes, etc.) while non-toxic to desired species (i.e., ladybugs (Coccinellidae) and earthworms (Annelida)), thus opening the opportunity for a sustainable and eco-friendly insecticide (Benelli et al. 2018; Rossi et al. 2020). Such findings present new arenas for exploration and possible opportunities for sustainable agricultural management. Several “first reports” of hemp diseases and pathogens have been made as hemp has returned to production or received increased observation (including, among others, Schappe et al. 2020; Amaradasa et al. 2020; Szarka et al. 2020; Garfinkel 2020;

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Fig. 4 Birds leaving industrial hemp (Cannabis sativa) grain crops. Photo credit: John Fike

Ren et al. 2021). More than 100 diseases have been identified in the crop (Şevik 2020). Likely many were seen/known, but unnamed historically, given our progress in techniques for determining species. As with other pests, disease pressures would be expected to increase as crop acres expand. Producers and industry in the US have indicated that addressing disease and pathogen issues will be valuable to the growing industry, although currently, it is not the highest of priorities (Ellison 2021). Efforts to address the array of diseases or their vectors may be approached with traditional inputs (Pluzhnikova et al. 2020) or even hemp extracts (Nissen et al. 2010; Benelli et al. 2018), but long term will be better approached through targeted breeding and appropriate management practices that reduce disease presence, susceptibility, or both (Weldon et al. 2020; Stack et al. 2021). We would not normally consider birds as pests in the context of modern agricultural production systems—clearly, we have moved beyond the era of the scarecrow. However, in choosing to include birds in a section on pests, we note that we are not the first authors to do so (McPartland 1996; McPartland et al. 2004; Čeh and Čremožnik 2016; Cizej and Poličnik 2018). How much loss do birds cause in agricultural production systems is an open question—and perhaps another potential use of hemp is supporting avian and other wildlife. E.g., hemp seed has served as a significant food source for mourning doves (Zenaidura macroura; McClure 1943) and quail (Coturnix; Robel 1969), a species of concern given population decline. We have observed birds walking the rows to pick up seeds dropped by the planter—in which case the damage could be near complete—but problems in small plot research more typically occur at harvesttime. However, depredation of small plots by wildlife probably presents an outsized problem relative to the damage seen at the field scale. Moreover, given significant declines in bird populations over the last 50 years, perhaps some compromise is possible, such that growing hemp can be valued for its grains and for its ability to support specific bird populations (Fig. 4).

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Harvest and Processing Issues Shattering and Uneven Maturity in Grain Crops

Shattering represents another route of loss from grain production. Female and monoecious hemp plants have terminal inflorescences, and seeds in the inflorescences are bound by bracts (small, specialized leaves). Ripening seeds generally mature from the bottom of the inflorescence (which flowers earlier) to the top. The uneven ripening within and among hemp plants means that some seeds will remain unfilled or in a dough stage when grain fill is complete for others, and these ripe seeds often shatter earlier. In the long term, hemp breeding programs should be able to make progress in reducing shattering and making ripening more uniform (Soroka and Tarakan 1981). For now, most grain farmers harvest before all seeds are mature to reduce shattering losses and prevent wrapping stalks on combine harvesters (Kostuik and Williams 2019). However, this adds the requirement that seed be dried mechanically and within a short window of time to avoid spoilage and the development of bacterial contaminants. The grain also will need to be cleaned; this additional handling increases the risk of hulls cracking and consequent seed quality loss (Kostuik and Williams 2019). Of course, all these steps and inputs add to the carbon footprint for hemp as grain.

3.2.2

Optimal Harvest for Fibers

As noted previously (Ely et al. 2022), hemp fibers have potential use in numerous manufacturing applications, but they are likely to have the greatest value if used in textiles. In this regard, hemp may be a compliment to, if not a replacement for cotton, but only if the plant can be harvested and processed in a way to achieve textilequality fibers. For the best fiber quality, hemp must be harvested at or before the female plants flower. Typically, 20% of females in flowers is the biological gauge for determining harvest timing. Once a hemp plant enters the flowering stage, it must reinforce its stalk to accommodate the weight of a developing seed head. Lignification of bast fibers reduces fiber quality and increases the difficulty of processing. Moreover, the stalk adds secondary hurd fibers, another antiquality component from a processing standpoint (Westerhuis et al. 2019), at least in the context of textiles. Dual-purpose (grain + fiber) crops may well find markets for the hemp fibers, but they will not be used for high-value textiles. The yield and quality of fiber crops can vary dramatically by cultivar and both planting and harvest dates, and understanding these factors will be essential for optimizing harvest.

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Harvest and Preprocessing Across Hemp Platforms

As with other commodities, grain harvesting relies on combine harvesters. Grain systems may have larger carbon footprints since the hemp grain routinely is harvested at high moisture to reduce seed shatter. The moist seed and associated chaff must be moved from the field and dried directly after harvest. Typically, this adds to the crop’s carbon footprint as natural gas or other fossil fuels are needed as a heat source, and additional energy is needed to clean the seed. Flower crop harvest methods range from hand cutting to mechanical harvest. Following harvest, stems or whole plants may be hung and air dried or placed in controlled environments that use heat and forced air for rapid drying. In some cases, whole plants are harvested with combines or forage harvesters. The resulting chopped material can be dried, or it may be baled and wrapped (making a silage that is suited for hydrocarbon-based extraction systems). Generally, flower production and the related downstream extraction systems are energy-intensive, but they will not have the scale of fiber production. Hemp fiber harvest historically has utilized hay cutting (or similar) equipment that severed and laid the plants on the ground. More modern hay harvesting equipment cuts the stalks and then crimps and scatters the stems to some degree. Indeed, some fiber processors have recommended tedding the crop to get more uniform drying and retting. However, specialized machinery may be needed if plants are excessively tall, thus too big for traditional hay or downstream processing equipment, or if they need to be kept in alignment to facilitate downstream processing steps. In this regard, greater processing flexibility (i.e., ability to take varied orientation of plant material) will increase flexibility for harvest systems and post-cut management. Several companies have developed modifications for traditional combine harvesters in order to capture multiple resources from hemp plants. Some modified harvesters can collect leaves and flowers for cannabinoid extraction while simultaneously cutting the stalks for retting and subsequent fiber processing (https://www. global-equipment.com/hemp-harvesting-equipment). Similar systems have been developed for grain + fiber harvest. Those focused solely on cannabinoids have modified combines to capture the flower fraction and remove the majority of the stalk material (https://www.usahempcombine.com/). These modifications or the development of new “hemp-specific” equipment will make economic sense to the degree that they can reduce labor costs and allow for successful, cost-effective processing. For fiber systems, once plants are cut, they traditionally were left in the field to ret. Retting (i.e., allowing stems to rot to the point that bast and hurd fibers are easily separated) has been successful in varied environments, and historically has been a critical step in achieving high-quality fibers (Réquilé et al. 2021). Although a detailed discussion of retting and downstream processing is beyond this chapter’s scope, suffice it to say that the need (or not) for retting has important implications for sustainability. Retting allows many of the nutrients in the hemp plant to return to the

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soil as leaves shatter and decay; this reduces the demands for external inputs to maintain soil fertility. However, field retting increases the risk surrounding the collection of high-quality fiber due to variable weather conditions. Newer process systems that utilize the whole plant without in-field retting will change the calculus for retting in terms of nutrient removals (Gusovius et al. 2019). Those systems, too, may further challenge sustainability metrics if they require greater energy inputs or generate large amounts of wastewater (Sadrmanesh and Chen 2019) during processing. As markets develop and mature, we might anticipate a more nuanced approach to fiber production. If demand for hurd increases more than the demand for high-quality fibers, there may be an optimum point where lower bast quality is more than offset by increased hurd yield. This might change the approach to harvest timing, and growers could delay harvest to increase hurd yields. Also, a better understanding of fiber kinetics as a function of harvest timing and processing may give new means of utilizing fibers for higher-end uses (e.g. (Guessasma and Beaugrand 2019).

3.2.4

Inadequate Processing Capacity

For any crop or production system, all links in the supply chain must be sound for the system to function properly, and we digress here with a brief, cautionary tale. After hemp production became legal in the US, much excitement was generated by the potential to grow high-value cannabinoid crops. High prices for bulk flower in the spring of 2019 had many people thinking they could gross $86,000 to $124,000/ hectare, and such dreams of rapid wealth (or saving the farm) spurred many—both farmer and non-farmer alike—to grow the crop. However, a difficult reality hit in the fall of the same year when many growers could not find processors for their plant material, and values for bulk hemp dropped to as low as $25,000/hectare. (Hempgrower.com 2019, citing spot biomass prices from PanXchange. See Midpoint Biomass Spot Price. Estimated returns are based on an assumed 1120 kg flower/ha yield, 10% CBD in bulk flower, and $6.6 to $11 USD per CBD percentage point per kg biomass.) In turn, processors folded because they couldn’t make sufficient income once flower prices collapsed (hempindustrydaily.com 2020). Although the market appears to be working its way to maturity, those prices have never come back and are unlikely to do so, particularly as systems undergo greater mechanization. Certainly, processing capacity remains a problem for hemp as an industrial-scale fiber or grain crop, but the matter is rooted in deeper risk issues. Fledgling enterprises routinely face the “chicken or the egg” question—i.e., “which comes first, the growers or the processors?” (Fike et al. 2007), and the question is who will risk the capital to start the enterprise. That is, farmers will feel little commitment to grow solely on the promise of an as-yet-established processor planning to pay an uncertain and unguaranteed price. In turn, a processor wanting to make a substantial investment in a facility will require some promise of engaged farmers who can and will grow the crop. This problem echoes throughout the supply chain. For example, it

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may be challenging for a processor to develop, scale, and sell its new, hemp-based materiel to a manufacturer with significant demand and access to competing materials that have already passed existing regulatory standards.

3.3

Hemp as a Complement to (or Replacement for) Existing Commodities

Although hemp has potential as a major commodity crop in the not-too-distant future, creating such a reality will take substantial effort all across the supply chain. At the farm level, such a reality will require hemp’s integration into existing production systems at a scale that will be sufficient for industry needs. This will require evaluating the crop in terms of which varieties and production windows both meet satisfactory yield and quality goals within any given ecoregion. It will also mean developing management practices (to include no-till, cover cropping, and crop rotations) amenable to sustainable production. Layered over top of this will be the need to meet specific processor needs, standards, and schedules, which may, in turn, interact with the production system (e.g., in terms of harvest timing and questions of “to ret or not to ret”). For all of these conditions, cultivars with desirable agronomic and processing traits need to be identified and developed to support the needs for industry development. Developing hemp production systems may be fraught with complexity, but a farmer’s decision to grow hemp likely will turn on the rewards for doing so. Producers may be inclined to grow alternative crops, but only if they provide substantial benefits relative to other commodities. There will be no move to an alternative crop if it does not increase revenue, reduce costs, or convey other value or benefit relative to the current cropping system.

4 Conclusion Hemp has an extensive history of cultivation across the globe, and humans have found a variety of uses for the plant’s fibers, seed, and biomolecules. The recent re-visioning (and legalization) of the plant as an industrial crop was based in part on the idea that hemp can be a renewable resource with the capacity to improve economic, environmental, and social conditions for agricultural communities—and humanity more generally. Growing environmental concerns regarding unsustainable resource use and the contamination of Earth’s ecosystems (to include atmospheric carbon enrichment) are bases for considering hemp as a renewable resource within the framework of sustainable agricultural and manufacturing systems. Hemp has the potential capability to meet economic, social, and environmental conditions relevant to sustainable agriculture principles. That is, hemp production

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can help create and maintain a healthy environment, support farm profitability, and foster social and economic equity. The corresponding scale at which hemp could be grown or would have to be grown to make a substantial contribution to broader sustainability is significant. However, many challenges must be addressed in-field and across various supply chains before hemp can be successfully integrated into (and dare we say central to?) systems of sustainable agriculture and commerce.

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Scherr S (2016) Transforming agriculture from threat to solution for environmental challenges. Ecosystem Marketplace. https://www.ecosystemmarketplace.com/articles/transforming-agricul ture-threat-solution-environmental-challenges/ Schreiner M, Cranshaw W (2020) A survey of the arthropod fauna associated with hemp (Cannabis sativa L.) grown in Eastern Colorado. J Kansas Entomol Soc 93:113–131. https://doi.org/10. 2317/0022-8567-93.2.113 Searchinger T, Waite R, Hanson C, Ranganathan J (2019) Creating a sustainable food future: a menu of solutions to feed nearly 10 billion people by 2050 Şevik MA (2020) An overview of hemp diseases. J Inst Sci Technol 10:748–762. https://doi.org/10. 21597/jist.670642 Shchegolev VN (1937) Effectiveness as a Control Measure of special Sowings of Hemp to attract the Hemp Flea (Psylliodes attenuata Koch. Summary of the Scientific Research Work of the Institute of Plant Protection for the year 1936. Part II Pests and Diseases of industrial and Fruit Crops Small E (2015) Evolution and classification of Cannabis sativa (Marijuana, Hemp) in relation to human utilization. Bot Rev 81:189–294. https://doi.org/10.1007/s12229-015-9157-3 Small E, Marcus D, Butler G, McElroy AR (2007) Apparent increase in biomass and seed productivity in hemp (Cannabis sativa) resulting from branch proliferation caused by the European corn borer (Ostrinia nubilalis). J Ind Hemp 12:15–26. https://doi.org/10.1300/ J237v12n01_03 Smith P, Bustamante M, Ahammad H et al (2014) Agriculture, forestry and other land use (AFOLU). In: Edenhofer O, Pichs-Madruga R, Sokona Y et al (eds) Climate change 2014: mitigation of climate change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge/New York, pp 811–922 Snyder CS, Bruulsema TW, Jensen TL, Fixen PE (2009) Review of greenhouse gas emissions from crop production systems and fertilizer management effects. Agric Ecosyst Environ 133:247– 266. https://doi.org/10.1016/j.agee.2009.04.021 Somasundaram J, Sinha NK, Dalal RC et al (2020) No-till farming and conservation agriculture in South Asia–issues, challenges, prospects and benefits. CRC Crit Rev Plant Sci 39:236–279. https://doi.org/10.1080/07352689.2020.1782069 Soroka VP, Tarakan NI (1981) Anatomical structure of the bracts in hemp varieties differing in degree of fruit shattering. No Dep 3928–81:13 Stack GM, Toth JA, Carlson CH et al (2021) Season-long characterization of high-cannabinoid hemp (Cannabis sativa L.) reveals variation in cannabinoid accumulation, flowering time, and disease resistance. GCB Bioenergy 13:546–561. https://doi.org/10.1111/gcbb.12793 Stošić M, Ivezić V, Tadić V (2021) Tillage systems as a function of greenhouse gas (GHG) emission and fuel consumption mitigation. Environ Sci Pollut Res 28:16492–16503. https:// doi.org/10.1007/s11356-020-12211-y Summers HM, Sproul E, Quinn JC (2021) The greenhouse gas emissions of indoor cannabis production in the United States. Nat Sustain 4:644–650. https://doi.org/10.1038/s41893-02100691-w Summerscales J, Dissanayake NPJ, Virk AS, Hall W (2010) A review of bast fibres and their composites. Part 1 - fibres as reinforcements. Compos Part A Appl Sci Manuf 41:1329–1335. https://doi.org/10.1016/j.compositesa.2010.06.001 Szarka D, Amsden B, Beale J et al (2020) First report of hemp leaf spot caused by a bipolaris species on hemp (Cannabis sativa) in Kentucky. Plant Heal Prog 21. https://doi.org/10.1094/PHP-0120-0004-BR Tabari MA, Khodashenas A, Jafari M et al (2020) Acaricidal properties of hemp (Cannabis sativa L.) essential oil against Dermanyssus gallinae and Hyalomma dromedarii. Ind Crops Prod 147: 112238. https://doi.org/10.1016/j.indcrop.2020.112238 Takahashi S (1919) Notes on insects injurious to hemp and on Thyestes gebleri. Konchu Sekai Gifu 23:20–24

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Tang K, Struik PC, Amaducci S et al (2017a) Hemp (Cannabis sativa L.) leaf photosynthesis in relation to nitrogen content and temperature: implications for hemp as a bio-economically sustainable crop. GCB Bioenergy 9:1573–1587. https://doi.org/10.1111/gcbb.12451 Tang K, Struik PC, Yin X et al (2017b) A comprehensive study of planting density and nitrogen fertilization effect on dual-purpose hemp (Cannabis sativa L.) cultivation. Ind Crop Prod 107: 427–438. https://doi.org/10.1016/j.indcrop.2017.06.033 TextileExchange (2019) Preferred fiber & materials: market report 2019 Tomlinson I (2010) A rock and a hard place: Peak phosphorus and the threat to our food security. Soil Association, Bristol Townshend JM, Boleyn JM (2008) Plant density effect on oil seed yield and quality of industrial Hemp cv. Fasamo in Canterbury. NZGA Res Pract Ser 14:85–91. https://doi.org/10.33584/rps. 14.2008.3180 van der Werf HMG (2004) Life cycle analysis of field production of fibre hemp, the effect of production practices on environmental impacts. Euphytica 140:13–23. https://doi.org/10.1007/ s10681-004-4750-2 van der Werf HMG, van Geel WCA, van Gils LJC, Haverkort AJ (1995) Nitrogen fertilization and row width affect self-thinning and productivity of fibre hemp (Cannabis sativa L.). F Crop Res 42:27–37. https://doi.org/10.1016/0378-4290(95)00017-K Veazie P, Cockson P, Logan D, Whipker B (2020) With cannabis nutrients, hit the boron ‘Sweet Spot.’ Cannabis Business Times. https://www.cannabisbusinesstimes.com/article/cultivationmatters-ncsu-boron-fertilization-nutrition-deficiency-toxicity/ Vera CL, Malhi SS, Phelps SM et al (2010) N, P, and S fertilization effects on industrial hemp in Saskatchewan. Can J Plant Sci 90:179–184. https://doi.org/10.4141/CJPS09101 Vinal SC (1917) The European corn borer, Pyrausta nubilalis Hubner: a recently established pest in Massachusetts Wang ZB, Chen J, Mao SC et al (2017) Comparison of greenhouse gas emissions of chemical fertilizer types in China’s crop production. J Clean Prod 141:1267–1274. https://doi.org/10. 1016/j.jclepro.2016.09.120 Weldon WA, Ullrich MR, Smart LB et al (2020) Cross-infectivity of powdery mildew isolates originating from hemp (Cannabis sativa) and Japanese hop (Humulus japonicus) in New York. Plant Heal Prog 21:47–53. https://doi.org/10.1094/PHP-09-19-0067-RS Westerhuis W, van Delden SH, van Dam JEG et al (2019) Plant weight determines secondary fibre development in fibre hemp (Cannabis sativa L.). Ind Crops Prod 139:111493. https://doi.org/10. 1016/J.INDCROP.2019.111493 Williams D (2019) Industrial hemp as a modern commodity crop. American Society of Agronomy, Madison, WI Williams RA, Williams DW (2019) Cannabinoids-human physiology and agronomic principles for production. Industrial Hemp as a Modern Commodity Crop. pp. 73–91 Wilsie CP, Norman AG, Dyas ES (1942) Hemp: a war crop for Iowa. Agricultural Experiement Station, Agricultural Extension Service, Iowa State College Young E (2005) Revival of Industrial Hemp: a systematic analysis of the current global industry to determine limitations and identify future potentials within the concept of sustainability. Lund University Zagozen M, Kreft S, Cerenak A (2019) Terpenes in hemp (Cannabis sativa L.). Hmelj Bilt 26:157– 168 Zarei M, Tadayon MR, Tadayyon A (2014) Effect of biofertilizer, under salinity condition on the yield and oil content of three ecotype of hemp (Cannabis sativa L.). J Crop Improv 16:517–529

Industrial Hemp for Sustainable Agriculture: A Critical Evaluation from Global and Indian Perspectives Abhitosh Tripathi and Rajiv Kumar

Abstract Although the agriculture and the environment have been sustained for many millennia, these are now under stress and pose a global threat in general and to India in particular, mainly due to wanton exploitation of natural resources for development. The need for sustainable development of agriculture and the environment has never been more urgent than now. Fortunately, industrial hemp, a non-psychoactive species of Cannabis sativa L, offers solutions to address several aspects required for the sustainable development of agriculture and ecology. Because of Cannabis’s fast growth (ca. 4–5 months crop cycle) and capturing 2–3 times the carbon dioxide per hectare per year compared to the forest, coupled with its vast spectrum of applications, hemp presents an excellent opportunity for sustainable agriculture and climate change mitigation. Hemp applications include nutrition (seeds), health care (CBD), fibers (bast and hurd) which can be used for a variety of products like elegant clothes, bags, sanitary articles, high-end paper and construction materials. Also, there are several other new and innovative applications of hemp, such as 3-D printing filaments, nano carbon sheets (supercapacitors, energy storage), jewelry, cables replacing harmonic steel, footwear, etc. Since all these products are made from renewable and fast-growing hemp, they can significantly contribute to sustainable growth, provided suitable and encouraging policies for hemp cultivation and its supply chain are implemented. Hemp can help farmers and entrepreneurs economically and the consumers in getting eco-friendly products from renewable hemp. It has been shown that hemp can help in the sustainable growth of both ecology and economy as both have to grow hand in hand instead of at the cost of each other. India being at the cusp of the next giant leap of development and growth, hemp cultivation must be seriously looked into by the governments, farmers, and enterprises to achieve sustainable agriculture and environment and inclusive and responsible economic growth. In fact,

A. Tripathi Consultant (Independent), Gautam Buddha Nagar (Noida), Uttar Pradesh, India R. Kumar (*) QLeap Academy, Pune, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 D. C. Agrawal et al. (eds.), Cannabis/Hemp for Sustainable Agriculture and Materials, https://doi.org/10.1007/978-981-16-8778-5_2

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hemp can contribute to the United Nation’s 15 out of 17 Sustainable Development Goals (SDGs). Keywords Hemp · Industrial hemp · Cannabis · Sustainable agriculture · Climate change · Environment

Abbreviations BCE Bn CAGR CBD CE ES GDP HBP IFOAM IPCC MDG MFA MT NRC PCT PLA SDG THC UK UN UNDESA UNRMDG USD USDA

Before common era Billion Compounded annualized growth rate Cannabidiol Common era Ecosystem services Gross domestic product Hemp bio plastic International Federation of Organic Agriculture Movement International Panel for Climate Change Millennium development goals Multifunctional agriculture Metric ton National Research Council Patent Co-operation Treaty Poly lactic acid Sustainability development goals Tetrahydrocannabinol United Kingdom United Nations United Nations Department of Environment and Social Affairs United Nations Report of Millennium Development Goals United States Dollar United States Department of Agriculture

1 Introduction It is known that humans have consumed wild grains since more than 100 thousand years ago (Harmon 2009). However, with its cycle of sowing and harvesting to sow again in the next season from the grains/seeds saved from the previous crop, agriculture seems to have started 11,000–12,000 BCE (Small 2017). Human civilization shifted from being nomadic hunter-gatherers to a stable agriculture-based community about 12,000 years ago, and hemp, being one of the first few, if not the

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first, domesticated crop, was cultivated as a source of food and fiber subsequently of medicinal and intoxicating substances. Industrial hemp or simply hemp, a non-psychoactive species of cannabis, commonly referred to as Cannabis Sativa L, is one of the oldest crops domesticated, by humans at least 12,000 BCE (Abel 1980). Every part of hemp plant, be it stalk, flowers and seeds are quite useful for various applications like fibers from stalk, cannabidiol (CBD) from flowers and seeds for foods, proteins and essential oils. CBD is non-psychoactive cannabinoid and has various medicinal uses. Perhaps hemp stands tallest among all other plants as far as a diversity of applications it offers. Hemp is a very robust crop with respect to the agronomical plasticity that is adaptability towards soil and environmental conditions. However, due to its extremely close resemblance with its psychotropic cousin marijuana, hemp cultivation was also banned or restricted in 1960s along with banning and criminalization of marijuana. But due to renewed interest in its new, green and sustainable products, the restrictions on hemp cultivation have started easing out for its industrial applications globally. Cannabis/hemp has been used for a variety of applications like cloths, ropes, paper, sails, food (seeds), medicines, and construction materials in plasters and paints for millennia (Abel 1980; Small 2017). Although hemp was cultivated in almost every part of the world, its psychotropic and medicinal properties were discovered by ancient Indians and Chinese. The flowering tops (ganja), resin (charas or hashish), and leaves (Bhang in India) of cannabis are psychoactive; hence these have been used for medicinal and also for recreational and cultural purposes for ages (Russo 2005; Tikka and D’Souza 2019; Chaturvedi and Agrawal 2021). Because of the psychoactive effects of cannabis /marijuana, which could be misused by and harmful to the users, it was banned and criminalized globally around the 1960s. The legal status of the cultivation of hemp varies from country to country. Some countries allow growing hemp provided it contains a trace amount (ca. 0.3% or less) of tetrahydrocannabinol (THC), the main psychoactive cannabinoid. However, industrial hemp hardly shows any psychotropicity. In India, states like Uttarakhand and Uttar Pradesh have allowed growing hemp, albeit under regulated conditions, for industrial, medicinal, and research purposes in 2018 (The Tribune 2018). In 2019, Madhya Pradesh Government in India announced to legalize the cultivation of cannabis/hemp for medical and industrial purposes (Anonymous 2019). However, one must get the license to grow hemp/cannabis (bhang) in these three states. The hemp plant has several advantages, like fast growth, less or no pesticides, and needs very little attention due to its adaptability to different climatic and soil conditions. Hence, hemp has been a favored agricultural crop for thousands of years (Abel 1980; Small 2017). Although agriculture and the environment have been sustained for thousands of years, recently, in the last 100 years, both agriculture and the environment have faced severe challenges and threats (IPCC 2021). It could be attributed to several reasons like wanton exploitation of natural resources for rapid industrialization and commercial farming instead of sustenance farming, to cater to the food and other needs of increasing population. The green revolution occurred in India and the world

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mainly due to scientific advancements in fertilizers, high-yielding seed varieties, biocides (insecticides, herbicides, and weedicides), and water management. Also, mechanization led to significantly improved agricultural productivity per hectare. Because of this, India became self-sufficient, and an exporter of agricultural produces. However, this development has resulted in environmental and ecological degradation like soil degradation, groundwater pollution, and toxicity due to carrying forward the residual biocides in the agricultural produces consumed by humans and animals. Hence, there are increasing concerns raised by society and governments alike, and a global call for sustainable agriculture and climate change mitigation is becoming louder with each passing day as it has started threatening the sustainable existence of present and future generations (IPCC 2021). The present chapter deals with the potential of industrial hemp (Cannabis sativa L.) towards sustainable agriculture and ecology. The issues and challenges faced by agriculture and the environment will also be briefly discussed, along with the concepts and goals of sustainable agriculture. Whenever ecology is pitched against the economy, the former is ignored as the economy is for today and ecology is for tomorrow. Hence, ecology and economy must go hand in hand for sustainable growth. Whether hemp cultivation can help achieve these goals will be critically evaluated concerning India in this chapter.

2 Sustainability and Sustainable Agriculture 2.1

Climate Change

In a recently published Sixth Assessment Report of International Panel for Climate Change, it has been emphasized that the effects of climate change are “widespread, rapid, and intensifying,” where human actions determine the present and future climate (IPCC 2021). Further, carbon dioxide (CO2) remains the major cause of climate change, in addition to the other greenhouse gases and air pollutants (IPCC 2021). The world population is currently 7.8 Bn (Billion) and is growing at 1.1%, and is expected to drop further to less than 0.1% by 2100 (Roser 2019). However, the population in India is ca. 1.395 Bn and growing at around 0.96% and will plateau by mid-century before it starts decreasing (WPR 2021). The world population is expected to plateau at 10.9 Bn by the turn of the twenty-first Century (UNDESA 2019). This presents certain challenges given the finite nature of terrestrial resources and the ever-imminent global warming. Clearly, there is increasing stress and strain on business sustainability as usual. There is a need to change the way we are going, as climate change, sustainability, and agriculture are intricately interdependent.

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Sustainability

Sustainability is quite a complex phenomenon and depends on several interconnected factors. The complete example of a sustainable system is of nature, where waste generation does not exist. In nature, nothing is produced which cannot be reused and recycled. A very complex interdependent eco-system works quite well in a self-regulated manner. However, in the pursuit of ever-increasing wealth creation for better living, speedy growth in the human population, specifically in the last 100 years, has led humans to exploit nature and natural resources without considering long-term impacts on the climate. The use of renewables and the affordability of eco-friendly products are, among others, important aspects of sustainability. However, affordability may vary from region to region, society to society, and from time to time, as whatever is unaffordable today may become affordable tomorrow. Further, we need to reuse and recycle the byproducts of our activities, be it industrial, social, or agricultural. In fact, agriculture is renewable and takes care of carbon dioxide recycle to a large extent. Since hemp grows fast and consumes large quantities of CO2, a greenhouse gas, compared to other terrestrial plants, its potential as a crop in helping a sustainable environment cannot be ignored. There are five main pillars/factors for sustainable development (Fig. 1), namely: (i) Inclusive human development, (ii) Equitable social development,

Responsible human development

Equitable social development

Sustainable Development

Comprehensive ecological development

Innovative green technology development

Inclusive economic development

Fig. 1 Sustainable development, its factors, and their interdependence

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(iii) Comprehensive ecological development, (iv) Responsible economic development, (v) Innovative green technology development These are rather crucial aspects needed to be attained in the next couple of generations (NRC 1999). Each of these pillars is so intertwined and interdependent that none can sustain at the cost of any other in the long run. These factors constitute a multitude of parameters. For example, human development includes nutritious food, fiber, health, education, shelter, longevity, and basic amenities (Hegde and Sudhakara-Babu 2016). Likewise, equitable and responsible social development constitutes poverty reduction/alleviation, people’s participation and ownership, social justice, and population control/reduction planning (TSDR 2000). Similarly, ecology and ecosystem include main parameters, namely biotic, i.e., plant kingdom (producers), animal kingdom, including humans (consumers), and microbial organisms including fungi (decomposers) (Anonymous 2021). In the same way, the main components of a responsible economy include people participation, opportunity equitability (i.e., more opportunities for more people), overall growth, and sustained and resilient business, social, and governmental planning/decisions (Pacetti 2016). Innovative green technologies, like renewable energy technologies, green batteries and electric vehicles, green chemical and materials technologies, biorefinery technology, new eco-friendly agricultural practices, technologies, etc., are important for sustainable development. Figure 1 exhibits these factors/pillars of sustainability and sustainable development. An unsustainable ecological system adversely impacts future productivity, profitability, economic and human development. Sustainable agriculture plays a crucial role in influencing these factors. Hence, sustainable development strategies need to evolve for sustainable agriculture considering the factors impacted by agriculture, like productivity, economic viability and growth, social responsibility (say, for example, responsible population and demography planning), social equity, and ecological safety and sustenance. While all these aims, goals, or aspirations are quite laudable, the implementation is rather challenging and “easier said than done.” Hence even a small step towards it is a step in the right direction. In this context, we shall evaluate the potential of hemp cultivation to take some definitive steps towards achieving the big goals of sustainable development through sustainable agriculture.

2.3

Sustainable Agriculture and Ecosystem

Agriculture and ecosystem are interrelated to a large extent as both are intricately interdependent and sustain each other. Agricultural practices heavily rely on external inputs, like excessive fertilizers, biocides, water, monoculture farming, mechanization, productivity to improve agricultural income. However, this has led to the decline in the long-term sustenance due to soil erosion, depletion of soil organic

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matter and biological activity, salinization from excessive use of fertilizers and water, and environmental pollution, including groundwater (nitrate and biocides leaching) (Hegde and Sudhakara-Babu 2016). Further, the intensification of commercial farming has disturbed a delicate balance between agriculture and the ecosystem, adversely affecting human and cattle health and threatens long-term sustainability. Although the term “Sustainable Agriculture” is supposed to have been coined by Gordon McClymont (Anonymous 2020), the original reference to this term could be traced to a lecture titled “Towards a Sustainable Agriculture - The Living Soil” delivered by Eve Balfour at International Federation of Organic Agriculture Movements (IFOAM) conference in 1977 (Balfour 1977) advocating an alternate agriculture model having harmony with nature. Similar views were propounded by others (Rodale 1983; Harwood 1990; Douglas 1984; Rao 2002; Sudhakara-Babu 2016) regarding regenerative agriculture where natural soil processes, ecological processes, and economy need to be taken care of to ensure perpetual productivity. Hegde and Sudhakara-Babu (2016) have discussed different aspects of sustainability and sustainable agriculture in detail and summed it up as: “Sustainable agriculture seeks permanence to agricultural production systems to enable food security for all in an ecologically sound, economically viable, and socially responsible manner.” Although an exhaustive discussion on the ambit of sustainability and sustainable agriculture is beyond the primary scope of the present chapter, a reasonable and workable understanding of what constitutes sustainability and sustainable agriculture is rather important. The term ‘sustainable agriculture’ can further and more granularly be regarded as a well-integrated system of plant and animal production with a site-specific application that will, over the long-term, achieve the requirements (USDA 1997; Pretty 2008) as, (i) Satisfy human food and fiber needs. (ii) Enhance environmental quality and the natural resource base upon which the agriculture economy depends. (iii) Make the most efficient use of nonrenewable resources and on-farm resources, and integrate, where appropriate, natural biological cycles and controls (iv) Sustain the economic viability of farm operations; and (v) Enhance the quality of life for farmers and society as a whole. It is also seen that there are different views on the subject from a techno-centric perspective (Multi-Functional Agriculture, MFA) (UNCED 1992; Renting and Rossing 2009) or eco-centric (Ecosystem Services, ES) perspective (Costanza et al. 1997; Nyanga et al. 2020). Though, both the approaches are similar, their perspective of the function of agriculture is different. Over the last 50 years, the growing world population with an ever-increasing demand for greater food and fiber production created a highly mechanized, input, & productivity-driven agricultural from the 1970s. However, over the years, it had detrimental effects on the environment and rural habitat.

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2.4

Factors Affecting Sustainable Agriculture

Sustainable agricultural practices are intended to protect the environment, expand the Earth’s natural resource base, and maintain and improve soil fertility for better economic returns. Based on a multi-pronged goal, sustainable agriculture seeks to (i) increase farm productivity, farm income with environmental stewardship and (ii) increase production for human food and fiber needs, and also contribute towards green and renewable materials and energy requirements for sustainable growth. The specific factors that may influence the sustainability of agriculture are: • • • • • • • •

healthy soil and seeds appropriate water management and irrigation methods (drip, precision) crop planning and crop rotation for improved soil regeneration and crop yield increasing use of modern technology and innovations for informed and precision farming, i.e., agriculture 4.0 tools (Surykumar 2019; Akhilesh and Sooda (2020) organic and eco safer fertilizers and pesticides for crop protection; high quality and nutritious crop production; responsible population policy and human needs (mainly food and fiber); higher economic returns to farmers with the protection of ecology and environment; and suitable agri-eco-system friendly government policies (Hegde and Sudhakara-Babu 2016; Panda and Mondal 2020; Rani 2018).

Figure 2 summarizes these factors and their intercorrelation (Hegde and Sudhakara-Babu 2016; Panda and Mondal 2020; Rani 2018).

Seeds and Soil Health

Ecology / Environment

Water / Irrigation

Crop Planning

Economy / Affordability

Sustainable Agriculture Govt Policies

Modern Technology

Population/ Demography

Fertilizers Pesticides Crop Yield and Health

Fig. 2 Factors influencing the sustainability of agriculture and their interconnectivity

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3 Agriculture in India 3.1

Brief History and Present Status

Agriculture finds elaborate mention in India’s most ancient scriptures, namely Rig Veda and Atharv Veda (Srinivas 2018; Roy 2009). Dedicated text on various aspects of plant and agriculture is compiled in Vriksh Ayurveda (Vriksh means Plant, Ayu means life, Veda means knowledge) written by Salihotra ca. 400 BCE (Srikanth et al. 2015) and codified by Surpala (Sadhale (Tr) 1996), where details about plants, soil types, various stages of agriculture, organic fertilizers, etc. are provided, and has been sustained for several thousands of years (Agrawal 1996). Thus, based on the various evidences, including archeological findings, it can be mentioned that the permanent human settlements, agricultural and animal husbandry practices were prevalent in ancient India/South Asia at least around 9000 BCE (Gupta 2004; Shinde et al. 2019) and predates Indus Valley Civilization era. India ranks first in the world concerning total land under agriculture (arable land), followed by the USA and China. However, it ranks second in total agriculture produce after the USA (Sunder 2018). Because of the green revolution in the 1970s, India became self-sufficient in food production and is now the sixth largest food exporter worldwide, with more than 40 Bn USD in the year 2021 (Ghosal 2021). Although the agriculture sector contributes around 15–17% to India’s GDP, it employs 45–50% of the total workforce (World Bank 2021), indicating the economic stress and relatively meager per capita income in the Agri sector.

3.2

Issues Faced by Agriculture, Specifically from the Indian Perspective

It is worth mentioning that, unlike Europe and North Americas, in India, most of the rivers are forest-fed and not glacier-fed. The forest cover, including the banks of rivers, has been significantly reduced and depleted very rapidly over the past few decades. Therefore, the water holding capacity of the land is also reduced significantly and contributing to land degradation. The soil health and fertility are directly proportional to soil microbial and nutrient concentration, apart from soil moisture. Soil health, crop health, and public health are directly related, as healthy soil leads to healthy crops, leading to a healthy public. The rapid depletion in organic (and microbial) and micronutrients concentration and bio-availability in soil are mainly caused due to indiscriminate and excessive use of inorganic fertilizers, pesticides, insecticides, and water (due to flood irrigation). In addition, the deficiency of micronutrients like minerals, mainly caused by the reduction in organic and microbial concentration leading to the decreasing bioavailability of micronutrients to the crop, results in the decrease in the nutritional value of

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the food produced. With this rate, the agricultural land quality (soil health) and productivity sustained over several thousand years may become unsustainable in the near future (Hegde and Sudhakara-Babu 2016). In order to achieve optimum soil performance, holistic soil management over a number of crop cycles is needed, where soil degradation has to be taken care of. The soil degradation manifests due to the soil quality impairment required for optimum crop growth and productivity. As mentioned above briefly, the quality and, therefore, its performance mainly depends upon the following factors (Hegde and Sudhakara-Babu 2016): (i) depletion of nutrients and organic matter (microbial contents), (ii) impairment of or reduction in soil structure, rooting depth, and tilth, (iii) topsoil erosion caused due to heavy water flow causing reduced water holding capacity as a consequence of erosion, (iv) reduction in soil ecological functions like nutrient cycling and waste decomposition, and (v) nutrient imbalance resulting in salinity, acidity, alkalinity, and accumulation of toxic metals However, the laudable goal of avoiding soil degradation may be ideal, but achieving it is not fully practical. Some soil erosion in crop cycles is inevitable, especially when intensive agriculture is employed against traditional agriculture. To prevent soil degradation and to implement timely remedial measures, focused soil management is required to avoid any deficiency as of and when it occurs. Like soil quality, the importance of seed quality for good crop yield cannot be overemphasized. Poor quality of seeds leads to decreased productivity/yield. Hence, seed enhancement is generally needed before sowing. Such seed enhancement processes include hydration treatments, coatings, seed conditioning, pre-germination, seed priming (including nano-priming), non-invasive magnetic treatment, etc., for increasing vigor and stress tolerance of the crop in the field. The details about these seed-enhance techniques may be found in a recent report by Panda and Mondal (2020). The use of technology in agriculture in developed and certain developing nations is significantly higher than in India. The large-scale mechanization is a challenge since, relatively very small average holding of farmland with Indian farmers. Additionally, India’s population and the world are rapidly increasing and need food with high nutritional value.

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4 Hemp Cultivation Towards Achieving Sustainable Agriculture 4.1

Hemp Cultivation: A Brief History

Cannabis/hemp has played a vital role in the development of agriculture over few millennia in human history and impacted the ecology. Humans have been exploring and manipulating cannabis plants of desired quality for various purposes like fiber, cloths, ropes, medicines, and recreational and cultural applications for many thousands of years. The cannabis plant gradually dispersed through various natural, animal and human intervened ways all across the globe (Clarke and Merlin 2013). Hemp was the third-largest crop grown in many countries, including India and the USA, until the early twentieth century. However, hemp fell from favor in the last century because of the intoxicating properties of cannabis/marijuana, having a remarkably similar appearance with insignificant intoxicating properties of hemp, which has made those in political or religious authority view it negatively. If such was the case, it is important to know why hemp and its sustainability have been under a reexamination for almost the last 7–8 decades, when it is evident that it was agronomical, economical, legal, and environmentally sustainable at one time to grow cannabis or hemp. During the twentieth century, due to many reasons but mainly due to the negative image created around this crop by the rise of other industries and associated lobbies with sustained publicity and propaganda against its psychotropic properties, cannabis was banned (Small 2017). However, this banning, along with criminalization of the cannabis cultivation, use, possession, and trafficking, was not based on a scientific basis but was driven mainly based on certain kinds of morality and motivation (Riboulet-Zemouli et al. 2019). Based on extensive and pressing scientific research and development in cannabis/hemp, mainly from 1970 onwards, it has started to convince the policymakers to relook the legal status of cannabis/hemp considering its medicinal and industrial uses. Hence, significant acceptance in society and policymakers has resulted in the liberalization of cannabis policy in different parts of the world. Several States in the USA have legalized cannabis hemp/ marijuana for medical and recreational uses. In Europe, it is increasingly legalized. In India, Uttarakhand, Uttar Pradesh, and Madhya Pradesh state Governments have recently legalized the cultivation of help for medical, research, and industrial purposes (The Tribune 2018: Anonymous 2019). Perhaps no single plant can boast the large range of utility and possible uses as the industrial hemp/cannabis can.

4.2

Hemp Cultivation and Plant Characteristics

In a classic book entitled “Cannabis: A Complete Guide” by Small (2017), all the aspects of cannabis/hemp (including wild variety) and the details about hemp

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cultivation are excellently delineated and recommended for those interested in cannabis/hemp. However, in this section, we shall briefly cover the various aspects of the hemp cultivation/agronomical aspects, hemp characteristics, and various uses/ applications to determine the suitability of hemp for sustainable agriculture and help farmers increase their income.

4.2.1

Soil and Root System

Industrial hemp commonly possesses an extensive taproot system capable of penetrating deep into the soil to extract water and nutrients required for its relatively fast growth. The main advantages of this type of large taproots include: (i) the recovery of the water and nutrients from deep where these are otherwise unavailable (ii) opens up the soil so that it is better prepared for future crops (Small 2017). However, the hemp root system is very versatile and adaptive to its soil ecosystem. For example, if the soil is coarse, deep with the relatively low water table, and well-drained, the large taproot system (more than 2 M deep) develops. If the soil is medium coarse-textured and water-retaining, the roots can develop ca. 1 M deep with profuse lateral branching. The lateral branching is concentrated first near the surface and towards the end of the primary root so that the plant can get the water at the surface and a moderately deep location. Whereas, in wet and very moist soil, where the water table is near the surface (unsuitable for good growth and yield), hemp roots are quite shallow with lateral branching near the top part of the root system, which can be confused as fibrous instead of tap type root system (Small 2017). Hence it is clear that hemp can grow even in relatively harsh soil and climatic conditions. However, high yielding varieties aimed at specific produces like fiber, grain/seeds, or flowers for CBD as commercial agricultural commodity crops require suitable soil that is coarse, loose, well-drained loam rich in organic matter with pH around 6–7. Similarly, suitable growing conditions (temperature/light, etc.) and inputs like seeds, irrigation, fertilizers, and biocides are required for high-yielding commercial hemp farming. The agronomical aspects of hemp cultivation are covered in great detail by Small (2017); and others (Piotrowski and Carus 2011; Williams 2018; Adesina et al. 2020).

4.2.2

Stem and Foliage

Like the hemp root system, the stem or stalk and foliage also exhibit adaptability and plasticity, specifically in the features of its main stalk and branching patterns and arrangements of its foliage and flowers. The wild and domesticated varieties show different characteristics as the domesticated varieties designed for fiber are taller and less woody, showing less resistance to the wind than their wild cousins. The wild

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varieties are low in stature, with woodier and flexible stems to withstand the wind. However, the hemp and marijuana plants aimed for oilseeds closely resemble wild variety hemp plant characteristics. Plasticity or adaptability, i.e., the timely ability of species to respond and adapt to environmental changes and thereby overcome the challenges thus posed, is the key to survival. Like weeds, hemp (also considered a weed) and the wild plant varieties show higher adaptability than the domesticated ones. This “phenotypic” plasticity, mentioned above, is a consequence of “genotype” plasticity, which allows surviving in a wide range of environmental and soil conditions, specifically under marginal land and climatic conditions (Small 2017). Thanks to many ecological adaptations, Cannabis sativa possesses exceptionally adaptive phenotypic plasticity in the roots and stems. Further, it grows large under favorable conditions and produces many seeds, while under adverse conditions, growth gets retarded and produces fewer seeds to survive. Similarly, a severely damaged stalk can regrow abundantly from the lower branches and tolerates shade despite being a “full-sun” plant (Small 2017). Therefore, this adaptability and phenotypic plasticity make cannabis/hemp a very robust plant that can grow under a wide range of climatic and soil conditions. Abel (1980) in “Marihuana: First Twelve Thousand Years” corroborates and sums the same robustness of hemp/cannabis/marijuana by saying, “Marihuana is one of nature’s hardiest specimens. It needs little care to thrive. One need not talk to it, sing to it, or play soothing tranquil Brahms lullabies to coax it to grow. It is as vigorous as a weed. It is ubiquitous. It flourishes under nearly every possible climatic condition.”

4.2.3

Carbon Capture Capacity

Recently, Toochi (2018) has described the method of calculating the carbon capture by plants. Commonly, the average carbon content is around 50% of the dry weight of the plant (De Wald et al. 2005). Hence, determining the weight of carbon captured by a plant can easily be calculated by multiplying its dry weight by 0.5 (50%). The wt Ratio of carbon dioxide/carbon is ca. 44/12, where the molecular wt. of CO2 is ca. 44, and C is 12. Therefore, the carbon content in a plant (on a dry weight basis) needs to be multiplied by factor 3.67 (44 divided 12). Since the carbon content is ca. 50% of dry plant wt, the weight of CO2 capture by a plant can also be obtained simply by multiplying the plant’s dry wt. by 1.835. The CO2 captured by a plant can reach 1.835 MT per MT dry wt of the plant growth in a year. Hence a simple formula can be written: Wt of CO2 captured ¼ Dry wt of plant/tree  1.835/Years. Hemp is one of the fastest-growing terrestrial plants, clearly indicating the higher carbon capacity per hectare (Ha) per year than other plants and trees. Vosper (2018) demonstrated that one Ha of UK hemp cultivation captures around 10–12 MT CO2 per year, considering one crop per year compared to a dense forest’s carbon capture capacity where one Ha of forest absorbs ca. 4–5 MT CO2 per year (Toochi 2018). Hence, hemp possesses twice the capacity of forest/trees to fix atmospheric carbon, considering one crop cycle a year. Since certain hemp varieties can be harvested

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twice a year, where crop matures in 4–5 months, CO2 capture could be as high as 20 MT per Ha per year, a considerably higher (ca. 4–5 times) than forest/any other agricultural farm. These estimates do not include the roots, which constitute ca. 20% of the mass of the harvested material and remain fixed in the soil. This remaining carbon content in the soil maybe 0.46 to 0.67 MT of carbon per Ha. Vosper (2018) argues that hemp is a “self-offsetting” crop. Generally, a farm (in the UK) emits a total CO2 equivalent of 3.1 MT of CO2 per hectare. Hemp, being a relatively low fertilizer and near-zero biocide crop requiring little management inputs, easily off-sets the carbon emission, due to cultivation and management, from the root mass remaining in soils. Thus, it is clear that hemp is an excellent crop for carbon capture and storage. Hemp should be the most preferred natural crop, even for largescale carbon capture and fixing dangerous greenhouse gas CO2, significantly mitigating devastating climate change effects.

4.2.4

Phytoremediation of Heavy Metal Contaminated Soil

Linger et al. (2002, 2005) have studied the potential of hemp for phytoremediation of heavy metal contaminated soil in detail and found that hemp can phytoextract heavy metals like cadmium (Cd) in moderate quantities. For example, hemp could extract ca. 126 g Cd per ha per crop cycle (in 3–4 months) compared to the Thlaspi caerulescens plant’s capacity of ca. 2000 g Cd per Ha per year. If we consider at least two crops a year, hemp can extract ca. 250 g Cd per Ha per year, which is one-eighth (12.5%) of Thlaspi caerulescens. However, unlike T. caerulescens, hemp thrives well under natural conditions and does not need extensive fertilizers, attention, biocides, and time- and money-intensive control for optimal growth. Further, T. caerulescens offers nothing of any commercial value, whereas hemp offers significant industrial uses. Since the heavy metals, after phytoextraction, are distributed in all parts of the hemp plant, thereby restricting its use for direct human consumption in food (seeds and leaves) and clothing as the concentration of heavy metals present in these parts exceeds the recommended limits (Linger et al. 2002). However, both bast fibers and hurds can be used as raw materials for bio-composites and construction materials, including hempcrete, as the metal contamination does not adversely affect the fiber quality. Hence, hemp offers an ideal solution for the phytoremediation of heavy metal contaminated soil economically and profitably.

4.2.5

Waste and Marginal Land Utilization and Its Reclamation

Wastelands in India and many countries are not suitable for agriculture or forestry for various reasons. While wasteland is not being used for revenue purposes, marginal land is related to the quality or non-availability of other crop production factors such as water in adequate quantity, where regular crops cannot be produced profitably. A considerable part of such lands can be used for hemp cultivation by making a

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suitable policy framework. As mentioned above, hemp tends to break the soil deep if the water table is low as the hemp root system adapts quite well to soil conditions. After few crop cycles of hemp, the land could become more suitable for other crops, thus reclaiming waste and marginal lands.

5 Uses and Applications of Industrial Hemp Hemp can boast of having few significant firsts to its credit, being it first woven cloth ca. 8000 BCE (Herer 2007), first paper ca. 500 CE (Abel 1980), earliest domesticated plant ca. 10,000 BCE (Abel 1980; Small 2017), and also among earliest renewable ingredients in construction materials ca. 500 CE (Singh et al. 2018). Based on archaeological, anthropological, philological, economic, and historical literature about hemp, it is generally agreed that from 1000 BCE until 1883 CE, cannabis (hemp /marijuana) remained the most prominent agricultural crop on Earth. Among thousands of products, some include fiber, fabric, lighting oil, paper, incense, food, and medicines (Herer 2007). Thus, it can be said that there is no other plant that can match hemp/cannabis for its vast canvas of applications for humans for ages.

5.1

Traditional Uses of Hemp

Hemp/cannabis has been used for nutrition, medicine (Russo 2005; Chaturvedi and Agrawal 2021) on the one hand, and for its fiber (clothes, bags, ropes, paper, animal bedding, etc.) and also for shelter as stalk/hurd can be used as green building/ construction materials and also for composites, apart from renewable energy, on the other hand (Abel 1980; Karus 2000; Small and Marcus 2002; Small 2017; Karche and Singh 2019). Thus, every part of the hemp plant, flowers, leaves, seeds, and roots has several economic uses. Table 1. summarizes the basic uses of the hemp plant. Karus (2000) reported that the usage of the hemp fiber in the European Union in 1999 was around 26,821 MT, where specialty pulp products like cigarette paper, banknotes, technical filters, and hygiene products constituted ca, 87%, followed by composites for autos (6%). The contribution towards construction and thermal insulation materials was 4% and for textile ca. 1%. All other minor usage was limited to ca. 2% (Fig. 3).

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Table 1 Hemp plant parts and their various applications, along with demand drivers and demand disruptors Primary produce Plant part) Flower and leaf

Hemp products CBD, other cannabinoids

Applications Medicines (health care)

Seed

Seed oil

Confectionary, cosmetic oil

Seed

Highly nutritious food and food supplements For all possible usages

Bast Fiber (Phloem) (Long, strong and very durable, less ligneous)

Wood/Hurd Fiber (Xylem) (Small, more ligneous fibers)

5.2

Paper

Demand driver Illness, life Style

Nutritional food

Ecology (it saves on cutting trees). Growing trees takes years, while hemp grows in months Four times stronger than cotton, water, and pathogenresistant fiber

Cloth/bags/animal bedding, etc.

For all possible usage of clothes and fibers

Particle BoardsLaminates

Furniture and furnishing

Housing and office

Hemp Concrete (hempcrete). Anti-insect plaster

Housing and other buildings

Ecofriendly housing, biodegradable, can reduce energy inefficient mining, can be grown near demand centers

Demand disrupter Legality if flower & leaf have >0.3% THC, psychoactive Regulatory policies for industrial hemp agriculture Regulatory policies for industrial hemp agriculture Other pulp making plants used in papermaking and their production need for forest conservation Cotton and synthetic cloth production and their socio-economy aspects Regulatory policies for industrial hemp agriculture Regulatory policies for industrial hemp agriculture

Innovative Applications of Hemp Fibers

Hemp fibers have been the major product of the hemp plant world over for ages. There are two types of hemp-stalk fibers. One, obtained from bast (phloem) and the second from hurds/wood (xylem). While bast fibers are pretty long and strong, the hurd fibers are shorter. The strength of the hemp fiber is very high ca. 4–10 times more than cotton, depending on the type and severity of treatment during fiber extraction, such as retting, scutching, decortification, carding, spinning, etc. As the post-harvest treating severity increases to obtain softer yarn, mainly for textile, the strength of the hemp fiber decreases. While hemp fibers have traditionally been used for a variety of applications like clothes, fabric, ropes, sails, canvas, paper products,

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Agri-textile 1%

Construction / Insulation Materials 4%

Other 2%

Composite for Auto Parts 6% Specialty Pulp 87%

Fig. 3 Distribution of usage of hemp fiber in European Union in 1999 (after Small and Marcus 2002)

construction materials, etc., and are extensively covered in the literature (Small 2017; Karche and Singh 2019; Sorrentino 2021), in this section new and innovative applications of hemp fiber are discussed. The rapid technological advancement in various fields gives impetus to developing a variety of high technology applications of hemp products and composites, specifically hemp fibers. These innovative and green uses include carbon nanosheets, supercapacitors/batteries components, highend plastics and composites, 3D-printer filaments, oil absorbent materials, steel-like materials for cables, and construction materials (Karche and Singh 2019).

5.2.1

Super Capacitors and Energy Storage

Supercapacitors are long-life energy storage devices (batteries) used in various electronic and cordless gadgets and electric vehicle barking systems. Highperformance supercapacitors are generally made from graphene. The nanocarbon prepared from hemp seed oil/fibers is much cheaper and natural. Recently it has been reported that hemp supercapacitors exhibit higher efficiency and energy storage capacity compared to graphene. Wang et al. (2013) have prepared interconnected partially graphitic carbon nanosheets with 10–30 nm thickness) having an exceptionally high specific surface area (up to 2287 m2 g1) from hemp bast fibers by using simple hydrothermal carbonization followed by activation. The supercapacitor devices prepared from these hemp carbon nanosheets exhibit higher energy density than commercially available supercapacitors (Wang et al. 2013). This natural,

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low-cost, high-performance precursor has a great potential for various diverse applications apart from energy storage.

5.2.2

Additive Manufacturing (3-D Printing)

The 3D printing filaments are made from hemp bioplastic (HBP). The most common bioplastic, specifically for 3-D printing, is made from polylactic acid (PLA). However, hemp plastic filaments are ca. 20% lighter and stronger than PLA (Karche and Singh 2019). 3D printing is attracting increasing attention for industrial and domestic (household) applications. Consumers can produce customized objects in their homes using fully natural HBP prepared from hemp waste in a sustainable way.

5.2.3

Hemp fibers as Replacement of Harmonic/Spring Steel Cables

Since hemp fibers are very strong, the flexible cable nets prepared from hemp fiber were comparable to commonly used harmonic steel cable nets under slow and permanent load response (Viskovic 2018). A comparison of the performance indicators like weight ratio, Young’s modulus, stress limit weight between hemp and steel cable nets suggested that the hemp material is more efficient than steel from the view pony of weight/Young’s modulus ratio (i.e., ca. 2150 for hemp and 2100 for steel) as well as of the stress limit/weight (i.e., ca. 20.2 for hemp and 15.3 for steel) (Viskovic 2018). Further, hemp material is lighter than steel with comparable or better performance, clearly offering an eco-friendly and more sustainable alternative to metals like steel for specific applications.

5.2.4

Anti-insect Plaster for Heritage Conservation

Recently, Singh et al. (2018) have found out the presence of hemp in the plaster of ca. 1500–2000 years old Allora caves in India. It is quite interesting to note that while in the Allora caves, no damage to the paintings was caused due to the common insect activity compared to Ajanta caves, where ca. one-fourth of the paintings had been lost due to insect activity (Karche and Singh 2019). This conservation in Allora caves in India was attributed to the combination of hemp (Cannabis sativa) in mud and lime mortar. Since cannabis has insecticidal/antimicrobial activity (Chaturvedi and Agrawal 2021), along with Allora’s findings. It opens up a new innovative application of mixing hemp oil/hurd in paintings/plaster of heritage mural conservation in India and elsewhere (Singh et al. 2018). In addition to the applications mentioned above, there are other upcoming products made from hemp. Some of these include various CBD and hemp seed oil infused eatables and drinkables, oil-absorbing carpet, fireboard, nail polish, jeans, surfboards, jewelry, specialty paper (for banknotes, cigarette paper, etc.), sanitary

Industrial Hemp for Sustainable Agriculture: A Critical Evaluation from. . . Fig. 4 Major products of Hemp (Cannabis sativa)

Animal Feed / Bedding

Textiles

Body care/ Cosmetics

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Paper Products Green Composites Construction / Hempcrete

Food / Nutraceuticals Medicines

Carbon Fibre

Cannabis sativa Main Products napkins and diapers, hemp eyewear bags, masks, canvas, sneakers, biofuels, etc. (Vivek 2019; Karche and Singh 2019; Naithani et al. 2020; Small 2017). The global market size of industrial hemp products has been estimated at USD 4.71 billion in 2019 and is expected to grow at a healthy 15.8% CAGR (Grand View research 2020) during 2019–2027. The main growth drivers of hemp demand include hemp oil, food and beverages, personal care, and hemp fibers for auto components, textiles, and construction, mainly in the Asia-Pacific region. The increasing demand for natural, green, and eco-friendly oil paints, varnishes, coatings, and solvents is expected to increase in the near future. Similarly, the demands for sustainable and eco-safe fuels, lubricants, inks, natural fabric/textile is also growing steadily. Theos demand is attracting increasing investment in the production of hemp-based consumer goods (Grand View Research 2020; Transparency Market Reports 2021). Fig. 4 summarizes the main products of hemp.

6 Issues and Challenges of Commercially Sustainable Hemp Farming As it is clear from the previous section, hemp, as a crop, demonstrates its agronomical plasticity and adaptability, ability to contribute towards mitigation of climate change, and its utility for renewable and green raw materials for industrially important green materials for economic viability. However, there are still few challenges faced by hemp as a sustainable crop, as discussed below.

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Legal Hurdles

While growing hemp for industrial purposes is essentially legal. However, the caveat is that any part of the plant should not have a THC content of more than 0.3%, and the responsibility of proving it rests on farmers in India. It is worth noting that except for THC content, there is hardly any difference in the appearance between hemp and psychoactive marijuana plants. This is a unique challenge to hemp growers in India. The state compliance testing of THC can be economically and emotionally devastating for hemp farmers as authorities are mandated to destroy the crop with non-compliance of the statutory THC levels. This is a continuous source of stress, harassment, and a significant impediment to large-scale hemp cultivation and research activities. However, since social and, therefore, governmental acceptance of hemp is increasing with each passing day, it may be anticipated that a hemp farmer-friendly framework may be developed in due course. This would give an impetus to research and development in agronomical aspects, specifically in developing hemp seeds with no or less than 0.3% THC consistently. In fact, this market is emerging in the USA and some other countries.

6.2

Agriculture Inputs and Methods

Given the issues of growing populations, economic and geographical diversities, and its impact on ecology and their consequent unsustainability due to overemphasis on food grain crops and monoculture agricultural practices, there is a need for more diversified cultivation of multiple crops and crop rotation. For sustainability, primary production, supply chain, and intermediate processing, along with end-produce market and marketing echo system are all equally important following the principle of a chain being as strong as its weakest link. There can be various aspects and challenges in growing hemp sustainably. An understanding of an indicative matrix of inputs that go into hemp cultivation in terms of soil health, water, fertilizers and biocides, fuel, labor, and other overhead, including statutory expenses, is needed to examine the economics of hemp cultivation. These factors can be categorized concerning production, supply, and demand as enumerated in Table 2. Although the factors mentioned above are region-specific and may vary from place to place, some aspects are common and are being dealt with to producing all types of hemp farm products. Unless hemp’s market environment and government policies are based on rationale and evidence-based research and are not hostile to providing a level-playing field to hemp vis-à-vis other crops, hemp cultivation will continue to face challenges. Further, another barrier to developing a sustainable hemp industry is inadequate knowledge about hemp agronomy in the local environment and ecosystem toward producing product-specific high-yielding hemp varieties. For example, when attempting to produce CBD unless due care is exercised, a crop with a low quantity

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Table 2 Factors affecting various phases of Hemp Supply Chain (Adapted from Williams 2018) Parts of hemp supply chain Hemp production (Primary part)

Supply chain and intermediate processing of the produce (secondary part)

Product marketing to end-user/consumer (tertiary part)

Factors impacting the performance output Agronomical factors like seeds, soil, water, fertilizer, and pesticides and methods of agriculture for ideal produce, produce quality and produce mix output for optimum economic and agrarian sustainability Government policy or legal framework related to hemp agriculture and crop insurance Factors include primary produce marketplaces. Infrastructure at waypoints of the supply chain for storage and processing, administrative and trade management worked out for all possible products can be made out of hemp plant parts, creating a derived demand for hemp cultivation Existing industrial end-user products and consumer end-user products, trade management and legal framework, R & D, innovation, entrepreneurship, and new and emergent business models and markets

Outcome indicators Sustainable hemp cultivation with soil & ecological conservation

Minimum distance, ease of transport, and processing infrastructure

Demand enhancement and favorable policy framework, and ecosystem

of CBD may be produced, adversely affecting economic benefits. For CBD as the main produce, hemp cultivation requires more diligent care such as (i) precision irrigation, (ii) nutrient schedule (iii) feminized seeds aimed at producing high CBD with no or little (0.3% THC is considered marijuana; this threshold is more stringent (>0.2%) in the EU. The beginnings of the West’s renewed hemp industry began in the 1990s, as the EU and subsequently Canada began lifting restrictions. The USA legalized hemp research beginning in 2014, and passage of the 2018 federal farm bill established hemp as a legal crop in the US. Legalization has brought significant interest in hemp to both farm and business communities. Some of this enthusiasm may be based on the mythology surrounding the crop as a salvation for all that ails us (Cherney and Small 2016). However, despite such hyperbole, significant challenges must be addressed if the crop and its products are to fulfill this potential (Ely et al. 2022). The primary goal of this chapter is to consider some of the numerous possible applications for hemp. We won’t examine them all—given the claim of 25,000 uses (Anonymous 1938), that would be quite a chapter indeed!—but we’ll try to hit some of the high points. However, before we examine the possible uses, we will ponder the modern economy and how hemp may play a role in transforming it into something more sustainable than the current consumer-driven economic model.

2 Circular Economy: A New Model for Economic Systems and Sustainability Modern consumer economies are linear and built on a “take-make-waste” paradigm that places significant pressure on Earth’s resources (Dilley 2014; Schröder et al. 2020; Brydges 2021). Emerging models of a new circular (or doughnut) economy emphasize resource use efficiency and recycling materials to create job opportunities, conserve energy, and simultaneously decrease resource consumption and waste (Stahel 2016). Although the definition of a circular economy seems not completely defined or agreed upon (Kirchherr et al. 2017), it is clear that creating one will require significant change to existing economic structures. At the same time, doing

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so will offer great opportunities to address social and ecological challenges confronting humanity (Raworth 2017). We restate our recognition that a truly circular economy will address social, economic, and environmental outcomes, but for this chapter, we will confine our discussion of hemp and a circular economy to ecological or environmental quality attributes. Hemp has been viewed as a significant resource for the development of a circular economy. No other crop has such broad possibilities as a source of food, fiber, building material, biofuel, and functional therapeutic products (Pavlovic et al. 2019; Crini et al. 2020). Markets for hemp may encompass more than 25,000 products, ranging from textiles, clothing, rope, home furnishings, nutraceutical and industrial oils, cosmetics, food, and pharmaceuticals (Rupasinghe et al. 2020), many of which currently are derived from non-renewable resources. Using natural materials creates greater opportunities for recycling, re-use, or benign disposal (e.g., compost). The move to “circularity” will likely involve “upcycling,” in which spent materials are processed and repurposed (Bridgens et al. 2018). In the simplest case, upcycling hemp might involve collecting and converting residual biomass (i.e., stalks, leaves, and residual fibers) from hemp production to fabricate a wide array of commercial and industrial products. This can help address both economic and environmental concerns around resource scarcity and pollution associated with petroleum-derived product analogues (Chen et al. 2020). Advocates and supporters of hemp cultivation and utilization have promoted the crop as a sustainable and “circular” feedstock given its high annual biomass yield, a broad range of uses in manufacturing and construction, and its potential to sequester carbon through every stage of the plant’s life cycle (Nguyen et al. 2009; Luthe 2019). The potentially low environmental impacts of hemp cultivation and processing, along with its biodegradability, meet the three principles of the circular economy paradigm: design out waste and pollution, keep products and materials in use and regenerate natural systems (Ellen MacArthur Foundation 2019). Large amounts of carbon dioxide are sequestered during the hemp production cycle. Products generated from hemp biomass store carbon throughout their “life” until they are recycled or biodegraded and returned to the soil (Luthe 2019). The potential for hemp to have a broad impact will be a function of its ease of processing and wide range of potential product outputs (Nguyen et al. 2009). Processing may also require fewer toxic chemical inputs than wood-based products (Salem et al. 2021). Furthermore, residual stalks and leaves from grain or cannabinoid production can be harvested or collected as a “captured resource” at other processing stages. Indeed, as we have noted, the hurd fibers previously considered a waste product from bast decortication have increasingly been viewed as a valuable co-product for various uses (Luthe 2019; Rupasinghe et al. 2020). Hemp bast fibers and hurd can be used to produce a wide array of products for a circular economy, including building materials, paper, textiles, furniture, and biofuels (Schluttenhofer and Yuan 2017; Crini et al. 2020; Tulaphol et al. 2021). The considerable cellulose content of hemp’s bast and hurd fibers (55–57% and 40–48% respectively; Stevulova et al. 2014) lends itself particularly well to such products. Hemp hurd has also been used for environmental and agricultural

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applications, including mulch, animal bedding, adsorbents for water treatment, phytoremediation, and air and oil filtration (Tulaphol et al. 2021). The broad application of hemp plant material to numerous products with significant ecological, industrial, and societal value and with substantial capacity for upcycling suggests hemp has significant potential as a key crop in a future circular economy (Luthe 2019), provided it can be cost-competitive. Given the numerous opportunities to improve hemp agronomic and processing systems, there is strong reason to believe that its production can and will increase. As it does, corresponding prices will fall, stabilizing the market (Dhondt and Muthu 2021a) and spurring greater investment and use. With a sense of optimism about the crop’s future and role in sustainability, we now turn our discussion to some of its possible uses for a sustainable future.

3 Hemp as A Source of Sustainable Fibers and Biomass For centuries, hemp has been grown for its strong, durable fibers, which were used to produce ropes, paper, and rough “homespun” garments (Van Eynde 2015). Certainly, societies have utilized other fiber sources, but among bast crops, hemp has one of the highest strength-to-weight ratios (Liu et al. 2015; Papadopoulou et al. 2015), which made it an important commodity for pre-industrial societies. However, hemp fabrics generally were coarser and less desirable than those from other natural fibers such as cotton, flax, silk, and wool (Allegret 2013). The invention of Eli Whitney’s gin eased the constraints for processing cotton, leading to that crop’s rise and hemp’s decline for use in textiles manufacturing (Johnson 2014). Subsequent inventions (e.g., the steam engine), market changes (e.g., cheap imported and synthetic fibers), lack of mechanization, and legal restrictions (the Marihuana Tax Act and Controlled Substances Act) all contributed to the decline in hemp production, making it unsustainable in the twentieth century (Fike 2019).

3.1

Fabrics

The West’s re-exploration of hemp’s potential as a fiber and fabric crop is partially due to society’s recognition of the substantial environmental costs associated with cotton production, textile manufacturing, and the high resource use (especially water) by the fashion industry more generally (Niinimäki et al. 2020). Water use and contamination are primary concerns for both cotton fiber production and processing (Chapagain et al. 2006; Khatri et al. 2015). Irrigation is standard practice for over half of worldwide cotton fields and over 70% of all cotton produced (Bevilacqua et al. 2014; La Rosa and Grammatikos 2019). The production benefits achieved with irrigation are countered by environmental concerns that include water table depletion, soil salinization, and significant pesticide use, leading to human

Cannabis/Hemp: Sustainable Uses, Opportunities, and Current Limitations Table 1 Comparison of input and output in hemp fiber and cotton fiber production system (Duque Schumacher et al. 2020)

Variables Seed cost ($/ha) Fertilizer cost ($/ha) Water cost ($/ha) Pest control cost ($/ha) Total costs ($/ha) Final fiber yield (t/ha)

Hemp 573.20 187.17 1372.11 NR 2132.48 1.00–5.00

63 Cotton 218.98 135.50 2172.08 263.60 2764.87 0.80–0.93

NR not reported

health issues, particularly in developing countries (La Rosa and Grammatikos 2019). Finding alternative natural fiber sources that do not have such sustainability challenges is thus a key driver for promoting hemp fiber production (Bevilacqua et al. 2014). Hemp has substantial potential as an alternative (or complement) to both natural and man-made fiber sources—particularly cotton, which represents 40% of the fiber market (Bevilacqua et al. 2014) and has limited potential for further crop production (Muzyczek 2020). Adding hemp to the mix—either as an alternative fiber source or by literally making cotton-hemp blends—offers an opportunity to reduce the large input demand associated with cotton textiles and thus increase the clothing industry’s sustainability (Duque Schumacher et al. 2020). Hemp is touted as using resources more efficiently and cost-effectively (Table 1) while producing higher fiber yields than cotton (Duque Schumacher et al. 2020). Considered too rough in pure form, further processing and blending can improve the qualitative features of hemp fiber and its resulting fabrics (Kozlowski et al. 2006; Kostic et al. 2008; Sauvageon et al. 2018; Moussa et al. 2020). Also, as with other natural fibers, more work is needed to reduce the environmental effects of chemicals used to dye hemp fabric (Dhondt and Muthu 2021b). Thus, without favorable resolution of these issues, there is perhaps the risk that the costs and impacts of processing may reduce the environmental benefits of hemp production and use.

3.2

Sustainable Building and Manufacturing

Hemp’s potential relevance to a sustainable farm economy is directly tied to its value as a source of sustainable, renewable materials for the broader economy. A chief use among these may be as a building block for more sustainable construction industry because of its scale and significant carbon footprint. Energy uses, and losses of residential and commercial sectors combined account for about 40% of total US annual energy consumption (EIA 2021). As well, the footprint of the global building stock is expected to nearly double from about 230 billion m2 in 2020 to more than 480 billion m2 in 2060 (Architecure2030.org n.d.). Hemp could play a significant role in reducing the building industry’s carbon footprint, given its potential as a carbon sink when “locked” into building materials.

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Hemp is one of many natural materials being used for sustainable building and manufacturing in the construction industry. Both bast and woody core (called “hurd” or “shiv”) fibers can be utilized to create a wide variety of building products. We will describe a few below and recommend readers seeking a more extensive review of hemp-based construction products consult additional reviews (Crini et al. 2020).

3.2.1

Hempcrete and other Bio-Aggregates

Hempcrete (also called hemp-lime) products are of increasing interest for building construction (Fig. 1). Hempcrete consists of hemp hurd fibers mixed with lime (used as the binder) and water, and it is perhaps the best-known hemp-based building product. As with concrete, the mixture is blended before pouring into a form and allowed to cure. Hempcrete and similar materials can be used to create a variety of building products, including bricks, natural mortar, thermal plaster, and thermal screed for flooring (Radogna et al. 2018). As described above, hemp-based construction materials have low-embodied energy, with each kilogram of hemp hurd sequestering roughly 1.6 to 1.8 kg of carbon dioxide (Jami et al. 2018). In theory, hempcrete could even have a negative carbon footprint if waste lime captured from other industries could be used as the mineral binder (Jami et al. 2018). Aggregates generated from biologically-based resources have garnered increasing interest because they can sequester carbon and have numerous suitable building properties (Stevulova et al. 2014). Successful bio-composites and bio-aggregates require strong fibers with good adhesion between the fiber and the binding matrix to augment their performance (Stevulova et al. 2014). Hemp fibers are increasingly

Fig. 1 A hemp house under construction. Hempcrete is poured into forms (top insert) around the building’s structural components. After a layer is set, the forms are removed and shifted upwards. Colored bands in the hempcrete reveal where the layers were poured (bottom insert). Photos courtesy of Carol Brighton

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used to reinforce concrete, in part because they enhance the flexural and tensile strength of the composite material, limiting cracking (Tulaphol et al. 2021), and combining hemp with hydraulic lime can generate mortars with enhanced insulative and flexural properties. Also, adding ground hemp flower to concrete mixtures can delay the hydration of cement; as a powdered retarder, hemp flower has performance similar to conventional chemical admixtures used to control concrete setting (Guo et al. 2020). Binders (which range from clays to lime) serve to aggregate the hemp hurd and play an integral role in enhancing its strength, durability, hydroscopicity, pyrolysis threshold, resistance to insect damage, and acoustical and thermal performance. (Arizzi et al. 2015; Florentin et al. 2017; Jami et al. 2018). Hemp can absorb most of the water existing in the binder matrix. Some further additions of material and processing have been suggested to improve the production and curing procedures, influencing the structural performance of lime-hemp mortars (Arizzi et al. 2015). Generally, hempcrete and related products do not match the compressive strength of conventional concrete. However, along with reinforcing concrete, hemp hurd and hemp bio-composites have demonstrated potential as thermal and acoustical insulators in residential, commercial, and industrial applications (Nguyen et al. 2009; Jami et al. 2018; Fernea et al. 2019; Hussain et al. 2019; Santoni et al. 2019; Charai et al. 2021). Hemp hurd can effectively be used by itself as thermal and acoustical insulation within load-bearing walls, and sound absorption can be enhanced in hemp composites through adjustments to pore number and size and geometry of the final material (Benfratello et al. 2013; Degrave-Lemeurs et al. 2018; Fernea et al. 2019). If built properly, structures with hemp or other natural fibers may improve indoor environments because of the material’s transpirability and hygroscopicity (Célino et al. 2014; Arizzi et al. 2015). These attributes help mitigate indoor moisture and improve the environment of the indoor living space (Arizzi et al. 2015). However, the use of natural fibers in building structures can pose a risk with improper design. The fiber has hydrophilic surfaces that can result in weak bonding and high moisture uptake (which leads to swelling), leaving the material vulnerable to microbial attack (Liu et al. 2017). Trapped moisture, in turn, can increase mold presence and lower air quality (Kymäläinen and Sjöberg 2008). Additives or fiber pre-treatment, suitable binders, and proper construction techniques are needed to optimize inclusion rates and ensure the living space’s sustainability (Kymäläinen and Sjöberg 2008; Benfratello et al. 2013; Arizzi et al. 2015; Liu et al. 2017).

3.2.2

Biocomposites

Similar to bioaggregates, composite materials are formed by combining two distinct materials, such as a polymer resin matrix and reinforcing fibers. The resulting material has better functional properties than the individual components (Ramakrishna and Huang 2016). Composite materials have been used in numerous industrial applications, including automobiles, packaging, and construction (Błedzki et al. 2012);

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although historically, the components have been synthetically derived. Biologicallybased “biocomposites” are typically made with natural fibers embedded either in a natural or synthetic polymer. These materials are increasingly looked upon as an alternative to synthetic composites, given their inherently lower production costs and renewable, recyclable, and biodegradable nature. Composite polymers derived from petrochemicals have been predominant over the last several decades, given the relatively inexpensive cost of plastics derived from crude oil. More recently, the use of biocomposites has increased by about 50% annually in the automotive industry, as new legislation has compelled automobile manufacturers to recycle and re-use expended materials (Błedzki et al. 2012). Increased ecological and environmental awareness among consumers, too, has generated an increased market for products based on regenerative raw materials (Błedzki et al. 2012). As a result, standardization of biomaterials used in various products is being determined (Błedzki et al. 2012). Hemp is considered one of the best raw materials for biocomposites production for the nascent sustainable bioeconomy (Karche and Singh 2019). Hemp-derived biocomposites take various forms, e.g., foams, film membranes, and hemp composites have great potential to replace glass fiber (Marsh 2008). Material properties include significant strength, stiffness, and durability, and the products also are lightweight and biodegradable (Manaia et al. 2019). Natural fibers and their composites could find uses for a number of industries (Pappu et al. 2019), but they are of particular interest to the automobile industry, which is working to address its environmental impact (Anonymous 1938; Manaia et al. 2019; Coman-Enescu 2020). Hemp fibers are an excellent source for producing insulating materials and interior panels for cars (Schultes 1970; Schultes et al. 1974; Holbery and Houston 2006), and after a decades-long hiatus (Petrović et al. 2004; Akampumuza et al. 2017); some auto manufacturers are once again exploring their use in exterior components (Perkins 2019; Porsche 2020). Such uses could be extended into other sectors as well (Karche and Singh 2019). Despite the potential for varied industries to use hemp bio-composites, several challenges associated with these materials first must be addressed. Fiber susceptibility to microorganisms, its hydrophilic nature, inadequate thermal stability, and variable fiber quality (a function of plant genotype, fiber harvest methods and timing, and post-harvest processing methods) must be addressed to support broader adoption (Manaia et al. 2019). Many of these issues may be addressable if new and targeted pre-treatments can be developed that improve fiber surface properties and optimize the performance of the end product composites (Liu et al. 2017).

3.2.3

Other Building Materials: Insulation, Particleboard, “Lumber,” Flooring, and Fiber Mats

Several companies in Europe (Lekavicius et al. 2015) and a few in North America now market hemp-based insulation products derived from bast fibers. Research on these products is somewhat limited, but generally, the materials get acceptable marks

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for thermal insulation and with good acoustic insulation performance (Kozłowski et al. 2008; Kymäläinen and Sjöberg 2008; Mirski et al. 2018). As noted above, the “breathability” of hemp-based products contributes to better indoor environmental conditions (Arizzi et al. 2015). However, proper harvest, handling, and manufacturing processes are needed to ensure these products do not become a source of mold or other microbial contaminants (Kymäläinen and Sjöberg 2008) and additives are needed to improve handling and reduce flammability. Several researchers have explored hemp as an alternative material for particleboard used in furniture manufacturing and construction. The sector has a global value of USD 21 billion (Imarcgroup.com n.d.), presenting significant market and sustainability opportunities. The suitability of hemp-based boards is highly affected by process (Mirski et al. 2018). Thickness, water swell, and fire retardancy are primary concerns (Battegazzore et al. 2018; Kremensas et al. 2021). However, with appropriate resins or other treatments, boards derived from hemp or other farm residues can be manufactured that comply with ANSI standards and have better mechanical performance properties (Sam-Brew and Smith 2017). Efforts also have been given to developing boards with biobased resins (soy in this case) with some success (Alao et al. 2020), and binders may be unnecessary with appropriate pre-treatment (Tupciauskas et al. 2021). Interestingly, some cultivars were better suited for the board construction, likely due to differences in chemical composition (Tupciauskas et al. 2021). Adding hemp fiber mats to particleboard enhances their strength properties, making them stiffer and stronger (Sam-Brew and Smith 2015). Utilizing hemp in three-layered particleboards can decrease the density significantly (Schopper et al. 2009). Ongoing research and development will support new and innovative uses for hemp. HempWood® has developed innovative lumber and flooring materials that could make significant contributions to building sustainability and carbon capture (Fig. 2). The product is marketed as “20% stronger than oak and 100 times faster to grow.” Once (or as) the building is constructed, long fibers may find a place in the construction process as biodegradable fiber mats used for landscaping and soil protection (Fig. 3). Landscape fabrics and mulches support sustainability by reducing erosion (Theisen 1992; Prats et al. 2016), suppressing weeds, and have the added feature of biodegrading within several months (Miao et al. 2014).

3.2.4

Substrate for Mycelium-Based Composites

In one of the more recent advances in hemp applications, the hemp plant fibers are being given serious consideration as a feedstock/substrate for mycelium-based composites (Lelivelt et al. 2015). These have applications both within and beyond construction. Both hemp and mycelium composites have significant potential in thermal and acoustical absorption performance (Pelletier et al. 2013; Fernea et al. 2019; Schritt et al. 2021). The hemp works well as a growth medium for the

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Fig. 2 Hemp has potential as a wood replacement for finding use as lumber and flooring. Photos courtesy of HempWood®

Fig. 3 Hemp fibers work well when used as biodegradable mats for erosion control and weed suppression (inset). Photo courtesy of BioComposites Group

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Fig. 4 Mycelium growing in inoculated hemp substrate (left). Mushrooms growing from hemp substrate (middle). Mycelium-based composite formed using hemp substrate (right). Photo credit: Matthew Reiss

cultivation of a wide variety of gourmet and functional mushrooms due to its significant lignin, cellulose, and hemicellulose content (Dawidowicz et al. 2018). Through a solid-state fermentation process, hemp is quickly aggregated by the mycelia (vegetative fungal biomass) of white-rot fungi (lignin-degrading higher fungi), where it is bound in a lightweight network of filamentous fungal tissue (Fig. 4). Mycelial composites grown with hemp show great promise for producing lightweight, alternative natural insulation materials using resources that are renewable, quickly regenerative, and abundant (Elsacker et al. 2019). All residual parts of the plant can be used as mushroom culture media (Zhao et al. 2021). Deploying residual hemp biomass as a substrate for mycelium-based composite fabrication can not only render a range of composite materials (Elsacker et al. 2019) but upcycles hemp residues and does so in an ecologically regenerative manner. Mycelium-based composites use the vegetative body of white-rot fungi to partially digest and aggregate the hemp into a lightweight, dense bio-composite material, growing on the hurd fibers of the hemp plant (Elsacker et al. 2020). Various fungal species of the genera Pleurotus, Ganoderma, Trametes, and Coriolus have significant potential for creating acoustical panels and thermal insulation products derived from a combination of mycelium and hemp shive (Butu et al. 2020). More thorough research and testing on the mechanical properties of these materials will continue to determine which applications are best suited for these bio-composites (Lelivelt et al. 2015.

3.3

Hemp-Based Paper

Hemp’s reintroduction in the West largely began with manufacturing specialty papers with high-quality pulp, attributing to high tensile strength (Crini et al. 2020; Amode and Jeetah 2021). Hemp papers are more stable and durable over time—though their cost of manufacture is several-fold greater than for wood-based papers (Ranalli and Venturi 2004; Crini et al. 2020). Given their superior quality but greater cost, hemp papers from bast fibers find use primarily in specialty products

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such as cigarette papers, bank notes, filters, and Bibles or other specialty books (Yao et al. 2017). Adopting hemp for paper might appear a good place to improve sustainability, but whether it can be a serious competitor to forest inputs remains a question. The pulp and paper industry currently sources nearly 90% of its raw materials from trees (Shatalov and Pereira 2006; Danielewicz and Surma-Ślusarska 2011; Edyta et al. 2015; Cherney and Small 2016). The industry estimates that two-thirds or more of the energy inputs for paper production are met with renewable energy (Internationalpaper.com n.d.; AF&PA 2020), and US paper recycling rates are approaching 65%, representing a relatively high degree of existing system circularity (Leblanc 2018). Production costs and limited available markets present additional challenges for hemp paper. Bast fibers, which contribute significantly to paper strength, require added processing, increasing costs (Crini et al. 2020). Incorporating low-value hurds into paper products may be an option for increasing hemp usage, particularly for tissue paper and paper towels (Naithani et al. 2020). However, such sanitary and household products make up about 15% of the US paper product market size, versus about 50% for packaging paper (Grandviewresearch.com 2020); products derived from hemp hurd currently represent 5% of the total global paper supply (Salem et al. 2021). For a nascent hemp industry, any large-scale production system (whether hempcrete, particle board, composites, or paper) must contend with logistics and storage, which add further to hemp costs (Crini et al. 2020). Logistics can play a critical role in the function and profitability of annual harvest systems, given the demands of moving large quantities of bulky feedstocks from the field to the facility (Fike et al. 2007; Cundiff et al. 2009). In contrast, trees are “stored on the stump,” which provides a great deal of logistical flexibility. Trees also require fewer inputs, more generally, whereas annual crops must be grown and gathered within a seasonal harvest window to reduce yield and quality losses. Although system comparisons are limited, a life cycle assessment comparing hemp with eucalyptus for paper production suggested hemp would have greater environmental impacts given the greater fertilizer and processing inputs required (Da Silva Vieira et al. 2010).

3.4

Hemp as a Bedding

One of hemp hurds’ initial uses was as a bedding for horses, livestock, and pets (Fig. 5; Small and Marcus 2002; Karus and Vogt 2004). Hemp hurds are reportedly several times more absorbent than traditional wood or straw bedding options (Small and Marcus 2002; Carus and Sarmento 2016), but there is little direct evidence of this in the literature. In one of the few studies available, hemp was less preferred as a horse bedding than pine-based materials (Wolfzorn et al. 2015), but it is unclear how the material was processed. Hurds also may cause less irritation (from dust or allergens) than some wood fibers (Small and Marcus 2002), and they can reduce

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Fig. 5 Hemp is being used as a bedding for horses, poultry (top inset), and pets (bottom inset). Photos courtesy of Marty Phipps, Old Dominion Hemp

microbial growth relative to chips or shavings from some (but not all) tree species (Yarnell et al. 2017). Odor suppression may be greater with hemp than other biological materials, but data on ammonia absorption appear mixed and a function of processing (Airaksinen et al. 2001; Fleming et al. 2008). Hemp bedding is generally more expensive than sawdust or shavings. Still, materials with better function (i.e., less dust, greater absorption, etc.) that reduce both the inputs and labor needs may warrant greater cost relative to more traditional bedding materials— and costs will likely decline when and if fiber hemp production expands.

3.5

Hemp as Sorbent Material Beyond Bedding

Beyond its potential value as bedding, hemp derivatives, both fiber and protein powder, may contribute to sustainability as a sorbent of environmental contaminants in water. In contrast, hemp plants may serve as a means to decontaminate soils (see next section). For several heavy metals, bio-sorption both with flax (Linum usitatissimum) and hemp-based ‘felts’ were efficient, rapid, and unaffected by pH between 4 and 6 (Mongioví et al. 2021). The utility of such materials is augmented by the fact that they can successfully go through several sorption/desorption cycles

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with little change in efficiency (Tofan et al. 2020). Carbonized fibers also have been developed for metals and pesticides extraction and analysis (Pejic et al. 2011; Vukcevic et al. 2012; Vukčević et al. 2014). Readers interested in detailed studies of the hemp uses, and sorption processes may read Morin-Crini et al. (2019) to explore this topic further. Hempseeds, too, have been used to remove man-made contaminants from groundwater (Turner et al. 2019). Calculated on a protein basis, the protein powder from hempseeds has proven more effective than other vegetable protein sources at removing perfluoroalkyl and polyfluoroalkyl substances, so-called “forever chemicals” (Turner et al. 2019). These authors reported >98% removal after an hour of contact time and indicated that hemp protein powder is likely to become an effective means of remediating contaminated waters. In an agricultural context, hemp may also prove useful as a resource for improving salt-contaminated soils (Cosarca et al. 2017). Adding hemp hurd to growing media reduced salt effects as measured by increased plant growth in a pot study (Cosarca et al. 2017). However, high application rates (1% of media) may limit feasibility at the field scale.

3.6

Contaminant Tolerance and Phytoremediation

As a crop (rather than a product), hemp has potential sustainability contributions to restore productivity or function to degraded soils. Environmental pollutants (i.e., heavy metals, pesticides, radionuclides, etc.) can enter food webs, eventually accumulating in plants and animals and posing a danger to those who may consume them (Edgar et al. 2021). Growing non-accumulator crops on contaminated sites is one means of restoring a site’s function, but removal is necessary to restore healthy ecosystems. Methods traditionally used to remove toxins are costly and environmentally invasive (e.g., soil excavation), whereas phytoremediation can be a sustainable, environmentally friendly, and economically viable alternative (Rheay et al. 2021; Wu et al. 2021). Hemp productivity has been tested in the presence of several contaminants, including hydrocarbons and heavy metals. Hemp plants can tolerate polyaromatic hydrocarbons and soils contaminated with oil (Campbell et al. 2002; Timofeeva et al. 2020). In the latter case, however, seedling germination and emergence were reduced dramatically (Timofeeva et al. 2020). Still, such data indicate that hemp cultivars might be selected based on such capacity. To date, more research has been given to understand hemp’s ability to tolerate or even absorb and accumulate heavy metals. Some studies suggest that heavy metals may have a limited effect on plant growth (Shi and Cai 2009; Ahmad et al. 2016; Husain et al. 2019), although these responses vary by metal species (Luyckx et al. 2021) and plant cultivar (Shi et al. 2012), and are mediated by other factors such as soil fertility (Deng et al. 2021). The potential for dual-purpose crops that both take up metals and are processed for industrial purposes has been questioned, given the

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presence of metal contaminants in fibers (Linger et al. 2002). However, this may depend on end-use and process. Some have suggested integrating phytoremediation with bioenergy production as a sustainable option to utilize contaminated biomass (Edgar et al. 2021; Rheay et al. 2021). In addition to industrial contaminants, hemp may have some capacity to sustain or regenerate the productivity of salt-affected soils. Several mechanisms may be involved in adjusting to salt stress (Cheng et al. 2016). Research evaluating crop type and management is needed as Hu et al. (2019) reported that grain varieties were less sensitive to salt than fiber types. Mycorrhizae also have been implicated in supporting plant growth and reducing Na+ uptake relative to untreated plants (Tadayon 2014).

3.7

Hemp Biomass for Bioenergy

Current energy demand primarily depends on burning fossil fuels, a major source of carbon emissions or greenhouse gases (Parvez et al. 2021). Climate change concerns and depleting fossil fuel stores have increased interest in the growing role of bioenergy, an alternative and sustainable energy source that may serve in future energy production (Reid et al. 2020). Biomass, the majority contributor to bioenergy production, makes up 70% of global renewable energy generated (Reid et al. 2020). Hemp biomass makes up nearly 52% of the whole plant dry matter (Matassa et al. 2020), therefore, increased hemp products entering the market results in increased hemp biomass residues (Ji et al. 2021). Hemp biomass has been evaluated and could be successful for any number of bioenergy processes (i.e., biodiesel, biogas, bioethanol, and solid biofuel production; Rheay et al. 2021). Hemp seed oil used for fuel achieves conversion rates up to 97% biodiesel and can be burned with fewer emissions than traditional diesel (Parvez et al. 2021). Biogas and ethanol can be produced from wet and ensiled hemp biomass (Adesina et al. 2020). Perennial species such as Miscanthus are often more sustainable bioenergy options with high biomass production and reduced yearly emissions. However, the similar energy output of 156 GJ ha
1 year
1 and farmer flexibility to add hemp to a crop rotation makes it a competitive annual species (Finnan and Styles 2013). Direct combustion in residential wood stoves allows hemp to be processed into dense pellets with superior energy content to wood (5.2 MWh/ton vs. 4.3 MWh/ton, respectively) (Young 2005). Although hemp has unique potential, similar systemic concerns (as with other bioenergy crops), including lack of processing facilities and poor farmer adoption, could limit its use and application. More research is needed to maximize energy production and ensure the crop’s economic feasibility for large-scale commercial bioenergy production (Ji et al. 2021).

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4 Hemp Grain as a Source of Sustainable Food, Feed, and Nutraceuticals Although most histories of hemp are constructed around the plant’s importance as a fiber crop, historical evidence points to its use and value as food and medicine (Fike 2019). As societies begin a re-exploration of the crop, food uses may again get top billing. Still, there is historical precedence for its use in industrial products such as paints, varnishes, sealants, and printing inks. It was even popular as an oil fuel for lighting before the nineteenth century (Small and Marcus 2002), and perhaps, if such a past is prologue, it may be suitable as a feedstock source for diesel biofuel (Parvez et al. 2021). Hemp seed oils may also be suitable for industrial applications. The high degree of unsaturated fatty acids in hemp seed oil could make it a replacement feedstock for plastic production (Callaway and Pate 2009). This would provide a biodegradable and environmentally friendly alternative to petroleum-based plastics (Modi et al. 2018; Ghasemlou et al. 2019). Still, lack of efficiency and current production costs may limit hemp from extensive industrial use (Young 2005). Thus, as an instrument for improving sustainability in the broadest sense, hemp grain will play a more minor part than hemp fiber, given both its lower yields and smaller range of applications. The generally lower per-land-area oil yield compared with oilseed crops such as soybean (Glycine max), canola (Brassica napus), and sunflower (Helianthus spp.) will further put hemp at a competitive disadvantage unless the oil has value for its unique chemistry—and that is indeed the driver of the current interest in hemp grain.

4.1

Hemp Grain Nutritional Characteristics

A foundational grain in early societies, hemp fell from favor as a food resource as other grains were domesticated (Clarke and Merlin 2013). However, recent resurgent interest in hemp as food has arisen with the recognition that the crop has significant nutritional value and functional properties, particularly relative to other commodity grains. This has driven substantial growth in the global hemp seed market, which in one forecast is projected to grow more than 11% over the next several years (Fortunebusinessinsights.com 2020). In 2019, the global market for hemp seed was >USD 710 M, with almost 45% used for food and beverages; the market is projected to more than double to >$1.6 B by 2027 (Fortunebusinessinsights.com 2020). This increase is driven both by growing consumer awareness of hemp’s nutritional value and increased opportunities for companies to use hemp as an ingredient in foods, beverages, and personal care products as government restrictions to hemp fall (Fortunebusinessinsights.com 2020). The list and variety of hempderived products continue to grow as the awareness of hemp’s nutritional characteristics increases (Rupasinghe et al. 2020). Hemp seed constituents can be found in

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Fig. 6 Hemp “hearts” (far left) and (middle left) processed from whole seed. Hearts are cleaned and sorted with a shaker sorter (middle right). Hemp oil (square; far right) typically is extracted by cold pressing whole seed, leaving a pellet (circle) high in fiber and protein. Photo credit: John Fike

products ranging from flour and baked goods to “milk,” “butter,” and even beer (Crini et al. 2020). A hemp seed, technically an “achene,” comprises a hull surrounding a true seed (Ely et al. 2022). The true seeds contain the fatty acids, proteins, anti-oxidants, and other plant metabolites that make hemp a potentially powerful functional food. Seeds generally contain 25–35% fat, 20–25% protein, and 20–30% carbohydrates, along with several vitamins and minerals, although these differ by variety (Schultz et al. 2020). Environmental conditions further affect variability in seed development and quality (Farinon et al. 2020). Hemp seeds are primarily sought after for their unique fat content. Rich in polyunsaturated fatty acids, hemp seeds are a good source of α-linolenic acid and linoleic acids. They have a favorable ω6:ω3 ratio (Callaway 2004), ranging from about 2:1 to almost 5:1 (Schultz et al. 2020). Hemp seed is unique in that it is the only grain with gamma-linolenic acid, an ω6 fatty acid with anti-inflammatory qualities (Kapoor and Huang 2006; Farinon et al. 2020). About 75% of hemp seed fiber is concentrated in the hull, which is highly lignified (Schultz et al. 2020), and removing this component can be advantageous from a food products perspective. Dehulling reduces the overall fiber content, and the resulting “hemp hearts” have 40–50% fat and 30–40% protein (Wang and Xiong 2019; Leonard et al. 2020). Too, the dehulling process often leaves embryo fragments, thus increasing the fat and protein content of the residual hemp hulls (Fig. 6). To date, hemp seed oil has been the component of primary interest for human consumption, given its unique nutritional attributes and potential uses in personal care products. Hemp seed protein is composed primarily of the highly digestible

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globular proteins edestin and albumin and all essential amino acids in satisfactory ratios (Callaway 2004). The oils typically are cold-pressed, leaving a residual protein “cake.” Protein in the cake by-product ranges from 30% to 50% (Wang and Xiong 2019. Hemp seed cake can be further processed to produce concentrated protein isolates (Wang and Xiong 2019), useful as protein supplements in human diets (Fig. 6).

4.2

Hemp in Livestock Diets

The resurgent interest in hemp production has led to an interest in feeding hemp seed to livestock to increase the nutritional value of animal-based products (e.g., meat, milk, and eggs). However, industry growth has been slowed since numerous countries placed bans on feeding industrial hemp products to livestock. Safety concerns regarding cannabinoid contamination in livestock products remain the biggest hurdle for approving hemp feed for livestock (Sandison 2017). These restrictions are likely to fall as more regulators understand that seeds are not a source of cannabinoids and as societies reconsider their relationship with Cannabis more generally. Livestock generally tolerates whole hemp seed and hemp seed products quite well. The grain is an excellent source of protein and fat with unique, healthful fatty acid profiles, and feeding these products offers an opportunity to enhance the quality of meat, milk, and eggs (Mustafa et al. 1999; Silversides and Lefrançois 2005; Karlsson et al. 2010; Neijat et al. 2014). For a more in-depth review of feeding hemp grain, readers can refer to Chap. 6 in this book (Ely et al. 2022). As hemp seed production and processing expands, the development of an associated by-product feeds industry is likely to follow. In this context, livestock contributes to system sustainability by efficiently using upcycling typically unusable plant by-products as dietary ingredients (Oltjen and Beckett 1996). (Distiller’s and brewer’s grains from corn (Zea mays), middlings from wheat (Triticum aestivum), and meal and hulls from soybean processing represent but a few examples.) Hemp seed cake, a by-product of oil extraction, is a highly digestible alternative protein source for livestock diets (House 2021), and hulls from hemp hearts production can be a useful fiber source. Aside from the special case of hemp sprouts (Werz et al. 2014; Frassinetti et al. 2018) or perhaps seasoning, humans have little use for mature hemp as a food. The fibrous and woody core limits the potential use of the mature plant in livestock diets. However, possibilities still may exist to grow hemp as a forage crop (Stringer 2018). Pecenka et al. (2007) looked at the ability to ensile whole hemp plants with moderate success. In producer trials, hemp silage had a crude protein concentration of 19%, but results were unable to be replicated due to poor plant growth the following year (Duckworth 2000). Hemp grown for forage in a university trial had similar nutritional characteristics (17% crude protein). Still, the author concluded that its potential as an alternative annual forage would remain limited unless yields were improved (Stringer 2018). Hemp’s response to defoliation intensity or timing

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would be expected to affect both seasonal yield and nutritive value, but to our knowledge these factors have not been evaluated. Residual flowers and leaves from cannabinoid extraction may also have value as a by-product feed. However, initial analysis suggests that these will be fiber-rich and of limited nutritional value (Ates 2021). Based on the minimal data available, use of these by-products likely will be restricted ruminant and equine diets for animals with low nutritional needs.

4.3

Nutraceutical and Healthcare Products

Although reincorporating hemp into human diets does not improve sustainability in the general sense, it may at least be useful to an individual’s sustainability from a health perspective. As discussed, much of the interest in hemp as a food resource is based on its fatty acid profile benefits. Dietary ω6:ω3 fatty acid ratios less than 10:1 have been considered ideal for human health (Simopoulos 2001), and hemp is well below that (Callaway 2004; Dimić et al. 2009; Da Porto et al. 2015; Farinon et al. 2020). Several health studies have provided evidence of benefits associate with hemp consumption. Hemp seed oil improves symptoms associated with atopic dermatitis, including reducing dryness and itching (Callaway et al. 2005). It altered the composition and reduced the concentration of total plasma triglycerides, suggesting that consumption can enhance cardiovascular health (Schwab et al. 2006). Similarly, supplementing hemp seed oil altered fatty acid profiles of red blood cells, specifically increasing ω3 concentration (Del Bo et al. 2019), which is also related to improved cardiovascular outcomes. Hemp seed anti-oxidants, too, may serve to protect against the oxidation of fatty acids—both within the seed and the humans who consume them (Irakli et al. 2019). Hemp could be a promising food crop based on its highly nutritive makeup (Irakli et al. 2019). However, much of the literature comes to the familiar conclusion that more research is needed. Studies to determine effective dosages and identify suitable delivery matrices will be central to maximizing hemp seed oil’s effect on human health.

4.4

Cosmetics and Personal Care Products

Consumer interest in alternative, naturally sourced, and sustainable healthcare products is a driving factor behind the increased demand for hemp-based products (Karche and Singh 2019; Crini et al. 2020). Derived from seed oil and flower extracts, hemp oils and resins are used extensively in consumer products, including shampoos, topical oils, lotions, and balms (Da Porto et al. 2012; Gohad et al. 2021). Hemp seed oil, a natural emollient with moisturizing properties, is a good candidate

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for skincare ingredients due to its high concentrations of fatty acids and anti-oxidant potential (Crini et al. 2020). Cannabidiol (CBD) and other non-psychotropic cannabinoids extracted from hemp flowers are of growing use in the personal care and cosmetics industries because of their potential anti-inflammatory, anti-oxidant, and anti-acne properties (Martinelli et al. 2021). In addition, CBD exerts protective effects on the skin from ultraviolet rays (Gohad et al. 2021). Niche markets have also developed for hemp flower extracts’ use as a novel flavor or scent in food and cosmetic products (Menghini et al. 2021). However, we note that the oft-used term “CBD oil” is a misnomer, as concentrated flower extracts are resinous.

5 Conclusions The myriad of products and “services” that can be derived from the hemp plant include food, feed, fiber, bioenergy, medicines, building materials, bio-composites, phytoremediation, and more. Hemp will likely have the greatest positive impact on sustainable development if it can be harnessed as a source of renewable feedstocks for a broad array of building/construction and manufacturing materials. Such uses offer significant possibilities for the development of a circular economy. Hemp may have a less direct impact on sustainability as a source of nutrients and nutraceuticals. Still, these products, too, stand to make life better for human beings, given their excellent nutritional and nutraceutical profiles. Achieving greater sustainability through hemp production and utilization also will require development of sustainable crop production models that feed sustainable process systems for renewable and recyclable or upcyclable materials. Human ingenuity and creativity across agricultural and industrial platforms will be required to achieve hemp’s potential value to society. Product development across all domains, e.g., fibers, foods, feeds, and nutraceuticals, must be given to creating materials with broad commercial and consumer acceptability. Society, in turn, must demonstrate its interest in hemp-based sustainable products, as consumer demand will be the ultimate arbiter of the plant’s success as a sustainable crop.

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Tupciauskas R, Rizhikovs J, Brazdausks P et al (2021) Influence of steam explosion pre-treatment conditions on binder-less boards from hemp shives and wheat straw. Ind Crop Prod 170:113717. https://doi.org/10.1016/j.indcrop.2021.113717 Turner BD, Sloan SW, Currell GR (2019) Novel remediation of per- and polyfluoroalkyl substances (PFASs) from contaminated groundwater using Cannabis Sativa L. (hemp) protein powder. Chemosphere 229:22–31. https://doi.org/10.1016/j.chemosphere.2019.04.139 Van Eynde H (2015) Comparative life cycle assessment of hemp and cotton fibres used in Chinese textile manufacturing. University of Leuven Vukcevic M, Kalijadis A, Radisic M et al (2012) Application of carbonized hemp fibers as a new solid-phase extraction sorbent for analysis of pesticides in water samples. Chem Eng J 211–212: 224–232. https://doi.org/10.1016/j.cej.2012.09.059 Vukčević M, Pejić B, Kalijadis A et al (2014) Carbon materials from waste short hemp fibers as a sorbent for heavy metal ions - Mathematical modeling of sorbent structure and ions transport. Chem Eng J 235:284–292. https://doi.org/10.1016/j.cej.2013.09.047 Wang Q, Xiong YL (2019) Processing, nutrition, and functionality of hempseed protein: a review. Compr Rev Food Sci Food Saf 18:936–952. https://doi.org/10.1111/1541-4337.12450 Werz O, Seegers J, Schaible AM et al (2014) Cannflavins from hemp sprouts, a novel cannabinoidfree hemp food product, target microsomal prostaglandin E2 synthase-1 and 5-lipoxygenase. Pharma Nutrit 2:53–60. https://doi.org/10.1016/j.phanu.2014.05.001 Wolfzorn J, Porr S, Harding D et al (2015) Miscanthus and hemp as alternative bedding material for horses Wu Y, Trejo HX, Chen G, Li S (2021) Phytoremediation of contaminants of emerging concern from soil with industrial hemp (Cannabis sativa L.): a review. Environ Dev Sustain:1–31. https://doi. org/10.1007/s10668-021-01289-0 Yao Y, Jian-Bo Z, Hao W, et al (2017) Manufacturing technology and application of hemp cigarette paper with dense ash integration. IOP Conference Series: Earth and Environmental Science Yarnell K, Le Bon M, Turton N et al (2017) Reducing exposure to pathogens in the horse: a preliminary study into the survival of bacteria on a range of equine bedding types. J Appl Microbiol 122:23–29. https://doi.org/10.1111/jam.13298 Young E (2005) Revival of Industrial Hemp: a systematic analysis of the current global industry to determine limitations and identify future potentials within the concept of sustainability. Lund University, Lund Zhao H, Xiong H, Chen J (2021) Regional comparison and strategy recommendations of industrial hemp in china based on a swot analysis. Sustainability 13:6419. https://doi.org/10.3390/ su13116419

Agronomy and Ecophysiology of Hemp Cultivation Henri Blandinières and Stefano Amaducci

Abstract Hemp is a crop that in recent years has received renewed attention and been cultivated in numerous countries after having been abandoned by many during the twentieth century. This ‘rebirth’ is due to numerous factors: its favorable agronomical characteristics, its image of being a sustainable crop, and the plasticity of the products it can provide. However, due to its absence for a long time, there is a lack of expert knowledge on cultivating hemp. There is a lack of scientific knowledge regarding the specificities of its biology, and the strong interaction between genotype and environment remains a limiting factor of hemp cultivation, affecting both the yield and quality of the biomass produced. In this chapter, we have discussed the ins and outs of the cultivation of hemp through a scientific prism to address the principal factors, environmental and genotypic, that drive the agronomical characteristics of a hemp crop. Thereafter, we have focussed on the best crop management practices for optimizing hemp cultivation in terms of yield and quality parameters of the different fractions of the biomass that hemp can provide. Keywords Agronomy · Crop management · Cultivation · Ecophysiology · Industrial hemp

Abbreviations BVP CBD FDP GDD LAD LAI

Basic vegetative phase Cannabidiol Flower development phase Growing degree day Leaf angle distribution Leaf area index

H. Blandinières · S. Amaducci (*) Università Cattolica del Sacro Cuore di Piacenza, Piacenza, Italy e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 D. C. Agrawal et al. (eds.), Cannabis/Hemp for Sustainable Agriculture and Materials, https://doi.org/10.1007/978-981-16-8778-5_4

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Maximum optimum photoperiod Nitrogen use efficiency (kg of biomass produced per kg of nitrogen supplied) Nitrogen utilisation efficiency (kg of biomass produced per kg of nitrogen uptaken) Photoperiod inducing phase Photosynthetic nitrogen use efficiency (molCO2 d 1 gN 1) Photosynthetic water use efficiency at canopy level (mmolCO2 molH2O 1) Radiation use efficiency (gbiomass MJPAR 1) Specific leaf nitrogen (gN mleaf 2)

1 Introduction The wide array of potential applications of hemp, arising from the plasticity of its raw products, is one of the main drivers of its recent rebirth, as testified by the increase in acreage observed, for example, in Europe, where it passed from 9400 ha to 34,970 ha from 1994 to 2019 (Eurostat 2021), or in Canada, where hemp cultivation peaked in 2017 with over 60,000 ha (Aubin et al. 2015; Cherney and Small 2016; Moran 2015). The resurgence of this crop also finds its source in several agronomic characteristics, such as its capacity to efficiently insert itself in a rotation system (Gorchs et al. 2017; van der Werf 2002), its ability to suppress weeds (Hall et al. 2014a; van der Werf et al. 1995a; van der Werf et al. 1995b), its ability to structure and enrich the soil (Amaducci et al. 2008a; Robson et al. 2002; ZegadaLizarazu and Monti 2011), its relatively low input requirements in terms of nitrogen and phytosanitary products (van der Werf 2004) and the biomass yields it can achieve, with more than 20 t ha 1 of dry stem reported in a Lithuanian environment (Tang et al. 2016). In addition to the plasticity of its raw products and its agronomic potential, hemp is also adapted to various environments, rendering its cultivation possible throughout an extensive range of latitudes and climates. Such plasticity in the production of raw materials and its adaptability to cultivation under diverse environments, coupled to its favorable agronomic characteristics, has conferred on hemp a renewed interest from the public, producers, industries, and policy makers. However, robust development of the hemp sector can only be achieved through an increase in the scientific knowledge related to its specific biology. This knowledge would bridge the gap that currently impedes an integrated and robust development of this crop. The need to optimize the mechanization of the harvest and post-harvest processes and the limited number of outlets of industrial-scale appear to be some of the main constraints. Also, additional factors that contribute to the difficulty of cultivating hemp include the limited availability of genotypes adapted to specific raw material productions under specific environments, the quality of the raw material produced, and a lack of understanding of the interaction between genotype and environment. The apparent lack of technical knowledge of the producers and

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technical advisors on the specificities of this crop was described as one of the main reasons for the low profitability of hemp in France (Meynard et al. 2013). It is possible to note the absence or scarcity of harvesting systems that harvest aligned long fibres suited for textile end uses that would provide high added value to the biomass produced. The potential that hemp has as an industrial crop has made it the target of the R&D sector, in a drive to bridge the knowledge gaps mentioned previously. Research projects founded in the last decades, such as HEMP SYS, Multihemp, SSUCHY, and GRACE, aimed at achieving a rapid and targeted increase of the scientific knowledge on the biological specificities of hemp and the qualitative and quantitative responses of this crop to environmental factors and crop management. This is of prime importance in the scientific understanding of this crop because of the strong interactions between genotype, environment, and crop management that can affect the hemp’s productivity and quality parameters. Therefore, a successful establishment of the hemp economy can only be achieved through an integrated development approach supported by the latest scientific knowledge of hemp biology. This chapter, therefore, aims to describe the precise understanding of the biology of hemp and how its ecophysiological characteristics should be taken into account for optimizing hemp cultivation by adapting the crop management to the genotype Χ environment interactions.

2 Ecophysiology of Hemp As already discussed, the biology of hemp is heavily influenced by environmental factors. Understanding the effects of environmental parameters on the biology of hemp is a prerequisite for undertaking further technical choices. The study of hemp ecophysiology, i.e., the physiological responses of an organism to the variations of environmental parameters (such as photoperiodism or resources availability), is essential for achieving a better understanding of the biological processes that drive the productivity and the quality of the biomass produced under given environmental conditions. In the case of hemp, the flowering response to photoperiodism is of great agronomic relevance. Suppose the genotypic variability of the flowering induction is one of the main drivers of the adaptability of hemp to a wide range of environments (latitudes), a wrong estimation of the genotype to grow under a given environment can lead to a total failure of the hemp cultivation due to flowering being induced either too soon or too late after emergence. Precocity of flowering in hemp is indeed important because it is one of the main axes of the development of hemp breeders (Salentijn et al. 2015; Thouminot 2015), though the study and scientific understanding of hemp responses to other environmental parameters also have their importance. The response of a crop to resources availability (light, water, nutrients) also strongly influences its agronomical and ecological properties.

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Flowering and Photoperiodism

The success of hemp cultivation is tightly bound up to an appropriate variety choice, and this is particularly true when considering the variability of flowering precocity among hemp genotypes. This aspect in hemp is important and has been one of the most studied traits in this species. Diverse models and experimental investigations aimed at determining the factors controlling the flowering in hemp have been carried out (Amaducci et al. 2008b; Amaducci et al. 2008c; Amaducci et al. 2012; Cosentino et al. 2012; Hall et al. 2012; Hall et al. 2013; Hall et al. 2014b; Lisson et al. 2000a; Lisson et al. 2000b; Salentijn et al. 2019; van der Werf et al. 1994a). Being a shortday plant, hemp flowering is induced at short photoperiods. The environmental characteristics of the place of cultivation (temperature, light quality, and stress factors, but especially the latitude), the sowing date, and the precocity to the flowering of the genotype cultivated strongly influence the duration of the vegetative phase. Usually measured as an accumulation of thermal time, the vegetative phase is a driver of biomass production as stem elongation ceases at flowering (de Meijer and Keizer 1994; Legros et al. 2013; Sankari and Mela 1998). Flowering also coincides with the initiation of senescence, during which assimilates are reallocated from vegetative organs toward reproductive ones. Consequently, the flowering leads to a drop in the photosynthetic efficiency (as discussed in Sect. 2.2) of carbon assimilation and biomass production. The precocity to flowering is a trait under strong genetic control in hemp (Amaducci et al. 2008b; Salentijn et al. 2015). In a given environment, different hemp genotypes display wide variability in flowering time. Hemp flowering has been successively modeled by Lisson et al. (2000a, 2000b) and Amaducci et al. (2008b). Both groups described the post-emergent phenology of hemp as a succession of 3 phases: (i) a juvenile phase (Basic Vegetative Phase – BVP) during which flowering does not occur even under low photoperiod conditions, (ii) a Photoperiod-Induced Phase (PIP) during which the duration of the daylength may induce flowering if the daylength decreases under a critical photoperiod: the maximum optimum photoperiod (MOP) and (iii) a Flower-Development Phase (FDP) occurring between flowering initiation and the appearance of the first flower. The MOP plays an essential role in hemp flowering as the day length under this threshold induces flowering during the PIP, and this threshold is reached on different dates at different latitudes. This also implies that hemp cultivation at latitudes under which the day lengths never exceed the MOP restricts hemp yields as flowering is induced right after the end of the juvenile phase. As an example of this, an experiment in a subtropical environment in Australia showed that hemp cultivation was possible. However, the low maximum day length at those latitudes induced an early flowering that occurred before the summer solstice, reducing the vegetative growth to its minimum (Hall et al. 2014b). The variability of precocity to flowering among hemp genotypes does not, however, seem to be due to variability of the MOP as a relatively constant value of about 14 h was reported among hemp genotypes displaying diverse levels of precocity to flowering (Amaducci et al. 2008b; Lisson et al. 2000b). Despite this, the genotypes used in these models were

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Fig. 1 Representation of the photoperiodic factor of two contrasting cultivars, a low-sensitive one (Futura 77) and a high-sensitive one (Tiborszallasi). Higher values of this photoperiodic factor lead to faster development of the PIP. Here, low-sensitive genotypes display an increase in the development of the PIP at a higher day length than the highsensitive genotypes. The values of the genotypespecific parameters allowing for the calculation of the photoperiodic factor were taken from Amaducci et al. (2008b)

of a limited number and not necessarily exemplary of the genetic variability of hemp. In fact, hemp flowering has been reported at daylengths longer than 14 h (Pahkala et al. 2008) for early flowering cultivars (Fédora 17 and Férimon 12), which flowered respectively on the 6 and 14 of August at 60 of northern latitude, when daylength was still superior to 15 h. The study carried out by Lisson et al. (2000b) and Amaducci et al. (2008b) showed that the variability of precocity to flowering among hemp genotypes could partially be explained by the variability in the duration of the BVP phase, during which low photoperiods could not induce hemp flowering. Being under strong genetic control, the duration of the BVP is, therefore, one of the main drivers of the differences of precocity to flowering among hemp genotypes. Another driver of the variability in flowering precocity among hemp genotypes is sensitivity to photoperiod. A photoperiodic factor for quantifying this genotypespecific sensitivity was studied by Amaducci et al. (2008b). The value of this photoperiodic factor affects the developmental rate of a hemp population during the PIP (photo-induced phase) and depends on the day length. Considering this factor, the developmental rate of the PIP can increase at higher daylength than the MOP, especially for low-sensitive cultivars, as shown in Fig. 1. Modeling hemp flowering is a considerable aid in determining the optimal sowing date for a given cultivar under a given environment that results in the highest yields and prevents heterogeneity of flowering. Amaducci et al. (2008c) has reported differences of up to 99 days in flowering among individuals of a single variety. Such heterogeneity is undesirable in hemp, as it can strongly and negatively affect the crop’s uniformity at harvest, leading to lower homogeneity and quality of the biomass (Legros et al. 2013). The heterogeneity of flowering is relevant in dioecious hemp varieties, with male and female individuals. Being a protandrous species, the male plants flower sooner

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than the females (Amaducci et al. 2008c). Also, male plants are usually taller than female plants, adding further heterogeneity to the crop (de Meijer and Keizer 1994). In an already heterogeneous crop as hemp is (Amaducci et al. 2008c; Sankari and Mela 1998), a variability in flowering among individual plants can lead to dramatic increases in heterogeneity when considering the quality of the biomass, the maturity of the seed, and inflorescences, or the biometric traits. Ultimately, heterogeneity in development makes harvest and post-harvest processes more difficult (Amaducci 2003; Amaducci et al. 2008c; Ranalli and Venturi 2004) and can lead to additional yield losses through an increase in seed shattering (Schluttenhofer and Yuan 2017) or through an inefficient separation of the different fractions of the biomass in the frame of a dual or tri-purpose production (Chen and Liu 2003). Thus, the success of hemp cultivation ultimately depends on understanding the genetic controls determining the duration of the BVP and sensitivity to day length. Sowing an inappropriate cultivar too early could induce early flowering, especially at low latitudes. This would reduce the length of the vegetative growth phase and the amount of biomass produced. This topic in more detail is presented in Sect. 3.4.1.

2.2

Light Use Efficiency

The light use efficiency of a crop describes its efficiency in converting radiation into biomass. It can be measured using different time and biological scales, from the instantaneous light use efficiency at leaf level to the time-integrated measure of the light use efficiency at crop scale over the whole growing season. Each scaling-up of such measurements brings new parameters to be taken into account. The factors driving light use efficiency are light and atmospheric CO2, nitrogen and chlorophyll content, and the sanitary state and age of the leaf studied at the leaf level. By scaling up to canopy level, the variability in the leaves’ age, the architecture, and the leaves’ distribution modify the pattern of light interception. Scaling up even further to crop level extends the measurements over the growing season, implying that the evolution of the light use efficiency during crop growth needs to be taken into account due to changes in its value over time. At this scale, the term radiation use efficiency (RUE) is generally used, and the light use efficiency at the leaf level, usually measured in molCO2 molphoton 1, is measured in gbiomass MJintercepted PAR 1. In hemp, at crop scale, there are two main periods of radiation use efficiency: a high RUE is usually depicted from emergence to flowering and ulteriorly decreases during flowering. This phase marks the onset of the senescence, which induces a reduction of the RUE. Reductions in RUE at the beginning of flowering have been reported several times in scientific literature. In a Mediterranean environment, the RUE of hemp was 2.21 g MJPAR 1 during the whole growing season and under a non-limiting water supply (Cosentino et al. 2013). Also, the same authors observed that if RUE was stable during the phase of vegetative growth, it displayed a reduction at the start of flowering. These observations were corroborated by Meijer et al. (1995). They found similar behavior in the evolution of the RUE in hemp

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during the season’s advancement, with RUE ranging between 1.98 and 2.30 g MJPAR 1 during vegetative growth and decreasing to 0.6–1.2 g MJPAR 1 after flowering. Decreases in RUE after flowering were also observed by van der Werf et al. (1994a). Such a decrease in RUE during flowering can be due to the various changes of metabolism occurring during this developmental phase, with the initiation of senescence, during which assimilates and nutrients are reallocated from the vegetative organs (leaves essentially) toward the reproductive ones (inflorescences), hence leading to a loss of photosynthetic efficiency. Seed synthesis can equally explain the decrease in RUE because of the high levels of metabolic energy required to synthesize the large fractions of fats and proteins of the seeds, as described for colza (Rode et al. 1983). Similarly, the lignification and the secondary growth of the stems required for a plant to withstand the weight of the inflorescences (Westerhuis et al. 2019) also mobilizes a relatively high fraction of the metabolic energy (greater than cellulose synthesis, Meijer et al. 1995). This further impacts the global RUE of the crop. Cosentino et al. (2013) also reported that the RUE was negatively impacted by reductions of water availability, decreasing from 2.21 g MJPAR 1 under non-limiting water conditions to 1.88 g MJPAR 1 under water stress treatments. This introduces the importance of water availability for a hemp crop cultivated under a semi-arid climate and is discussed in Sect. 3.6. When compared to other crops, the values of RUE reported for hemp (Cosentino et al. 2013; Meijer et al. 1995; van der Werf et al. 1994a) are similar or higher than those reported for other non-leguminous C3 crops (Gosse et al. 1986), higher than those for leguminous C3 crops, but lower than those reported for C4 crops. From the date of emergence, canopy closure in hemp is relatively fast, taking about 400–500 growing degree days (GDD) (Amaducci et al. 2002a; Meijer et al. 1995; van der Werf et al. 1995c), which is partially due to its planophile leaf angle distribution (LAD, Fig. 2). This induces a higher RUE during the first stages of crop development by comparison to other non-leguminous C3 crops. However, this may be balanced by other factors. The self-thinning of hemp observed at high plant densities leads to biomass losses, and hemp’s high light extinction coefficient (close to 1, Meijer et al. 1995; Tang et al. 2018) would induce a reduction of RUE. By using the crop growth model SUCROS, Meijer et al. (1995) indeed showed that artificially decreasing the light extinction coefficient of hemp from 0.96 to 0.75 led to a 2.6 to 2.9% increase in RUE, depending on the plant density. These authors also hypothesized that a low canopy photosynthesis rate or a high respiration rate could also explain the low RUE of hemp but found values of canopy photosynthesis similar to those of other C3 crops. It appears that hemp photosynthesis seems to be relatively efficient. Two studies by Tang et al. (2017b, 2018) aimed at modeling the photosynthesis of hemp, based on the model of Farquhar et al. (1980), showed that hemp displayed a high photosynthetic capacity when compared to other fibre crops such as kenaf or cotton.

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Fig. 2 Picture of a hemp canopy taken 31 days after emergence in Piacenza (Italy), showing that the planophile LAD of hemp leads to fast canopy closure, a rapid increase in RUE at the beginning of the growing season, and suppression of weed growth

3 Hemp Cultivation Management Until now, it has been made clear that understanding hemp biology is a prerequisite for the successful cultivation of hemp. It will now be explained how the ecophysiological characteristics of hemp interact with environmental and contextual variables and how, by considering these interactions, the producers can make decisions on the technical choices for achieving successful hemp cultivation.

3.1

Choices of Raw Material Production and Variety

Choosing the variety and the raw material to be produced are the first decisions a grower must take when cultivating industrial hemp. These two choices are intrinsically bound and depend on the contextual parameters. Also, these choices are the first that can determine the success or otherwise of the cultivation. Hemp aboveground biomass is made up of different fractions that can all be processed for obtaining various end-use products of variable added-value, depending on the quality of the harvested material. The stem contains bast fibre and shives, while the inflorescences contain seeds and flowers (on female plants or in monoecious varieties): The flowers are of interest in the context of CBD and essential oil production. Hemp harvest can be realized in two main ways. The first is a combined

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harvest in which hemp is cut both at ground level and under the inflorescences, separating them from the stems. Alternatively, it can be realized as simple reaping, with stems cut at ground level, stems and inflorescences remaining unseparated. In the case of a combined harvest, aboveground hemp biomass is separated into two main fractions: bast fibres and the shives can be obtained from the stems. At the same time, the inflorescences are usually processed within a combined harvester to separate the seeds from the flowers, the latter being called threshing residues. Choosing which fraction to harvest is not as straightforward as it may seem. Favoring the optimal harvest of one fraction can have deleterious effects on the yield and quality parameters of the other, ultimately leading to a depletion of the potential added value of the raw material. For example, the dual-purpose production of seeds and stems requires the hemp crop to be harvested when it reaches the stage of seed maturity. However, harvesting at this developmental stage can have deleterious effects on the quality of the bast fibre, as lignification and secondary growth occur in the stem, presumably to enable the plant to support the weight of the inflorescences (Westerhuis et al. 2019). These processes ultimately lead to decreased fibre quality than the fibre obtained by harvesting at full-flowering (Liu et al. 2015a; Mediavilla et al. 2001; Westerhuis et al. 2019). Inferior fibre quality renders it unsuitable for high added value end-use applications such as textiles or bio-composites. The raw material production must equally be chosen depending on several other features: (i) the storage and transformation facilities available in the proximity of the place of production, (ii) on the existence of a market of relevant scale, (iii) mechanization available for harvesting the crop and (iv) the legal specifications of the country of production, for example in France the harvest of inflorescences is forbidden. The storage of harvested raw material may not pose any difficulties for stems, but inflorescences harvested for seeds and CBD production require immediate drying under specific conditions to prevent the development of fungi or the degradation of the biochemical compounds. In particular, for the seeds, drying is often advised to be undertaken within the 4 h following the harvest and must be carried out at temperatures lower than 40  C. The flowers or threshing residues, which can be used for cannabinoid extraction, must also be dried as soon as possible after harvest at temperatures below 70  C (Fournier et al. 2011). Stems may be retted to facilitate the post-harvest processing of the hemp stems. Retting ultimately increases the decortication efficiency, reduces the energy consumption during the process (Booth et al. 2004), and enables finer fibres to be obtained (Musio et al. 2018). The retting is traditionally realized by two methods: a water retting in a water basin or an in-field retting where cycles of humidity and drying of the biomass, caused by the morning dew and the rainfalls, allow the development of micro-organisms that degrade the pectins that bind the fibre cells together. The first retting method requires that water basins are available within proximity of the field. In contrast, the second implies that the field must remain available for the duration of the dew-retting. The choice of the raw material(s) to harvest must equally be made following the presence or absence of local primary transformation facilities to avoid expensive shipping costs of tons of raw material to facilities situated far away from the

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cultivation site, a point highlighted by Meynard et al. (2013) as being the main reason for regionalizing hemp production in France. Last but not least, the choice of the raw material to produce must also be driven by the environment of cultivation as different environmental conditions, especially when considering the latitude of the cultivation, may limit the plasticity of choices of raw materials to harvest. More precisely, cultivating hemp at high latitudes would lead to late flowering as day lengths are longer at higher latitudes during the hemp cultivation period. Seed maturity can occur relatively late in the season. Sometimes, when climatic conditions are unfavorable for harvesting, this situation is particularly true for late flowering cultivars. As an example, in a recent study performed with 14 hemp cultivars in 4 contrasting environments in Europe, Tang et al. (2016) reported that the seed yield in Latvia could only be established for the two earliest flowering cultivars as killing frost occurred before seed maturity was reached for the other 12 cultivars. de Meijer and Keizer (1994) experienced a similar phenomenon in the Netherlands when studying a wide number of hemp accessions; the two latest flowering cultivars did not produce seeds because of frost. Tang et al. (2016) revealed, however, that the stem yields achieved in Latvia were consistently higher than those attained in the other 3 locations (Italy, France, and the Czech Republic), and this was especially true when considering the late-flowering cultivars with achieved stem yields of up to 22.7 Mg ha 1 for Carmagnola Selezionata (an Italian originating cultivar). Because of the long day length at these high latitudes, the vegetative growth phase lasts for a long period, leading to higher amounts of thermal time before the initiation of the flowering. However, this does not imply that hemp seed production should be abandoned at high latitudes as hemp varieties have been specifically bred for seed production at high latitudes (Callaway 2004). The cultivar Finola reaches an average seed yield of up to 1.7 Mg ha 1 in Eastern Finland and is successfully cultivated in several high latitude countries for seed production only (Vera et al. 2004; Vera et al. 2010). There is, however, a counterpart for these high seed yields under such environments: the aboveground biomass production is generally low, which results in poor fibre yields, limiting the potential of cultivating hemp as a dual or tri-purpose crop. On the other hand, harvesting a hemp crop for seed is more easily realized on short-sized plants. Cultivating hemp varieties at lower latitudes than that for which they were bred, however, has no up-side. Early flowering varieties (e.g., Finola or Earlina 8), if grown at low latitudes, produce insufficient material for a decent harvest of any type. Locally bred cultivars or cultivars bred at slightly higher latitudes, displaying medium to late precocity to flowering, should be used for fibre, seed, dual or tri-purpose productions. It is easy to understand, from these elements, that the environment and the choices of cultivar and of which raw material to produce are intrinsically bound up and represent strong determiners in successful hemp cultivation. Other parameters such as the industrial context and the existence of a market of relevant scale must also be considered for determining the choices of material to harvest and the cultivar to grow. In addition to all this, the sexual characteristic of hemp should also be considered when choosing the variety. Breeders have modified the natural dioecious state of

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hemp to obtain monoecious cultivars (Salentijn et al. 2015; Thouminot 2015). These two types of sexuality coexist today and display different characteristics in terms of raw material quality. Dioecious cultivars are better suited for sole fibre production as they tend to be more productive than monoecious ones when considering stem biomass (Cosentino et al. 2013; Sankari 2000; Tang et al. 2016), probably due to the tendency of the dioecious cultivars to flower later than monoecious ones (Bertoli et al. 2010; Cosentino et al. 2012). Instead, they are less suited for seed, dual, or tri-purpose productions as the fraction of male plants in these populations do not produce seeds or inflorescences containing cannabinoids. Therefore, the cultivation of dioecious lateflowering cultivars represents a good choice in many environments if the only production aim is fibre production. These varieties reach their highest stem yields in high latitude environments (Tang et al. 2016). They can also be sown relatively early at low latitudes, achieving an extended vegetative growth period and a high biomass yield. Monoecious cultivars, on the other hand, are suited to dual or tri-purpose productions in diverse environments. However, this suitability is somewhat limited at low latitudes compared to late dioecious cultivars because of their earlier flowering, ultimately leading to lower stem production. Despite this, monoecious cultivars with slightly delayed flowering are available in the market and enable consistent biomass yields to be obtained at Mediterranean latitudes (Cosentino et al. 2013). The lack of monoecious cultivars displaying late-flowering phenotypes similar to those of dioecious cultivars bred for low latitudes, such as Fibranova, Carmagnola Selezionata, or Eletta Campana, that would otherwise enable higher yields of the various fractions of the biomass in dual or tri-purpose productions, represents today one of the main bottlenecks in the development of the hemp sector in these environments. The limited biomass productivity of these monoecious cultivars puts constraints on hemp cultivation for dual or tri-purpose productions. It, therefore, limits the development of local channels, from production to market. The variety choice can become even more complicated when considering the specificities of the genotypes regarding the quality of the biomass they produce. One of the main traits of importance in fibre production lies in the bast fibre content and its quality (Amaducci et al. 2008d; Salentijn et al. 2015; Westerhuis et al. 2019). Strong interactions exist between these quality parameters, the environment, and the crop management practices, though these quality parameters are also strongly determined by the genotype (Amaducci et al. 2008e; Campiglia et al. 2017; Cromack 1998; de Meijer and Keizer 1996; Fernandez-Tendero et al. 2017; Jankauskiene et al. 2015; Legros et al. 2013; Mankowska and Silska 2015; Musio et al. 2018; Müssig and Amaducci 2018; Petit et al. 2019; Sankari 2000; Struik et al. 2000; van der Werf et al. 1994b; Westerhuis et al. 2009a). Until recently, the genotype dependence of quality parameters was one of the leading development axes of the French breeders Hemp-it (Thouminot 2015), though the focus is now on developing cultivars that achieve a higher stem production via delayed flowering while maintaining the levels of bast fibre content that were already achieved in the previously developed cultivars. Hemp-it also recently started to focus on the easiness of fibre decortication – in response to the emergence of a market for technical fibres, as transformers seek a raw material that is easy to

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Fig. 3 Aerial view of a trial involving a common “green” variety (Futura 75) and a “yellow” variety (Fibror 79) at seed maturity in northern Italy

decorticate. The existence of a particular phenotype displaying yellow stems, leaves, and inflorescences (Fig. 3), (originating to our knowledge from a work of Hoffman 1947, cited by Grassi and McPartland (2017) and having been further adapted to other monoecious cultivars (Chamaeleon, Markant, Ivory, Marcello, Carmaleonte, Fibror 79), has potential for achieving high levels of decorticability. These genotypes indeed seem to present interesting properties of high bast fibre content coupled to the easiness of fibre decorticability, leading to efficient separation of the bast fibres from the shives (Musio et al. 2018). Today, the bast fibre content of hemp ranges from 30 to 50%, depending on the cultivar (Legros et al. 2013; Mankowska and Silska 2015), but the increase of bast fibre content dictated by breeding programs may have led to a concomitant decrease of the overall quality of the fibre with increases in the ratio of secondary to primary fibres (Amaducci et al. 2020). The secondary fibres are usually shorter and, therefore, of lesser quality and cannot be processed in textile lines (Westerhuis et al. 2019), decreasing the potential of using the bast fibre for high added-value applications such as textiles (Liberalato 2003) or biocomposite materials (Duval et al. 2011; Liu et al. 2017). The secondary to primary fibre ratio also depends on the stem fraction from which the sample is taken. Apical parts are usually richer in primary fibre, while the basal parts of the stems, which have more secondary growth, have higher levels of secondary fibre (Amaducci et al. 2008e; Liu et al. 2015b; Westerhuis et al. 2019). Suppose hemp breeding has focused in the last years on increasing the bast fibre content. In that

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case, there is not, to our knowledge, any breeding programme that aimed at developing varieties displaying improved fibre quality parameters such as fibre fineness, Young’s modulus, the ratio of secondary to primary fibres, or the mechanical resistance to traction, all of which could increase the potential for producing high added-value end products. As already stated, one of the major reasons for the recent rebirth of hemp lies in its ability to provide an array of raw materials of potentially high added value. In the case of a dual-purpose crop, the recovery of the threshing residues could increase farmers’ income to produce stems and seeds. These threshing residues can contain a relatively high content of cannabinoids, among which CBD interests pharmaceutical companies (Calzolari et al. 2017). They can also be used for extracting essential oils that are, as the cannabinoids, specific to the cannabis genus, even though the market of essential oils is still a niche market (Bertoli et al. 2010). However, through the medical applications, it can provide, CBD represents a market of way larger scale, currently in a positive dynamic (Wheeler et al. 2020). In some places, it has led to hemp being cultivated exclusively for CBD production. As an alternative to a tri-purpose production of (stems, seeds, and threshing residues), hemp can be harvested at full-flowering to produce high-quality fibre and an inflorescence with high cannabinoid content. Despite the growing interest in CBD production, scientific literature on the subject remains scarce today, especially considering the effects of the environment X genotype X crop management interactions on the CBD production in industrial hemp. It appears, however, that the content of CBD in the inflorescences is under strong genetic control (Calzolari et al. 2017; Campbell et al. 2019; Fournier et al. 2004), and if a CBD production is intended, cultivars with high CBD content should be selected. In this regard, dioecious cultivars appear to display higher contents of CBD than monoecious ones (Calzolari et al. 2017), while monoecious produce larger inflorescences (Bertoli et al. 2010).

3.2

Hemp in a Crop Rotation

The possibility of efficiently inserting hemp into a crop rotation is another reason for its recent resurgence. Hemp is an annual plant that, due to its short-day requirements for flowering, must be grown around the summer solstice and is therefore usually sown early-mid spring and harvested at the end of the summer. Desanlis et al. (2013) reported that rotation hemp is usually grown before winter wheat cultivation. Meynard et al. (2013) stated that hemp displayed an interesting “preceding effect” that seduced the producers, even though there is a lack of quantitative/scientific data supporting these statements. Van der Werf (2002) reported that hemp is much appreciated in crop rotations, especially before a winter wheat cultivation, because of its ability to suppress weeds and its soil structuring properties. In a recent study realized in northern Spain, Gorchs et al. (2017), through diverse combinations of fertilizer and rotations of hemp and wheat, showed that a winter wheat crop that followed hemp increased grain yield by 47% and 6% in the first and second year

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after the hemp cultivation, respectively, when compared to a succession of wheat cultivation. The beneficial effects of hemp ultimately disappeared after three years. Positive effects of hemp cultivation on the yields of a successive crop of winter wheat have been reported to be similar to those of leguminous crops (alfalfa and pea). These positive effects were greater than those of other main crops: barley, wheat, maize, rapeseed, sunflower, and sugar beet (Allard et al. 2017). Such statements are in accordance with Ranalli (2004), who reported that hemp could have positive effects on the crop following it in the rotation. The positive effects of hemp on the successive crop are due to several reasons. Desanlis et al. (2013) pointed out its weed suppressing capacity as one of the main factors responsible for the beneficial effects of hemp. Hemp’s fast canopy closure and increase in height in the first phases of its growth suppress weed growth and break the reproductive cycle, meaning that in autumn, the successive crop will be less prone to face strong weed competition for resources. However, this weed suppressing capacity depends on the density at which hemp is sown; higher sowing densities lead to faster canopy closure and higher height increments in the first phase of hemp growth due to the shade avoidance syndrome (Hall et al. 2014a). It is also thought that hemp acts as a weed suppressor through the release of allelopathic substances. Singh and Thapar (2003) reported strong inhibitive effects of aqueous extracts of female hemp leaves on the germination of seeds of Parthenium hysterophorus. However, to our knowledge, no field-scale experiments have been carried out for quantifying or validating this hypothesis. In addition to the weed-suppressing capacity of hemp, Desanlis et al. (2013) reported that sugar beet producers found that hemp reduces the populations of nematode (Heterodera schachtii) that affect this crop. Additional features of hemp that make it an interesting crop in a rotation include its tendency to resist pests. Being able to cultivate hemp without the need for pesticides could favor local biodiversity. At the same time, its taproot, which was found up to 2 M deep in the soil (Amaducci et al. 2008a), is an interesting trait for cultivation in a semi-arid environment, especially considering that it may also facilitate the root growth of the successive crop in the rotation enabling them to reach deeper soil layers. As for any other crops, mono successions of hemp are not recommended. In a 12-year trial of hemp monoculture carried out in France, Desanlis et al. (2013) reported that hemp yields declined progressively, in particular, because of the strong development of the hemp broomrape, a known parasitic plant of hemp that caused increased rates of plant death in the successive hemp crops.

3.3

Soil Preparation

Soil preparation is an important step for achieving a fast and homogeneous emergence and reducing the risk of hemp roots being stopped by soil compaction layers. The usual soil preparation consists of a fall or winter ploughing of 30–40 cm depth,

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while the seedbed preparation should be performed right before the sowing (Amaducci et al. 2015). The ploughing is especially important for soils of fine texture that can easily develop compaction layers, which may hinder the growth of hemp’s taproot, causing it to take an L-shape (Adesina et al. 2020; Amaducci et al. 2015; Desanlis et al. 2013). Such non-vertical development of the taproot ultimately affects hemp’s ability to uptake the water and nutrients stored in deep soil layers, which may increase the risk of water stress. It can also increase the risks of logging, especially when the crop is tall and starts developing inflorescences, or if the soil becomes too wet after heavy rainfall and or there are strong winds. Even though no scientific data on the effect of soil compaction on hemp seed germination is available, the effects of superficial compaction layers have been reported to strongly alter the homogeneity of the emergence and development of the crop (Sankari and Mela 1998). This underlines the importance of a well-prepared seedbed to allowing sowing at a constant depth, thus favoring a homogeneous emergence and early development of the crop. Compaction layers in clay soils may lead to additional adverse conditions as their low porosity can reduce the water drainage, creating hypoxic conditions. In such conditions, hemp growth is stunted and may be halted, sometimes irreversibly. Clay soils, therefore, require deep soil work. Fine texture soils, on the other hand, are susceptible to forming a slacking crust. This is to be avoided as it strongly impairs the crop’s emergence.

3.4

Sowing

The diverse sowing parameters (date, depth, and density), as for all crops, must be chosen with great attention. Emergence is generally a phase during which a crop is highly susceptible to stress factors. The quality of the crop establishment, its homogeneity, and ultimately the yield in terms of quantity and quality depend on the sowing quality.

3.4.1

Sowing Date

The sowing date is a critical parameter that must be chosen according to the soil and air temperatures. Once established, hemp can resist light frosts of 5  C up to the fifth pair of leaves (Desanlis et al. 2013). The germination and emergence are mainly driven by thermal time accumulation. In their work modeling the pre-emergence of hemp, Lisson et al. (2000c) only considered temperature as the driver of this process. Their model does not consider any stress factors such as water, heavy metals, or compaction stresses and, therefore, describes hemp’s pre-emergence process under optimal conditions, depending solely on temperature. The model predicted germination at 86.1 GDD of thermal time accumulation over a base temperature of 1  C for a sowing depth of 30 mm; two greenhouse experiments showed germination at a thermal time accumulation of 81.2 and 91.3 GDD. These values are as per data found

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in the literature. Legros et al. (2013) reported 85 GDD between sowing and emergence, with a potential delay in case of abundant rainfalls; Lisson et al. (2000c) reported 96 GDD with a base temperature of 0  C; and van der Werf et al. (1995c) reported 68–109.5 GDD. The base temperature for germination, radicle, and hypocotyl growth, depending on the authors, are 0–1  C. Still, given the strong effect of temperature on these processes, a soil temperature of at least 8–10  C is usually advised for guaranteeing fast and homogeneous germination and emergence (Amaducci 2020; Desanlis et al. 2013), which allows for a fast and homogeneous canopy closure and this, in turn, increases the pressure on weeds and reduces the crop’s heterogeneity during growth and at harvest. As critical parameters for the germination and emergence of hemp, air and soil temperature must be considered alongside latitude, cultivar, and targeted raw materials when deciding a sowing date. As already discussed in Sect. 2.1., early sowing can lead to early flowering if the crop enters the Photoperiod Inducing Phase (PIP), while daylength is still shorter than the critical day length of about 14 h, potentially ending up in dramatic yield losses and/or in a strong heterogeneity of development among individual plants. Therefore, the sowing date must be carefully chosen for achieving a correspondence between the moment at which the critical day length occurs (specific of the latitude of cultivation) and the moment at which PIP begins. This last being driven both by the genotype (the duration of the Basic Vegetative Phase being a genotype dependant parameter) and the thermal time accumulation. Achieving an optimal sowing date ultimately allows for extending the vegetative growth and, therefore, the yield of the biomass produced. Therefore, the producer’s decision on the sowing date becomes a critical factor for achieving high yields. A poorly chosen sowing date can have significant adverse effects on the biomass yield and its quality parameters. Still, it is easily understandable from the post-emergent phenological model of Amaducci et al. (2008b) that the optimal sowing date is heavily dependent on the interactions between genotype and environment (especially temperature and photoperiod), making it highly variable depending on the cultivation conditions. Therefore, defining the best sowing date for a given variety in a specific environment is important. Figure 4 shows how the vegetative phase’s duration is affected by the date of emergence for 3 different cultivars and one cultivar in two locations. The variety and emergence date choices are decisive drivers of the duration of the vegetative phase under given environments. The left panel (a) shows the flowering behavior in northern Italy of three different cultivars: early flowering Félina 34, medium flowering Futura 77, and late-flowering Carmagnola. The emergence of Félina 34 and Futura 77 before beginning to mid-April drastically reduces its vegetative growth phase. Carmagnola, on the other hand, does not pre-flower under conventional sowing times. The right panel (b), instead, shows the simulated duration of the vegetative growth for the cultivar Félina 34 in two different environments - northern Italy 45.0 N and western France 47.4 N, with a mean difference of temperature of 3  C. Here, a slight increase of latitude, coupled with a slight decrease of mean temperature, put the optimal sowing time a bit later, and it lengthened the duration of the vegetative growth. These graphs demonstrate the interaction between

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Fig. 4 Simulated values of the duration of the vegetative phase as a function of the date of emergence. (a) Duration of the vegetative growth as a function of the date of emergence for 3 cultivars in northern Italy (45 N). (b) Duration of the vegetative growth of the variety Félina 32 as a function of the date of emergence for two different environments: northern Italy (Piacenza, 45 N) and western France (Beaufort-en-Anjou, 47.4 N)

environment, genotype, crop management (i.e., sowing time), and the extent to which these factors can affect the duration of the vegetative growth and the yield at harvest. Hemp phenology models that include environmental and genotypic variables have massive potential as decision support tools for determining the optimal sowing dates. However, they are currently limited in terms of the cultivars they can model. Expansion of these models to other and new genotypes should therefore be prioritized. Until now, we have focused on optimizing the sowing date to get the best possible vegetative growth phase; however, this is not always the case. When growing hemp for seed production meridional or semi-arid environments, for instance, the best strategy may be early sowing of an early to medium flowering variety. In adopting such a strategy, the crop may flower relatively early without becoming particularly tall. This could be beneficial at harvest. In addition, having completed its growth cycle reasonably early in the season, it may not suffer drought stress later on. This is of particular importance in seed production as the seed filling process requires a constant and vigorous water flux within the plant for achieving an efficient translocation of nutrients and assimilates, which can only be achieved with good levels of soil water availability. Maintaining such levels of soil water availability under semiarid climates during the seed filling process will most certainly require the use of irrigation (Cosentino et al. 2013) if the sowing is carried out at the traditional dates, as the seed filling process would be postponed until full summer. The adoption of a “premature sowing” strategy using cultivars bred for higher latitudes, on the other hand, makes seed production more sustainable due to its reduction in water requirements. It is similar to the breeding strategies performed on other crops aimed at reaching high levels of water use efficiency by selecting the traits of the intrinsic earliness of phenology for achieving a growth cycle during cooler months of the year

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when the evaporative demand is lesser, therefore decreasing the total water consumption by the crop (Condon et al. 2004; Richards 1991). Such a strategy of early sowing has limited interests or possibilities at higher latitudes; however, as drought is less likely to occur and sowing too early risks frost-killing seeds at the germination stage. Such a strategy is also not viable for the stem, dual, or tri-purpose hemp productions as these all require high aboveground biomass productivity and therefore need to adopt a strategy of extended vegetative growth, as hemp aboveground biomass production is strongly correlated with the duration of the vegetative phase (Legros et al. 2013; Tang et al. 2016). Similar to the strategy of early sowing, growers can also contemplate a strategy of postponed sowing for high-quality fibre production for maximizing land use, sowing hemp after an early crop such as barley or pea. In an experiment carried out in the Netherlands, Westerhuis et al. (2009a) showed that stem yields of about 5 t ha 1 could be obtained on 2 hemp cultivations by sowing the first one at a traditional date (27th of April) and harvesting mid-July and by sowing the second one at the end of July and harvesting it on the first of October. Shortening the duration of the cycle of each of these cultivations reduced stem length (an average of 131 cm and 118 cm for the first and the second crop, respectively), making both crops relatively easy to harvest and, more interestingly, rendering their stem biomass processable in the pre-existing flax scutching and hackling lines, adapted to stems of about 100 cm. This alternative strategy can give respectable yields of high-quality fibre for high added-value textile applications if coupled to high sowing densities.

3.4.2

Sowing Density and Modality

Hemp is usually sown with a standard drilling machine for winter cereals and rows spaced 12–20 cm. The distance between rows was shown to affect the fraction of intercepted light and the leaf area index (LAI) of a crop in the first phases of its growth between row spacings of 12.5, 25, and 50 cm (van der Werf et al. 1995b), even though no significant effect could be observed on the biomass production at the end of the growing season. Maintaining a reduced distance between rows can be advisable for achieving better control of weeds and better resource-use efficiency. However, in some cases, such as hemp cultivation for seed multiplication of monoecious varieties, implying the passage of operators between hemp plants for eliminating the dioecious males, the distance between each plant must be kept relatively high for facilitating the work of the operators. A similar situation can be encountered in CBD production in dioecious varieties. Dioecious males must be eliminated to prevent pollination of the female plants, which would otherwise negatively affect the yield and the quality of the inflorescences (Small and Naraine 2016). Plant density should be lower in both these cases than for hemp fibre cultivations. A larger inter-row distance (70–100 cm) and pneumatic precision sowing machine may be used. A sowing depth of 2–3 cm is advisable to prevent the seeds from drying out before germination. Deeper depths can be avoided to prevent a slow and

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heterogeneous emergence, as occurs when the hypocotyl needs to reach a greater length to emerge (Amaducci et al. 2015; Desanlis et al. 2013). If sowing is realized in a relatively humid environment, the sowing depth can rise to 1–2 cm. Sowing density is a critical parameter and must be chosen based on the targeted production. The scientific literature on the effects of sowing density on yield and quality parameters of hemp is relatively large, underlying the importance of this parameter in the technical choices of hemp cultivation. Several authors report that differences in sowing density do not or barely affect the biomass yield for densities ranging from 30 to 300 plants m 2 at emergence (Amaducci 2020; Amaducci et al. 2002a; Amaducci et al. 2002b; Cromack 1998; Grabowska and Koziara 2006; Lisson and Mendham 2000; Meijer et al. 1995; Struik et al. 2000; van der Werf et al. 1995a; Westerhuis et al. 2009b). However, some authors display contradictory results, such as Burczyk et al. (2009) showed that the maximum biomass yield was obtained at a sowing density of 30 kg ha 1 (corresponding roughly to 130 plant m 2). Decreasing or increasing sowing densities from 30 kg ha 1 led to reductions in biomass yield. Tang et al. (2017a) similarly reported that the biomass yield was positively and significantly affected by increasing plant densities at emergence from 30 to 240 plants m 2. Higher sowing densities are required for fibre production than for seeds and threshing residue production. The optimal sowing densities vary depending on the researched fibre quality and depending on the targeted fiber production. Targeted plant densities at emergence as high as 200–750 plants m 2 (Dempsey 1975) or 300–500 plants m 2 (Hall et al. 2014a) were reported as the optimum plant densities for producing high-quality fibre. Contrary to this, the Italian traditional hemp cultivation for textile fibre production is performed by sowing at relatively lower densities of 90–100 plants m 2 (Venturi and Amaducci 1999). After analyzing large datasets issued from various sources in France, Legros et al. (2013) reported that sowing densities of about 40–50 kg ha 1, corresponding roughly to 150–200 plant m 2 at emergence, usually allow for optimized yields of fibre. They observed that sowing densities lower than these led to proportional decreases of fibre yield and identified two main reasons for this decline: a decrease in stem productivity alongside a decrease of the bast fibre content. On the other hand, increasing densities above 50 kg ha 1 does not lead to increased fibre yields. The high sowing densities applied in productions of high-quality fibre are done in the interest of increasing the quality parameters of the fibre. Sowing density plays a vital role in determining numerous morphological variables of a hemp crop, which ultimately affect the yield and the quality parameters of the stem biomass produced. Increases in stem density from 10 up to 1280 plants m 2 were shown to reduce the crop’s height (Amaducci et al. 2001; Amaducci et al. 2002a; Amaducci et al. 2002b; Campiglia et al. 2017; Grabowska and Koziara 2006; Hall et al. 2014a; Struik et al. 2000; Tang et al. 2017a; Westerhuis et al. 2009b) and stem basal diameter (Amaducci et al. 2001; Amaducci et al. 2002a; Amaducci et al. 2002b; Campiglia et al. 2017; Hall et al. 2014a; Tang et al. 2017a; Struik et al. 2000; Westerhuis et al. 2009b), while increases of plant density from 10 to 270 plants m 2 were reported to lead to increases of the stem’s slenderness (height to weight ratio,

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van der Werf et al. 1995a) and the length of the internodes, especially the basal ones (Amaducci et al. 2002a). These modifications of the biometric parameters of the stems induced by higher sowing densities tend to make mechanized harvest easier (Legros et al. 2013) and have positive effects on several quality traits of the stem biomass produced. Indeed, the decrease of stem diameter observed at high sowing density results from a reduced secondary growth of the stems (Amaducci et al. 2002a), which consequently induces a lower ratio of secondary to primary fibre (Amaducci et al. 2002a; Amaducci et al. 2005; Keller et al. 2001). Amaducci et al. (2005), Amaducci et al. (2008e), Hernandez et al. (2007), Mediavilla et al. (2001), van der Werf et al. (1994b), and Westerhuis et al. (2009b) all described the distribution pattern of these secondary fibres as decreasing from the bottom to the upper parts of the hemp stem. Westerhuis et al. (2019) later strengthened this information, showing that the secondary fibre formation was correlated both with the weight and height of the plant. They hypothesized that this phenomenon is a response of mechanoperception allowing the plant to support its weight and concluded that harvesting relatively short hemp plants of about 1.3–1.4 M height could end up in strong limitations of the ratio of secondary to primary fibre. What is more, high sowing densities are also thought to positively affect the quality of the fibre produced through the effect they have on the crop growth rate. Amaducci et al. (2002a), Amaducci et al. (2005), and Hall et al. (2014a) observed higher crop heights in the first phases of the growing cycle at the higher sowing densities, despite having concurrently observed lower heights at the higher sowing densities at the end of the season. These authors explained this phenomenon as resulting from the shadeavoidance syndrome, an inter-plant competition for the light resource. This increased stem elongation rate ultimately led to longer internodes (Amaducci et al. 2001; Amaducci et al. 2002a; Amaducci et al. 2005) which in turn were shown to increase the length of the primary fibre (Kundu 1942). The effect of crop density on the total bast fibre content in the stem is, however, more ambiguous, as several authors reported a positive correlation between these two parameters from 10 to 400 plants m 2 at emergence (Cromack 1998; Legros et al. 2013; van der Werf et al. 1995a) while other ones found either slight though not significant effects (Hall et al. 2014a; Lisson and Mendham 2000), or no effect at all (Burczyk et al. 2009). Furthermore, the primary fibre fineness, a desirable trait for textile applications, was also shown to be positively impacted by sowing densities increasing from 90 to 360 plants m 2 (Amaducci et al. 2005; Amaducci et al. 2008e; Müssig and Amaducci 2018; Rahman Khan et al. 2011). Another advantage induced by higher sowing densities lies in the faster canopy closure (Amaducci et al. 2002a; Meijer et al. 1995; Tang et al. 2017a), leading to an increased RUE and increased pressure on weeds (Hall et al. 2014a). However, suppose relatively high densities of at least 200 plants m-2 at emergence are recommended for high-quality fibre productions. In that case, it is also necessary to consider that when sown at too high a density, hemp may suffer from selfthinning. This aspect is very well-documented (Amaducci et al. 2002a; Burczyk et al. 2009; Grabowska and Koziara 2006; Lisson and Mendham 2000; Meijer et al. 1995; Struik et al. 2000; van der Werf et al. 1995a) and becomes more severe as the

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sowing density increases, an effect that was highlighted by Meijer et al. (1995). Ultimately, van der Werf et al. (1995a) described the optimum sowing density as that allowing for maximizing the crop yield and quality parameters (high fibre content, low ratio of secondary to primary fibre) without being subject to the deleterious effects of self-thinning, which represents a loss of biomass and therefore reductions in resource use efficiency, as well as a financial loss. In the frame of a dual-purpose production of seeds and stems, the main production typology in Europe, the hemp crop must be harvested at seed maturity. However, harvesting at this developmental stage has led to relatively high contents of short and lignified secondary fibres in the stems (Mediavilla et al. 2001; Westerhuis et al. 2019) that are unsuitable for high added-value applications. According to Westerhuis et al. (2019), hemp cultivation destined for such a dual-purpose production cannot be considered for providing the raw material to the processing lines to produce high added-value products, or rather textiles and yarns. Therefore, a hemp producer should not seek to establish the highest quality fibre but instead focus on achieving high yields of both seeds and stems. Such a production typology is equally valid for a tri-purpose production of seeds, threshing residues, and stems. By considering these facts and the low effect of the sowing density on the total biomass yield as discussed, a producer should contemplate sowing lower densities to decrease the costs of buying the seeds and, secondly, to achieve consistent productivity of inflorescences. Several experiments on the effects of density on seed productivity have been carried out. In general, sowing densities of about 30–40 kg ha 1 (100–150 plants m 2 depending on seeds characteristics) are advised. Campiglia et al. (2017) obtained increasing seed yields with plant densities at emergence from 40 to 120 plants m 2. Legros et al. (2013) reported that sowing densities lower than 20 kg ha 1 are not advisable due to the difficulty of the hemp crop to suppress weeds, therefore leading to a stagnation of the seed yield. These last authors also showed that hemp seed yield remained relatively high up to sowing densities of 30 or even 40 kg ha 1, without observing noteworthy decreases of the so-called hurd yields. However, above 40 kg ha 1, they reported that seed yield started to decrease. Stafecka et al. (2016) showed continuous decreases of seed yields with increasing sowing densities from 50 to 110 kg ha 1. In a recent study performed with several cultivars under different environments in Europe, Tang et al. (2017a) investigated the effects of sowing density and nitrogen fertilizer on diverse parameters of hemp cultivation. They did not observe any effects of sowing density on the seed yield. They concluded that the optimal sowing density for dual-purpose cultivation of stem and seeds could therefore be established with plant density at the emergence of 90–150 plants m 2. In contrast with hemp productions of fibre and seeds, the scientific literature investigating the effects of sowing densities of hemp cultivations destined to harvest inflorescences for cannabinoids or essential oils productions is scarce. The sowing densities are usually way lower than those used in other production typologies. Meier and Mediavilla (1998) reported that the highest yields of inflorescences could be achieved at plant densities of 15 plants m 2 at harvest time, corresponding to a

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sowing density of 5 kg ha 1. García-Tejero et al. (2019) showed in a 2-years experiment in Spain that the productivity of flowers and leaves increased significantly with increasing plant densities from 1.1 to 3.3 plants m 2, 3.3 plants m 2 being the optimal density within the range of the experienced densities. However, the effect of plant density on cannabinoid content was less clear.

3.5

Hemp Fertilization Requirements and NUE

Nitrogen is an essential element in plant biology. A lack of nitrogen availability can lead to significant reductions in plant biomass productivity because of the significant role it plays in plant metabolism, and especially in the photosynthetic apparatus and the effect of nitrogen fertilization on hemp yield has been studied by several authors in a range of environments, with contrasting results. This highlights the influence of other factors on the effects of nitrogen fertilization on crop yields and quality parameters. The environmental conditions (soil fertility, latitude, and climatic conditions), variety choice, and even the raw material considered in these studies can impact the apparent effects of nitrogen fertilization on the crop. In a study performed in Sweden, for example, Prade et al. (2012) reported that N fertilization levels ranging from 0 to 200 kgN ha 1 did not have any significant effect on hemp aboveground dry biomass harvested in September (for use as a biogas substrate), nor between February and April (for use as a raw material for solid fuel production). On the other side, Aubin et al. (2015) reported a positive response of hemp biomass accumulation with increasing levels of N fertilization up to 200 kgN ha 1. These contrasting results were also reported by Amaducci et al. (2015). After analyzing published datasets on nitrogen use efficiency (NUE), measured in kg of biomass produced per kg of supplied nitrogen, there was variation from 7.5 to 67.1 kg 1 (Amaducci et al. 2015). Nevertheless, the most commonly reported responses of hemp biomass production to N fertilization levels are a relatively large increase in biomass yield when N fertilization increased from 0 to 100–150 kgN ha 1 (Finnan and Burke 2013a; Ivonyi et al. 1997; Tang et al. 2017a; Vera et al. 2010), and little additional yield with N fertilization from 150 to 200–220 kgN ha 1 (Amaducci et al. 2002b; Aubin et al. 2015; Struik et al. 2000; van der Werf et al. 1995b). This conforms with Legros et al. (2013), who analyzed large datasets of hemp cultivations and reported that the stem yield stabilizes at 120 kgN ha 1. In a study performed on a wide diversity of environments across Europe, Tang et al. (2017a) concluded that hemp dry biomass production responded strongly to nitrogen fertilization levels ranging from 0 to 60 kgN ha 1. However, higher levels of nitrogen fertilization at 120 kgN ha 1 affected biomass production to a lesser extent in most but not all environments, highlighting the existence of an interaction between environment and nitrogen fertilization levels. Considering the disparity of these studies, the nitrogen critical dilution curve represents an interesting tool for evaluating nitrogen use efficiency and crop requirements as it is relatively independent of environmental factors (Gastal et al. 2015) and driven instead by the

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Fig. 5 Representation of the nitrogen critical dilution curves for four crop species; Cotton, wheat, maize, and hemp. The coefficients used for the calculation of these curves are issued from Tang et al. (2017a) for hemp, from Gastal et al. (2015) for maize and wheat, and Xiaoping et al. (2007) for cotton

genotype. Tang et al. (2017a) established the nitrogen critical dilution curve of the hemp cultivar Futura 75. They concluded that the nitrogen demand of hemp was relatively low compared to other C3 crops and that it was even comparable to C4 crops, as represented in Fig. 5. Critical nitrogen dilution curves are also indicators of the Nitrogen Utilisation Efficiency (NUtE) of a crop, measured in kg of biomass produced per kg of nitrogen uptake. The low critical nitrogen dilution curve of hemp indicates that it utilizes the nitrogen taken up relatively efficiently for producing biomass: Tang et al. (2017a) proposed two main reasons for the high NUtE of hemp. First, the low nitrogen content in the aboveground hemp biomass was mainly explained by the low nitrogen content of the stems (0.5–0.7%), which is a high proportion of the aboveground biomass in hemp, implying that the nitrogen taken up is mainly mobilized towards the photosynthetic organs during the vegetative growth where it participates, through photosynthesis, in carbon assimilation. The second reason proposed by Tang to explain the efficient use of nitrogen in hemp is its high photosynthetic nitrogen use efficiency (PNUE). By modeling the photosynthesis of hemp at the leaf level, Tang et al. (2017b) showed that hemp leaf photosynthesis was relatively efficient compared to cotton or kenaf, especially at leaf nitrogen contents lower than 2.0 gN m 2. By upscaling this photosynthesis model to canopy level, Tang et al. (2018) showed that increasing levels of nitrogen fertilization did not affect the canopy PNUE but instead positively affected the gross carbon assimilation through increased leaf area index (LAI) and specific leaf nitrogen (SLN). The effect of nitrogen fertilization on the quality parameters of the fibre is not clear. Aukema and Friederich (1957), Jaranowska (1964), and Rivoira and Marras (1975) reported that the bast fibre content in hemp stems could be negatively affected by nitrogen fertilization. Van der Werf et al. (1995b) found a slight but significant effect of nitrogen fertilization on the proportion of bark in the stem, with increasing

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levels of N fertilization from 80 to 200 kgN ha 1 inducing a decrease of the bark fraction of the stem of 1.6%. In contrast, Legros et al. (2013) did not find any significant effect of the dose of nitrogen on the fibre content in the stems. Still, they concluded that excess N fertilization was not desirable in a hemp crop, as high levels of nitrogen within the biomass of hemp could lead to difficulties at harvest and during fibre processing. In cultivations aimed at producing high-quality fibre, the amount of nitrogen to be supplied should therefore be precisely determined to reach both optimal yields and quality parameters. The effect of nitrogen fertilization on seed yield has been hardly studied, but for fibre hemp, the effect of nitrogen fertilization seems to depend on the environment strongly. Stafecka et al. (2016) showed positive effects of N fertilization on seed yield from 0 to 90 kgN ha 1, but the extent to which the nitrogen level affected the seed yield varied from year to year. The positive effect of N fertilization on hemp seed yield has also been reported by several authors, for N levels ranging from 0 to 150–200 kgN ha 1 (Aubin et al. 2015; Legros et al. 2013; Maļceva et al. 2011; Vera et al. 2004; Vera et al. 2010). Tang et al. (2017a) reported slight but insignificant increases in seed yields with increasing levels of nitrogen fertilization from 0 to 120 kgN ha 1. The effect of N fertilization on the 1000 seeds’ weight is not clear. However, Stafecka et al. (2016) reported that the N fertilization level could affect the 1000 seed weight in hemp, but these results are in contrast to those of Maļceva et al. (2011). The effect of other macronutrients on hemp yield has poorly been studied, but in general, it seems that phosphorus and potassium have minimal effect on hemp biomass productivity. Potassium application rates from 0 to 150 kg ha 1 did not affect the biomass productivity in a study conducted on four different sites in Ireland (Finnan and Burke 2013b). Similarly, Ivonyi et al. (1997) and Aubin et al. (2015) reported that both potassium and phosphorus fertilization had a minimal effect on hemp biomass yield. Vera et al. (2010) observed that neither phosphorus nor sulfur affected hemp biomass yields. Finnan and Burke (2013b) concluded that the optimal potassium fertilization strategy on soils of medium to high potassium concentrations would replace the amounts of potassium used by the hemp crop.

3.6

Water Requirements and Water Use Efficiency

Hemp is grown during the hot season when water can become a limiting factor to its growth, especially under semi-arid climates characterized by low and irregular rainfall and high evaporative demand. Under such environments, hemp water requirements were reported by Cosentino et al. (2013) to vary between 250 and 450 mm depending on the flowering precocity of the variety. Indeed, early flowering cultivars display a shorter duration of their growth cycle than the late flowering ones, thus requiring less water to complete their cycle. These reported amounts of water requirements in a semi-arid climate corroborated the statements of Ranalli and Venturi (2004) and the findings of Di Bari et al. (2004). These authors and also

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Cosentino et al. (2012) stated that in a semi-arid climate, hemp water requirements are higher than those of soybean, similar to those of sunflower, and lower than those of grain sorghum and concluded that, in such environments, hemp cultivation could not be considered without foreseeing the use of an irrigation system. Because of its deep root system, hemp can take up water from the deeper soil layers where available. However, the crop must be well supplied with water at specific developmental stages. It is essential to maintain non-restricting levels of water availability between sowing and emergence as the processes of germination and radicle/hypocotyl elongation are strongly dependent on soil water availability. Hemp has been reported to be relatively sensitive during its first growing stages (Herppich et al. 2020; Struik et al. 2000), even though this affirmation is not echoed in scientific literature, as the effects of water shortage on a hemp crop were mainly studied after canopy closure, with crops being well-irrigated up to that point (Bahador and Tadayon 2020; Cosentino et al. 2013; García-Tejero et al. 2019). Hemp water requirements also depend on the targeted production. As already discussed, for fibre production, the harvest should preferentially be realized at the stage of full-flowering to avoid the drop in quality of the fibre that occurs during the seed filling process. On the contrary, for seeds, dual or tri-purpose production, the hemp crop is harvested at the stage of seed maturity, about one month later than the full-flowering stage. During this period, water availability is important to increase the efficiency with which the assimilates are translocated from the source to the sink organs. The effect of water availability on the concentration of cannabinoids has been poorly studied. Two recent studies suggest that increasing levels of water availability could have slight and positive effects on the cannabinoid content (Calzolari et al. 2017; García-Tejero et al. 2019). To summarise, three developmental stages of hemp cultivation require particular attention in preserving them from drought stress: germination, from emergence to canopy closure, and during the seed-filling period. Irrigating the hemp seedbed right after sowing and during the phase from emergence to canopy closure can therefore be necessary in case of low water availability, even under non-semi-arid environments (Herppich et al. 2020). In such cases, irrigation providing limited amounts of water (about 10–15 mm) is preferable for avoiding creating anoxic conditions that are poorly tolerated by hemp. This irrigation should also be realized at low intensity to avoid heavy droplets that could cause soil crusting before emergence or damage the juvenile plants susceptible to lodging. The deep root system of hemp should reach water reserves during the rest of the vegetative growth (from canopy closure to full-flowering). However, irrigation practices may still be necessary depending on the nature of the terrain and the meteorological conditions. A good irrigation practice in hemp under semi-arid environments consists of partial restoration of the water requirements. Di Bari et al. (2004) found that the restoration of 66% of the water lost by evapotranspiration was sufficient to reach maximum aboveground biomass yield, while Cosentino et al. (2013) reported that only 50% of restoration of the maximal evapotranspiration (ETm) did not significantly hamper hemp productivity. Therefore, limiting the water supply would result

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in higher water use efficiency (WUE) without affecting productivity. Cosentino et al. (2013) observed WUE values of 1.9 and 2.4 g kg 1 at full flowering and 2.7 and 3.1 g kg 1 at seed maturity, under 100% and 50% of ETm restoration, respectively. Achieving a high WUE is a determinant from both an ecological and economic point of view. This is especially true under semi-arid climates where water is a precious resource. Tang et al. (2018) measured gas exchanges on hemp canopies. They showed that hemp’s photosynthetic water use efficiency at canopy level (PWUEc) increased from 4.0 μmolCO2 mmolH2O 1 under well-watered conditions to 4.7 or 7.5 μmolCO2 mmolH2O 1 under different durations and intensities of water stress conditions. Under short duration, the increase in PWUEc was due to a lowering of the stomatal conductance which resulted in a decreased carbon assimilation and water transpiration, the second being more affected than the first due to the non-linear relationship between carbon assimilation rate and CO2 concentration within the intercellular spaces of the leaves. Under longer duration and stronger intensity of water stress, hemp displayed other responses in addition to the lowering of the stomatal conductance: an increment of the ratio of senesced leaves to green leaves caused a reduction in the leaf area index (LAI), increasing specific leaf nitrogen (SLN) and a reduction of the transpiratory surface, which led to a substantial increment of the PWUEc from 4.2 to 7.5 μmolCO2 mmolH2O 1 when going from a well-watered to a water-stressed condition. However, such conditions of water stress are not desirable during cultivation as carbon assimilation is severely impaired.

3.7

Harvest

Harvesting hemp can be a complicated task that requires good organization and is potentially subject to complications. Harvest date, for example, can be difficult to determine because of hemp’s heterogeneity. The recent rebirth of this crop and the plasticity of its production has led to the development of diverse typologies of harvest and harvesting prototypes and machinery already in use for other crops. We discuss, hereafter, the different modalities of harvest that vary according to the raw material being harvested and the availability of adequate mechanization.

3.7.1

Harvesting Stems for Fibre Production

Harvesting the crop solely for stem production should be carried out at the stage of full-flowering to obtain high-quality fibres with low levels of lignification and secondary fibre. The harvest is relatively simple to perform and does not necessarily require specific equipment, depending on the harvest method. Two harvest methods co-exist today: the so-called “disordered” and “ordered” methods. The disordered harvest is the only one used to any large extent by the growers and does not require specific equipment. In contrast, the second one, developed in the frame of the

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European-funded research projects HempSYS and SSUCHY (Amaducci et al. 2008d), remains today at an experimental stage. The “disordered” harvest consists of a simple mowing of the hemp stems at ground level, which leaves them disordered on the ground. Depending on the height of the crop, the stems may need to be cut into two or three portions to facilitate the successive steps of swathing and baling. The large-scale harvest of hemp has been carried out for a long time with simple cutting bars, especially in France (Amaducci and Gusovius 2010). Prototypes and commercial machines with two, three, or even four concomitant cutting bars have been developed to cut the hemp stems into sections with one passage (Amaducci and Gusovius 2010; Gusovius et al. 2016; Pari et al. 2015). These have provided a time-saving and efficient way of reducing the length of the hemp stem portions, further facilitating the next steps and the primary transformation processes. This harvesting typology also represents an advantage for dew retting, as the stem portions are left randomly distributed on the ground, which allows for a better quality of the dew retting when compared to harvest typologies that immediately swath the stem portions (Amaducci and Gusovius 2010; Gusovius 2002, cited by Gusovius et al. 2016). Several French producers use common silagers for cutting hemp stems into about 40 cm long portions and swathing them simultaneously. However, the most commonly used harvester for this operation remains today the system “HempCut,” developed by the company HempFlax (Oude Pekela, Netherlands), which can be mounted on a typical combine harvester. The stems are cut at ground level by counter-rotating discs mowers and fed into the drum, where they are subsequently cut into 60–70 cm portions and left in swaths (Amaducci and Gusovius 2010), a similar outcome to that of silagers. Another system, the Bluecher 02/03, developed by the company Kranemann (Klocksin, Germany), allows for a similar outcome. The system roughly consists of two counter-rotating vertical elements of cylindrical shape. The hemp stems are cut at ground level, caught by external claws, and brought toward the inner space of these two elements, where they are subsequently cut into 60–70 cm pieces and swathed (Amaducci and Gusovius 2010). The swath can be left in the field for the dew-retting step to facilitate the material’s primary processing (see Sect. 3.8.). The “ordered” harvest represents an opportunity for obtaining raw material that can be processed further in the flax scutching lines. Dedicated hemp facilities for scutching and hackling long and aligned fibre for textile and yarn production are inexistent. The current size of the hemp market cannot justify the development and building of such dedicated processing lines, especially considering the importance of limiting the distance between the cultivation site and the processing facilities, which would require numerous processing facilities or restrict hemp to regionalization of its production. The use of the pre-existing flax processing facilities represents an interesting opportunity for obtaining long and parallel high-quality fibre destined for the production of high added-value end products. These facilities must be fed with aligned stem portions that do not exceed 90–110 cm (Venturi et al. 2007). The lack of harvesting equipment able to leave the hemp stems parallel on the field heavily restricts the possibility of using hemp raw material for obtaining long and ordered fibre of high added value. This issue was partially tackled in the research

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projects HempSys and SSUCHY through the development of an experimental harvester that cut the stems at ground level and subsequently lay them parallel to each other to the motion of the harvester. This said, however, obtaining stem portions of about one meter long is today not feasible and represents a major technical obstacle in using flax scutching and hackling lines for hemp raw material, as the ulterior steps of swath turning and baling can be realized with pre-existing flax equipment (Venturi et al. 2007).

3.7.2

Harvest for Seed Production

Hemp seed production, as already mentioned, requires appropriate choices of cultivar, sowing date, and density for successful cultivation, and the harvest should receive no less attention. The grower must pay careful attention to the developmental stage of the inflorescences. Harvesting too soon could lead to a high proportion of immature and green seeds, while harvesting too late could result in yield losses due to bird predation, seed shattering (Chen and Liu 2003; Schluttenhofer and Yuan 2017) and insect pests (Britt et al. 2019). Mature seeds can be found simultaneously as small, green, and immature seeds within the same inflorescence, leading to seed shattering. This highlights the importance of good cultivation management to reach the highest level of homogeneity of the crop. Seed harvest is usually carried out with a combine harvester, but hemp seeds are fragile and easily broken, so the threshing speed should be reduced accordingly. Damaged seeds are more susceptible to lipid oxidation during storage, affecting the global quality of oil production (Desanlis et al. 2013; Vera and Hanks 2004). Moreover, Desanlis et al. (2013) reported that hemp seed germination rate was negatively affected by increasing threshing speeds. Also, they advised not to tighten the counter beater too tightly, neither too loose. In addition, the cutting height must be cautiously determined to avoid seed losses if set too high and limit the amounts of stems that can be cut and threshed alongside the inflorescences if set too low, as stem fibres will wrap around the inner organs of the harvester, blocking it. After harvest and threshing, hemp seeds must be dried immediately at less than 40  C (Desanlis et al. 2013). A higher temperature could crack or burn the seeds (Callaway 2004). French cooperatives usually recommend drying the seeds within 4–6 h after the harvest, reducing the moisture content from about 20% at harvest to less than 9% after drying.

3.7.3

Dual and Tri-Purpose Productions

Dual-purpose production of stems and seeds is the most common in Europe as it maximizes production by using all the plant fractions, except inflorescences. Nevertheless, a disadvantage of this production method remains in the quality of the fibre produced. In dual-purpose production, hemp is harvested at seed maturity. Therefore, the quality of the fibre does not meet the quality standards required for textile production (Westerhuis et al. 2019), though it can be used for producing paper pulp

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(Kamat et al. 2002; van der Werf et al. 1994b), bioenergy (Prade et al. 2015), or reinforced thermoplastic compounds (Shahzad 2011). The vital issue in dual-productions is optimizing the yield of each fraction. High fibre yields and quality can be obtained by employing a high sowing density and attaining an extended duration of the vegetative growth, as explained in Sect. 2.1. Extending the vegetative growth through crop management also leads to an increased stem height. Harvesting these dual-purpose crops requires the use of adaptation kits that allow the cutting height to be modified, while the rotative organs inside the harvester need to be protected from the fibre that can wrap around them and block the mechanism (Amaducci and Gusovius 2010; Desanlis et al. 2013). As for sole fibre production, the cutting height needs to be precisely determined for limiting seed losses if set too high and limiting the amount of fibre fed in the harvester’s drum if set too low. High amounts of stem taken up by the combine harvester can lead to fiber losses and yield (Chen and Liu 2003). The heterogeneity of hemp amplifies this phenomenon. For a dual-purpose production of seeds and stems, Chen and Liu (2003) proposed adapting a windrower – increasing the cutting height and realizing two separated windrows; one for the inflorescences and another for hemp stems. The Institute of Natural Fibres and Medicinal Plants (Poznań, Poland) also developed a hemp harvester with a similar outcome (Pari et al. 2015). The two swaths can be left to dry and picked up by a conventional harvester equipped with a pick-up header. Two German companies Deutz-Fahr Erntesysteme GmbH (Launingen) and Gerhard Götz GmbH (Bühl), developed a combine harvester that cuts the apical part of the hemp crop, which is then threshed, while the stem is mowed at the same time, cut into 60 cm long sections and swathed. In the case of a tri-purpose production, specific harvesters have been developed. Stems are cut into 60 cm sections and laid in swaths. At the same time, a combine header collects the inflorescences that are threshed in the turbine of the harvester, and the seeds are separated from the flowers, and each fraction is collected separately. This equipment, though costly, may lead to greater sustainability of the hemp sector, as the harvest of the three main fractions of hemp biomass may maximize the incomes of the producers, leading to a lesser dependency on the market prices of the producers’ single products.

3.8

Retting

In the case of fibre production, regardless of the end-use application, stems are usually retted. Retting is a process during which the pectins that bind the fibre cells together at the level of the middle lamella are attacked by micro-organisms that release pectinolytic enzymes (Tamburini et al. 2003). The degradation of these macromolecules ultimately leads to easier decortication or scutching (as it is called at an industrial scale), making it less energy consuming, more efficient, and enables the separation of finer fibres (Booth et al. 2004; Musio et al. 2018). In the past, hemp

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Fig. 6 Hemp stems subjected to different durations of dew-retting, from un-retted stems (top) to 61 days of dew-retting (bottom)

stems were water retted in water basins or dew-retted on the field. The cycles of humidity/drying induced by the morning dew and the precipitations allow for the development of the micro-organism involved in the retting. Retting in water basins has been mostly abandoned, except for east European countries and China (Desanlis et al. 2013; Müssig and Martens 2003), because of its environmental impact and its cost compared to dew-retting (Jankauskiene et al. 2015; Keller et al. 2001), despite it being the more efficient of the two (Jankauskiene et al. 2015). Dew-retting is heavily dependent on weather conditions (Müssig and Martens 2003) and the distribution of the hemp stem on the ground. This can affect the degree of humidity and lead to heterogeneity in the degree of retting (Mazian et al. 2018; Müssig and Martens 2003; Placet et al. 2017) (Fig. 6). Over-retting can also occur if the stems are left for too long, leading to a degradation of the fibre and reducing its quality parameters and the scutching efficiency (Musio et al. 2018; Sharma et al. 2005).

4 Conclusion Hemp production has recently experienced a revival. This phenomenon is driven by several factors, including that hemp can be inserted well into a rotation system through its positive effects on the successive crop. Hemp has the image of a sustainable crop that does not require phytosanitary products. The plasticity of hemp production offers a wide range of potential applications of its raw materials. However, despite this, the development of a sustainable and robust sector is hindered by several bottlenecks. The complex interactions between genotype, environment and crop management render the cultivation of hemp complicated and difficult to optimize. A lack of specialized machinery and the scarcity of dedicated post-harvest processing facilities represent a significant limitation for the producers. Developing a robust scientific understanding of the complex interactions between genotype and environment is critical for optimizing hemp production in given environments. In

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contrast, the development of decision support tools, such as phenology models, would be an appropriate means for achieving efficient communication streams between scientists and producers. At the same time, breeding activities will have a pivotal role to play to reinforce the sustainability of the sector.

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van der Werf HMG (2002) Hemp production in France. J Ind Hemp 7:105–109. https://doi.org/10. 1300/J237v07n02_12 van der Werf HMG (2004) Life cycle analysis of field production of fibre hemp, the effect of production practices on environmental impacts. Euphytica 140:13–23. https://doi.org/10.1007/ s10681-004-4750-2 van der Werf HMG, Haasken HJ, Wijlhuizen M (1994a) The effect of daylength on yield and quality of fibre hemp (Cannabis sativa L.). Eur J Agron 3:117–123. https://doi.org/10.1016/ S1161-0301(14)80117-2 van der Werf HMG, Harsveld van der Veen JE, Bouma ATM, ten Cate M (1994b) Quality of hemp (Cannabis sativa L.) stems as a raw material for paper. Ind Crop Prod 2:219–227. https://doi.org/ 10.1016/0926-6690(94)90039-6 van der Werf HMG, Wijlhuizen M, de Schutter JAA (1995a) Plant density and self-thinning affect yield and quality of fibre hemp (Cannabis sativa L.). Field Crop Res 40:153–164. https://doi.org/ 10.1016/0378-4290(94)00103-J van der Werf HMG, van Geel WCA, van Gils LJC, Haverkort AJ (1995b) Nitrogen fertilization and row width affect self-thinning and productivity of fibre hemp (Cannabis sativa L.). Field Crop Res 42:27–37. https://doi.org/10.1016/0378-4290(95)00017-K van der Werf HMG, Brouwer K, Wijlhuizen M, Withagen JCM (1995c) The effect of temperature on leaf appearance and canopy establishment in fibre hemp (Cannabis sativa L). Ann Appl Biol 126:551–561. https://doi.org/10.1111/j.1744-7348.1995.tb05389.x Venturi P, Amaducci MT (eds) (1999) Canapa (Cannabis sativa L.). Le colture da fibra. Edagricole Venturi P, Amaducci S, Amaducci MT, Venturi G (2007) Interaction between agronomic and mechanical factors for fiber crops harvesting: Italian results–Note II. Hemp J Nat Fibers 4:83– 97. https://doi.org/10.1300/J395v04n03_06 Vera CL, Hanks A (2004) Hemp production in western Canada. J Ind Hemp 9:79–86. https://doi. org/10.1300/J237v09n02_08 Vera CL, Malhi SS, Raney JP, Wang ZH (2004) The effect of N and P fertilization on growth, seed yield and quality of industrial hemp in the Parkland region of Saskatchewan. Can J Plant Sci 84: 939–947. https://doi.org/10.4141/P04-022 Vera CL, Malhi SS, Phelps SM et al (2010) N, P, and S fertilization effects on industrial hemp in Saskatchewan. Can J Plant Sci 90:179–184. https://doi.org/10.4141/CJPS09101 Westerhuis W, Struik PC, van Dam JEG, Stomph TJ (2009a) Postponed sowing does not alter the fibre/wood ratio or fibre extractability of fibre hemp (Cannabis sativa). Ann Appl Biol 155:333– 348. https://doi.org/10.1111/j.1744-7348.2009.00342.x Westerhuis W, Amaducci S, Struik PC et al (2009b) Sowing density and harvest time affect fibre content in hemp (Cannabis sativa) through their effects on stem weight. Ann Appl Biol 155: 225–244. https://doi.org/10.1111/j.1744-7348.2009.00334.x Westerhuis W, van Delden SH, van Dam JEG et al (2019) Plant weight determines secondary fibre development in fibre hemp (Cannabis sativa L.). Ind Crop Prod 139:111493. https://doi.org/10. 1016/j.indcrop.2019.111493 Wheeler M, Williams Merten J, Gordon BT, Hamadi H (2020) CBD (Cannabidiol) Product attitudes, knowledge, and use among young adults. Subst Use Misuse 55:1138–1145. https:// doi.org/10.1080/10826084.2020.1729201 Xiaoping X, Jianguo W, Zhiwei W et al (2007) Determination of a critical dilution curve for nitrogen concentration in cotton. J Plant Nutr Soil Sci 170:811–817. https://doi.org/10.1002/ jpln.200620627 Zegada-Lizarazu W, Monti A (2011) Energy crops in rotation. A review. Biomass Bioenergy 35: 12–25. https://doi.org/10.1016/j.biombioe.2010.08.001

Patenting Journey of Hemp and Development of Various Applications Abhishek Choudhury and Rajiv Kumar

Abstract Hemp is one of the most ancient and miraculous plants, with innumerable uses. Hemp or industrial hemp is an almost non-psychotropic cannabis plant against its highly psychoactive cousin, marijuana. Mainly in the last couple of decades, there has been a sharp rise in the number of publications of both the research/review articles in scientific periodicals and the patent applications, suggesting a significant increase in the research/innovation activity in this area of cannabis/hemp having a vast canvas of applications. The patent literature indicates the invention and innovation activities, which have high business potential. Various innovation-led business enterprises track patent literature more specifically to build their present and future business strategies. Initially, Europe and the USA accounted for a majority of patent applications on hemp. However, recently in the last 20 years, Asia in general and China, in particular, contributed the bulk of patent applications. The major areas of hemp patents include fiber, composites, and machinery (ca. 25%) followed by agriculture and related machinery; health care; food, beverages, nutraceuticals; paper products and leather, textile, each contributing ca. 8–12%. The use of hemp for 3D printing, nano carbon sheets for energy storage, and automotive applications is also growing fast. There may be a significant increase in the use of hemp oil (mainly CBD) for health care (pharmaceuticals/cosmetics), etc. Patent research spanning over a century suggests that innovators have found numerous ways to utilize this plant’s various parts, namely its leaves, seeds, and stalk. The applications of hemp in the areas spanning from pharmaceuticals, textile, construction material, food, beverage and nutraceuticals, cosmetics, fiber, and composites to exotic applications like battery electrodes is expected to grow significantly in the near future. Keywords Automotive · Composite · Hemp · Nutraceuticals · Textile

A. Choudhury Nanobiz India Private Limited, Pune, India e-mail: [email protected] R. Kumar (*) QLeap Academy, Pune, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 D. C. Agrawal et al. (eds.), Cannabis/Hemp for Sustainable Agriculture and Materials, https://doi.org/10.1007/978-981-16-8778-5_5

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Abbreviations CBD FMCG PCT THC WIPO

Cannabidiol Fast moving consumer goods Patent Co-operative Treaty Tetra hydro cannabinol World Intellectual Property Organization

1 Introduction The research-driven scientific activity in a particular area can be reflected by the publication trend of the research findings and inventions. While scientific research is commonly published in journals/periodicals, the inventions are generally published as patents. The patent literature indicates the invention and innovation activities, having high business potential. Various innovation-led business enterprises track patent literature more specifically to build their present and future business strategies. There are three qualifying criteria for granting a patent, namely (i) novelty, (ii) non-obviousness, and (iii) utility of the claimed invention. The details about what constitutes these three criteria for patenting, legal requirements, types of patenting strategies, the life of the intellectual property protection, etc., can be found elsewhere (WIPO 2021). Generally, a patent application is first filed in a particular legal jurisdiction (country), and then the same application can also be filed in multiple countries. However, it must be considered as a single application, be it published or granted. Industrial hemp or hemp (Cannabis sativa L) is a non-psychoactive cousin of cannabis (marijuana). Hemp plants possess a vast canvas of industrial applications such as medicinal, nutritional, cosmetics, paper, fiber (cloths, ropes, bags, etc.), green composites and construction materials (hempcrete), nano-carbon sheets, etc. (Karche and Singh 2019). In addition, hemp, a fast-growing terrestrial plant, captures significant quantities of CO2, almost 2–4 times compared to forest/trees per Ha per year (Toochi 2018; Vosper 2018). Due to its similarity with marijuana, hemp was also banned/restricted for its cultivation, along with marijuana, globally around the 1960s. However, because of recent research and a large spectrum of its industrial applications of cannabis/hemp, the restrictions on its cultivations are being eased out and relaxed in order to promote green industrial materials apart from contributing towards climate change mitigation. Although there are many books, reviews, and research articles on cannabis/hemp (Abel 1980; Small 2017; Russo 2005; Karche and Singh 2019), there are hardly any reviews on the patent literature published on cannabis/hemp (Chaturvedi and Agrawal 2021). The present chapter deals with a detailed and comprehensive review of the hemp patent literature, including patent filing history and trends over

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150 years. Also, the chapter covers the area-wise distribution and detailed analysis of hemp applications to provide an understanding of the past and recent trends as well as the dynamics of the inventive activity of hemp.

2 Methodology A patent search was conducted using the keyword hemp in the title and abstract of the granted patents and published patent applications. It resulted in close to 15,000 patent families (unique inventions) published from 1856 to December 31, 2020. Interestingly, more than 70% of these applications were published only in the last two decades (2001–2020). The patent search was conducted using the patent search and analytics tool Patseer (https://patseer.com). The patents, cited in the text and referred to in the reference list, can be easily retrieved through Google patents (https://patents.google. com/) using a two-letter country code followed by Patent Number. The country codes for few major patenting countries are US for the United States of America; CN for China; WO for PCT Applications; EP for European Applications; JP for Japan; IN for India. The PCT (Patent Co-operation Treaty) is an international patent law treaty concluded in 1970. A patent application filed under PCT can get protection in PCT contracting countries. A patent family may comprise one or more patents/patent applications originating from a single original (priority) application. Therefore, the analysis of the patent family reflects the accurate number of inventions because generally, there is only one invention per patent family. In comparison, an analysis using a raw number of patent publications inevitably involves double or multiple counting because one patent family may contain several patent publications if the applicant files the same invention in more than one country. Hence analysis by the patent family gives more accurate results regarding the level of inventive activity taking place. Therefore, the patent family we considered for the analysis was prioritized as follows: English document—These are mainly US Patents and published patent applications, European Union Patents and published patent applications, or published Patent Co-operation Treaty Applications (PCT). Non-English versions were considered when there was no equivalent English patent family record. The translation was used from the European Patent Office’s Espacenet database (https://worldwide.espacenet.com). This chapter has covered both the quantitative and the qualitative innovation journey of hemp patents from the mid of 1900 century till the end of 2020. It shows the evolution of various application sectors over numerous decades and provides a zoom-in picture of evolution for the last 20 years (2001–2020).

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3 Overall Trends The last six decades in general and the last two decades, in particular, have witnessed an exponential growth of patenting activities concerning hemp. There were 14,910 unique inventions filed across different parts of the world, starting from1856, when the first patent application on hemp was published, till December 31, 2020. While the first two decades of the present century (2001–2020) contributed ca. 70% of the total hemp patents, the last decade alone contributed ca. 54% of the total published hemp patent documents, as plotted in Fig. 1. It can be seen from Fig. 1 that from the first hemp patent, published in 1856, till 1900 (45 years), the yearly average number of patents was ca. 2.6. However, until 1980 (80 years), the average number of patents stood around 33.4 patents per year. From 1980 to 2000, the yearly average of patents was ca. 82. In the next decade (2001–2010), the average was ca. 236/year which further shot up exponentially during the last decade (2011–2020) to average at ca. 812/year. Since the beginning of hemp patenting till 1900, when the yearly average number of patents (2.6/year) has reached nearly the same average (2.2) per day in the last decade (2011–2020). This dramatic increase in patent numbers starting from the 1980s followed by the exponential growth of patenting activity in the last two decades and more specifically during 2011–2020 may be due to various factors like increasing scientific research and social and legal acceptance of hemp for industrial and medicinal purposes. The increasing legalization of cannabis/hemp for health care and industrial applications must have given an impetus for increased publications of both the scientific papers/reviews and patents (Chaturvedi and Agrawal 2021). It may be

10 Year Blocks

20 Year Blocks

Number of Publications

9000

8117

8000 7000 6000 5000

4000

2364

3000

1636

2000 1000

118

666

885

569

555

0 Till 1900

1901-20 1921-40 1941-60 1961-80 1981-00 2001-10 2011-20

Publication Year Blocks

Fig. 1 Hemp-related patent publication trend from 1856 to 2020

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Cannabis/Marijuana

Number of Publications

7000

131

Hemp

6000 5000 4000 3000 2000 1000 0 2001-2004

2004-2008

2008-2012

2012-2016

2016-2020

Publication Year Blocks Fig. 2 A comparison of the patent applications published/granted for Cannabis/Marijuana and Hemp during the last two decades in the block of 4 years Others 16 %

USA 5 % Japan 7 % South Korea 8 %

China 56 %

Britain 8 %

Fig. 3 Hemp-related patent filing trend of major patent originating countries. Others also include some EU countries (France, Germany, and Spain) and Asian countries (India, Indonesia, etc.), contributing 2% or less of total patents

interesting to note that the patenting activity of cannabis/marijuana versus hemp grew together, as can be seen from Fig. 2, where the patent publications are plotted in the block of 4 years in the last 20 years (2001–2020). While the overall number for cannabis /marijuana-related patents was more than that of hemp, the trend remains comparable (Fig. 2). However, another major factor noted was the emergence of China as a major contributor towards hemp patenting. In hemp’s case, the main contributor is China having more than 50% of all the patents published on hemp (Fig. 3). Hence, it is important to find out the geographical locations (country of origin) of the major contributors of the hemp patents. Asian countries are dominating in this space, with 71% of the patents filed from China (56%), South Korea (8%), and Japan (7%). Whereas more than 17% of the filings are from Europe, only 5% of the patents were filed from the United States of America (USA). Though Britain shows an overall 8%

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Table 1 Starting year of Intellectual Property (IP) coverage of select countries in patenting search engines like Patseer used in this study

Country United States of America (USA) Germany France Britain (United Kingdom) India Italy Japan Republic of Korea Spain China Russian Federation

Year 1790 1861 1861 1866 1900 1900 1928 1978 1981 1985 1992

Table 2 Decade wise patents from select major hemp patenting countries Publication Decade Till 1900 1901–1910 1911–1920 1921–1930 1931–1940 1941–1950 1951–1960 1961–1970 1971–1980 1981–1990 1991–2000 2001–2010 2011–2020

Great Britain 64 235 118 186 202 45 70 43 19 2 10 29 39

United States 18 23 34 37 31 57 85 39 2 29 86 211

Japan

China

Republic of Korea

81 268 1017 7303

11 145 532 507

2 1 1 14 33 149 471 266 106

of the filings, there is a decline in patenting from Britain, whereas other European countries like Germany, France, and Spain are still relatively active. It may be interesting to note that patent databases and search engines like Patseer, which we have used, started covering intellectual property (patents) from different years for different geographies. Table 1 provides the year of starting the coverage of select countries (Patseer 2021). Since the patent from China and South Korea started to be covered by databases around the 1980s, the patents from these countries started to change the distribution specifically in the last two decades, as seen in Fig. 3. In Table 2, the decade-wise growth of patents from major countries is compared. There was a significant increase once the patents were included from South Korea and China around the 1980s. In other major hemp patenting geographies, the growth in the number of patents was marginal or even decreased, as in the case of Britain. Since there has been a significant increase in patent activity in the last two decades (2001–2020), we compared the patent applications published/granted during this period concerning the patent originating country and cannabis/

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Percentgae of Patents Published

70 60 Hemp

50

Cannabis/Marijana

40 30 20 10 0 China

United States

Japan

Republic of Great Britain Korea

Others

Major Patent Originating Countries Fig. 4 Comparison of quantum of published patents (percentage) in the last 20 years from various countries in Cannabis/Marijuana vs. Hemp

marijuana vs. hemp. Figure 4 compares the cannabis /marijuana vs. hemp patents originating from major patenting countries in this area. Interestingly, China, South Korea, and few other Asian countries file more patent applications on hemp than cannabis/marijuana. In the USA and few European countries like Britain, Germany file more patents on cannabis/marijuana. However, absolute numbers of the patents related to cannabis/marijuana originating from China outnumbered the patents from the USA. This interesting observation can be explained based on the legal status of cannabis/marijuana vs. hemp in different countries. In the USA, many State Governments have legalized the use of marijuana for medical and recreational purposes. Hence, THC and/or CBD based drugs like Sativex, Dronabinol, Epidiolex, and edibles have been approved by the FDA (Chaturvedi and Agrawal 2021), leading to a significant increase of patenting activity in THC/CBD containing marijuana, as the products are of very value compared to the major products obtained from hemp. Figure 5 exhibits the growth of patenting in the last 20 years (in the block of 4 years) from China and South Korea. It can be seen that the patenting activity of hemp from China and South Korea was comparable during the 2001–2004 block. However, there has been a significant increase in patents originating from China in subsequent years. The same from South Korea remained more or less the same in the last two decades. Figure 6 compares the hemp-related patents originating from Japan, the USA, and the UK in the last 20 years in the block of 4 years. While the patents from Japan decreased steadily, the same from the USA increased significantly. The number of hemp patents from Britain remained almost constant (Fig. 6).

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Republic of Korea

4500 4000 Number of Publication

3500 3000 2500 2000 1500 1000 500

0 2001-04

2005-08

2009-12

2013-16

2017-20

Publication Year Blocks Fig. 5 Hemp-related patent publication trend concerning patents originating from China and the Republic of Korea in the last 20 years Japan

United States

Great Britain

160

Number of Publication

140 120 100 80 60 40 20 0 2001-04

2005-08

2009-12

2013-16

2017-20

Publication Year Blocks

Fig. 6 Hemp-related yearly patent publication trend in last two decades concerning patents originating from Japan, United States, and Great Britain

4 The Patenting Trend in Different Application Areas Researchers have explored the parts of the hemp plant, like its leaves, stalk, and seeds, for various applications. Herein we have divided all the ~15,000 hemp patents and published patent applications into the following categories. i. Fiber, Composite Processing, and Machinery ii. Agricultural Chemicals and Machinery (AgChem)* (WHY *)

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iii. iv. v. vi. vii. viii. ix.

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Healthcare, Pharmaceuticals, and Fast-Moving Consumer Goods (FMCG)* Leather and Textile (Textile)* Paper and Other Chemicals (Paper+)* Food, Beverage and Nutraceuticals (F&B)* Construction Materials Automotive and Miscellaneous

Figure 7 depicts the percent distribution of various hemp product categories mentioned above. Hemp fiber and composites-related patents contribute maximum towards hemp-related patents. The number of patents applications related to health care (Pharmaceuticals/Cosmetics/Nutraceuticals), Food and Beverages, Leather and Textile and Paper Products contribute almost equally (12–8%) followed by Construction Materials (5%) and Automotive Products (3%). Table 3 includes the growth trajectory of different major application areas in the last 80 years. Again, it is clear that the fiber and composites followed by Agriculture and machinery for processing constitute major hemp patents among all hemp products. The last 20 years in general and the last 10 years, in particular, have witnessed exponential growth in almost all hemp product categories. Although the fiber and composites category dominates the patenting activity, agriculture, leather/ textile; food/beverages/nutraceuticals; paper products are also rapidly developing. Other application areas like construction, including 3-D printing filaments and composites for the automotive sector, are also emerging. One of the main reasons behind this brisk patenting activity of hemp-derived products is the unique properties of hemp fiber [both bast (for textile, etc.) and hurd (for composites, construction/automotive)], seed, and cannabidiol (CBD) for health care (food, beverages, cosmetic, medical uses) (Karche and Singh 2019). Further, hemp is one of the most environment-friendly plants capturing large quantities of CO2, a greenhouse gas, compared to trees and forests per acre per year. The reason is

Construction Material 5% Food, Beverage and Nutraceuticals, Miscellaneous Paper and Other Chemicals 11%

Leather and Textile

Automotive 3% Fiber, Composite Processing and Machinery 27%

Agriculture - Chemicals and Machinery 13%

Pharma Healthcare and FMCG 12 %

Fig. 7 Distribution for hemp-related patents and published applications concerning application areas

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Table 3 Application area trend for hemp-related patents and published applications since 1940 Hemp products application category Fiber/composite/ machinery Agri/chemicals/ machinery Pharma/healthcare/ FMCG Leather/textile Food/beverages/nutrition Paper and paper products Construction materials Automotive Miscellaneous

Year blocks 2011–20 2001–10 (10 Y) (10 Y) 2989 762

1981–00 (20 Y) 677

1961–80 (20 Y) 205

1620

361

319

139

87

1365

300

228

140

103

1273 1226 1275 507 228 1035

301 307 301 215 90 347

251 73 251 189 95 287

83 11 83 47 25 114

79 02 79 20 17 75

1941–60 (20 Y) 164

that the hemp plant grows relatively fast; at least two crop cycles per year can be harvested. Further, the hemp fiber is quite long and strong.

5 Analysis of Different Application Areas While in the previous section (Sect. 4), the overall trends of patenting activity concerning different application categories of hemp products are given, this section analyzes the hemp products categories.

5.1

Fiber, Composite Processing and Machinery

More than 35% of total patent documents retrieved in the current study are categorized under this section. This category refers to hemp fibers, making the fiber-based composites and various machinery used to make it. There is a steady growth in patenting activity in this segment, where newer and improved processes and machinery are often being investigated. The last 6 years (2015–2020) show multi-fold growth in patenting for this category. Ecofibe Inc. USA (Ecofibre 2021) and the University of Jefferson, USA, are actively developing nanocomposites based on hemp. Russell and Theodora (2019) described a composite material containing nanocellulose and hemp, where hemp is taken from hemp bast fibers, hemp inner fibers, hemp shives, hemp leaves, hemp seeds, or grounded hemp. This composite material is used for making construction blocks or coatings, or textile fabric. Sunderland (2019) developed an antibacterial nanocomposite material having

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hemp oil with a CBD concentration of 10 mg/ml and a biodegradable polymer. Hemp contains more than 450 phytochemicals having antibacterial, antiinflammatory, antifungal, anti-toxicity, quick-drying, and deodorizing effects. Because of such an overwhelming nature of advantages, hemp is used for making functional textiles, clothing, and functional building materials. Yong (2020) optimized technology where hemp is used in a certain way to maximize its process efficacy. The process involves first steam drying the hemp fibers, followed by crushing them multiple times. A freezing step follows each crushing step, and the same freezing and crushing cycle continues until the hemp particle size reaches 180–250 nm. Giovanni (2019) patented a hemp-based composite that can be used for additive manufacturing (3-D Printing). Granular shive from hemp and/or flax with a particle size of 0.1 mm is dispersed homogeneously into a thermoplastic resin. A high amount of hemp particles is used compared to the resin, resulting in a lightweight composite material at a cheaper cost.

5.2

Agricultural Chemicals and Machinery

Close to 2000 patent applications were published in the last two decades, where more than 50% of these patents were filed just in the last 5 years. The patent publication trend shows a growing trend of innovating hemp cultivation, processing, and using hemp as fertilizer and pesticides. Ghalili and Borja (2018) patented a slowrelease fertilizer composition that contains cannabidiol (CBD) oil, tetrahydrocannabinol (THC) oil, and hemp oil derivatives in combination with a superabsorbent polymer(s) (SAP’s). This composition is also used for controlling pests and insects. Szeman and Madlung (2020) filed a patent application where a hemp fiber-based mat is used as a biodegradable substrate to support seeds’ growth. This mat contains 70–95% hemp fibers and 5–30% of another biodegradable thermoplastic polymer.

5.3

Healthcare, Pharmaceuticals, and Fast-Moving Consumer Goods (FMCG)

Hemp and mainly hemp-derived chemicals CBD and THC are widely used for healthcare and pharmaceutical applications. Hemp seed oil is also an important ingredient for numerous cosmetic products. Patent publication for this domain shows an exponential growth for the decade starting 2011. Powdery extracts of the hemp plant provide unique electronic properties and have an excellent favorable toxicity profile, making them more complementary to cosmetic products than other bio-based ingredients or conventional talc products (Palaio 2020). Palaio (2020) developed a method of micronizing hemp flour derived from hemp hurd or a hemp seed shell and using them to make cosmeceutical compositions.

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Ansari et al. (2018) filed a patent application using hemp seed oil to make an oral care composition. Lincoln (2019) used hemp seed oil to make a moisturizing composition. Malhotra (2019) described a composition made of hemp seed oil and a water-soluble polymer for making lubricating strips for shaving devices.

5.4

Leather and Textile

Usage of hemp fibers in textile is found for both woven and non-woven fabrics. Hemp fabrics are more durable compared to cotton fabric. A combination of hemp and cotton fabric is also a popular choice. Environment-friendly masks made up of hemp fabric are currently in fashion. Leather and textile have exponential growth in patenting between 2011 and 2015. After 2015, there is a bit of drop-in patenting activity that seems momentary, and one might see another jump in patenting by the next 5 years. Zhang et al. (2016) developed a method for making three-component interweaved fabric having mulberry silk, hemp, and wool. This fabric has excellent mildew resistance, moisture absorption, air permeability, ultraviolet resistance, radiation resistance, electrostatic prevention, and antibacterial property of hemp fibers. Mulberry silk brings in softness and smooth, delicate hand feeling wherein wool is responsible for good elasticity. Ma and You (2020) disclosed a method of making hemp fabric-based textured sportswear. It has excellent moisture absorption, ultraviolet resistance, good breathability, and good hand touch feeling. Baer and Miller (2018) patented a water-dispersible non-woven tissue or a wet wipe made up of hemp plant-based individualized bast fibers. Sirotic (2019) described a personal hygiene product where an absorbing layer is made of cotton and hemp fibers. Kinagi and Vaidya (2020) disclosed a hand-woven hemp shoe that has excellent antibacterial and antifungal properties. Khubani (2020) dispersed hemp fibers with a compression garment (e.g., glove, posture support garment, pants, leggings, tights, shorts, long sleeve top, short sleeve top, sock, etc.). This helps improve the durability of the compression garment and imparts other properties like anti-microbial or antibacterial, mildew-resistant, odor reduction, moisture-wicking (absorbing moisture through capillary action), etc. Jung et al. (2019) patented an eco-friendly process of producing hemp fibers, including an enzymatic treatment process and a microorganism treatment process. Seok et al. (2019) patented a gold or silver coated hemp fabric. This helps in mitigating bacterial propagation in the fabric as well as retains soft texture and warmth. The method of manufacturing involves a two-step process. In the first step, hemp fabric is wet coated with collagen or cellulosic primer, followed by the sputtering process of deposition of gold or silver nanoparticles.

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5.5

139

Paper and Other Chemicals

More than 2000 patent publications are categories under this section. This covers majorly paper applications of hemp and different chemicals that are extracted from hemp. Paper products made of hemp pulp shows excellent electrical insulation property. The last decade (2011 onwards) shows the exponential growth of patenting in this segment. Xu et al. (2020) invented a high-voltage low-impedance electrolytic capacitor paper containing hemp, wood, and cotton pulp. The resulting paper has excellent tensile strength, flexibility, insulative, and voltage resistance. Lee and Kim (2020) filed a patent application to make wallpaper using hemp, where hemp fibers are first to cut into 2–3 cm long strips. These cut hemp fibers are added to an aqueous sodium hydroxide solution, and the same is cooked. This step is followed by washing, neutralizing, and dissolving the cooked hemp fibers. This is further mixed with Korean handmade papers to make a final wallpaper.

5.6

Food, Beverage and Nutraceuticals

The use of hemp seed oil and proteins in making food preparations, beverages, and nutraceuticals is gaining popularity. A big jump in patent publications is seen post 2010. Casper and Maheshwari (2020) formulated a food composition based on hemp protein, other proteins, and starch. These food products are very crunchy and have good storage stability. Spickermann et al. (2020) invented a process for preparing hemp seed extract that can be used as a flavoring agent in food and beverages. Samaranayaka et al. (2019) claimed a method of extracting hemp seed protein and making stable emulsions for microencapsulating lipid-based components. Graham et al. (2019) filed a patent application that describes preparing tofu-like products using hemp milk. Gamble (2020) made an infant formula that contains non-soybased proteins. It contains chia protein, hemp protein, and free amino acids. Lee (2020) developed a seaweed-based snack where seaweed forms the base edible adhesive glue, hemp powder as a food-grade additive adhering to the adhesive paste, and hemp oil applied on the edible adhesive paste. Inventors also tried making various beverage products, including hemp-based beer and alcohol, cola products, and yogurt (Dabija and Oroian 2020; Kaniewski et al. 2020; Erfinder 2020; Yun 2020; Garzon 2020).

5.7

Construction Materials

Using hemp composite as construction materials is a known concept. It shows an up and down patent publication activity which suggests that innovators are trying to

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explore hemp for use in construction activities but are not much convinced yet. It might take a few years by the time hemp gains significant impetus to be used as a construction material. Talukdar et al. (2020) patented a concrete material that is made from hemp straw ash. These concretes are used for lower strength applications. A building product (a board), patented by Robinson and James (2020), is made from a mixture of hemp fiber with clay or lime-based binder. Knott (2020) filed a patent application that demonstrates manufacturing a foamed plaster that used powdered limestone and hemp fiber. Wilson (2019) patented a hemp laminate structure made by multiple adhesively bonded and pressed hemp strands. Kander (2019) patented a hemp nanocomposite that comprises a polymer and carbonized hemp filler.

5.8

Automotive

Hemp fibers and composites are widely used for automotive applications. A little over 300 patent references were retrieved in the current study. The last decade, from 2011–2020, shows 2.5 times more published patents than that of 2001–2010. Though 2017 and 2018 show a slight dip in patenting, an upward stagnating trend is observed for 2019 and 2020. Chilvers (2020) described a hemp foam that can be used for making car seats. Madeswaran et al. (2014) developed a process for making cost-effective, environmentally friendly motor vehicle brake pads of hemp fiber composite. Kieltyka and Kotha (2003) disclosed a vehicle door panel with a decorative cover made up of a blend of natural fibers with hemp. Isamu et al. (2010) patented a multilayer board for a vehicle interior, where the base layer is made up of a composite material with bamboo fiber, cotton fiber, and hemp fiber alongside a biodegradable resin. Ribes and Raybaud (2014) patented a protective screen for an automobile made up of polypropylene and hemp. Kim et al. (2020) patented an eco-friendly automotive interior material with 47–86 wt% of vegetable hemp fibers, 7–29 wt% of thermoplastic fibers, and 5–33 wt% of a binder. Son et al. (2020) patented a process for making a hemp composite that can be used for automotive trim application. This eco-friendly composite is made by impregnating a cut flax fiber or hemp fiber in a polypropylene dispersion solution grafted with maleic anhydride; followed by a dehydration drying process; a fiber separating/dividing process is carried out by a scutcher then mixing polypropylene fibers to form a web followed by needle punching to form a non-woven fabric and heat-press to get the final composite.

5.9

Miscellaneous

Close to 2000 patents and published patent applications could not be classified distinctly in the categories above. These are covered in this miscellaneous section.

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These include the use of hemp in electrical appliances, filtration media, battery electrode separators, conductive inks, tampons, and many recently developed innovative non-traditional applications. It shows an upward trend in the last 5 years, suggesting that innovators may keep exploring many more new applications of industrial hemp for social wellness. Sunderland (2020) discovered hemp-based conductive ink, where the size of the carbonized hem is reduced by milling to 2–5 microns and combined with a waterbased carrier to make conductive ink. Romano (2020) filed a patent application where hemp fiber makes a biodegradable cup to drink hot or cold beverages. Milanova (2020) describes a tampon for absorbing menstrual flow, where the tampon body is made up of industrial hemp fiber which shows superior absorbance of body fluid. These tampons are preloaded with a specific amount of cannabidiol which helps in treating menstruation-related symptoms. Srinivasan et al. (2019) patented a rubber composition for tire and tire component applications containing hemp oil. They figured out that hemp oil improves the tear resistance of the rubber and can produce long-lasting tires. Crippen (2019) explored the potential of using industrial hemp as a filtration medium for faucet attachments, mechanical oil filters, or home air conditioning systems. They reported that a trace amount of non-psychoactive cannabinoids available throughout the hemp plant could show 99% anti-microbial efficacy. They also advocate that industrial hemp is costeffective and easier to work with than commonly used filtration methods like ultraviolet or chlorine-based treatments. Masakata (2003) described the construction of a battery electrode separator where hemp paper is used along with polyethylene to reduce the rate of rupture of the separator film in the event of temperature rise.

6 Conclusion We found that hemp/industrial hemp is attracting an increasing number of researchers and innovators, both from academia and industry, as hemp can be widely used for various application areas. Although hemp patenting started in the 1850s (1856), there was little growth during the early twentieth Century. The patenting activity significantly increased during 1980–2000, when China and South Korea were included in patent search engines like Patseer, used in the present study. Although the beginning of the twenty-first Century witnessed a relatively sharp increase in patenting activity and an exponential increase observed during the last 10 years (2011–2020), probably propelled by increasing acceptance and legalization of hemp cultivation for industrial, research, and health care. China is leading the activity of hemp patenting. The main application area of hemp patenting remains fiber, composites, and machinery (25%), followed by agriculture and related machinery; health care; food, beverages, nutraceuticals; paper products and leather, textile, each contributing ca.8–12%. The use of hemp for construction and automotive applications is also growing rapidly. It is expected that the use of hemp will increase in these areas.

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There may be a significant increase in hemp oil (mainly CBD) for health care (pharmaceuticals/cosmetics, etc.). Additionally, it is further expected that innovative and novel applications of hemp-based materials like energy storage (battery), 3-D printing material, phytoremediation, and pollution control may increase in the near future. Acknowledgments The authors thank Prof. Dinesh Agrawal, Chaoyang University of Technology, Taiwan for helpful suggestions to improve this article.

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Industrial Hemp and Hemp Byproducts as Sustainable Feedstuffs in Livestock Diets Kristine Ely and John Fike

Abstract Cannabis sativa, more commonly referred to as industrial hemp, has been used for fiber, food, and medicinal purposes for millennia. Temporarily suffering a setback for parts of the 20th and 21st centuries, interest in hemp production has resurged with the recent rollback of legislative restrictions. Most notably, an interest in the nutritional profile of hemp seed has developed based on its rich array of fatty acids and protein. The increase in hemp production has led to a reciprocating increase in the availability of hemp seed and its associated by-products. While anecdotal and historical accounts exist for feeding hemp to livestock, published reports are limited. This is further complicated by a lack of acceptance in many countries for feeding hemp to livestock. Livestock’s ability to consume unusable waste products from various commodities and turn them into consumable goods is a major component of sustainable agriculture. Research indicates that dietary enrichment with hemp has the potential as a valuable source of protein, fat, and fiber to increase the quality and composition of meat, milk, and eggs; however, to what extent remains unknown. This review aims to explore the nutrient profile of the industrial hemp plant and evaluate our current understanding of hemp used in livestock diets. Keywords Hemp · By-product · Livestock feed

Abbreviations AA ADF ADG ALA BP

Arachidonic acid Acid detergent fiber Average daily gain α-Linolenic acid Before present

K. Ely · J. Fike (*) School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, USA e-mail: jfi[email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 D. C. Agrawal et al. (eds.), Cannabis/Hemp for Sustainable Agriculture and Materials, https://doi.org/10.1007/978-981-16-8778-5_6

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CHO CP DHA EPA GLA LA NDF PDCAAS PUFA TDF TDN

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Carbohydrate Crude protein Docosahexaenoic acid Eicosapentaenoic acid Gamma linolenic acid Linoleic acid Neutral detergent fiber Protein digestibility–corrected amino acid score Polyunsaturated fatty acids Total dietary fiber Total digestible nutrients

1 Introduction Traditionally thought of as a fiber crop, hemp (Cannabis sativa L.) also has a long history of use for nutritional and medicinal purposes (Small 2015). Hemp consumption and cultivation of grain dates back thousands of years—with wild harvests beginning perhaps 8500 BP (Li 1974) and active cultivation occurring by about 6000 BP (Chen et al. 2009). A foundational grain for the early civilizations that developed in modern-day China (Lee et al. 2007), hemp was ultimately supplanted by other grain crops, perhaps due to differences in yield, ease of harvest, sensory characteristics, or some combination thereof. Still, hemp likely persisted in the diet as a snack and may have been a routine portion of peasants’ diets or a source of sustenance during times of famine (Clarke and Merlin 2013; Small 2017). Although hemp fell from use as a staple food or feed crop, it became increasingly important in the global North as a source of strong, lightweight fibers—particularly for rope and sails—and that remained the case until the late nineteenth century. Hemp’s decline as a fiber crop through the late 19th and early 20th centuries was propelled by the end of slavery, the rise of steam-powered ships, and the availability of cheaper fiber sources (Fike 2019). Industrial hemp’s subsequent banishment in much of the West was based on its kinship to psychoactive marijuana, and as such, all-things Cannabis became verboten. In the USA, this began with the passage of the Marihuana Tax Act of 1937 and later with the Controlled Substances Act in 1970. All told, there was a roughly 80-year hiatus in hemp production in the USA. As the legal restrictions against hemp have been rolled back, the resurgent interest in hemp production has been based on the crop’s potential to meet needs for fiber, food, and medicine. A growing interest in the nutritional qualities of hemp seed has led to hemp production as a broad acre food/feed crop—this is largely a tweenth/ twenty-first century construct—and as a result, a variety of grain-based food and personal care products have come to market. Ironically, hemp grains and by-products remain restricted for livestock use, awaiting safety testing and subsequent regulatory approval.

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The possibilities for hemp as a food or feed remain constrained—both because of the regulatory status surrounding feeding and because the volume of hemp grain products available remains limited. Livestock have long been viewed as an integral part of sustainable agriculture (Salami et al. 2019), and in a hemp context, they may be consumers of primary products (e.g., grains) or of crop or processing residues. The ability to recycle nutrients from unusable crop residues and by-products and turn them into high-quality consumable products is a valuable part of any sustainable agriculture system (Oltjen and Beckett 1996). As opportunities for livestock feeding increase, one might expect that this will help drive greater hemp production and use. The growing interest in hemp grain has occurred with the recognition that the seeds are nutritionally dense and contain a number of unique and beneficial nutritional constituents. This review aims to focus on the nutritional benefits of the industrial hemp seed, with some reference to the vegetative parts of the plant as forage or as a potential by-product feedstuff for livestock diets. We touch only briefly on the importance of cannabinoids in industrial hemp production concerning feed resources. Although in some circles, the cannabinoids may be the primary driver of interest in hemp, a larger treatment is outside the scope of this review since their effects are primarily physiological and not nutritive.

2 Nutritional Properties of Hemp Seed From a clarity and consistency standpoint, it is important to note that hemp seed is not truly a seed but is technically defined as an achene (Fig. 1). As with sunflower (Helianthus annuus) “seeds,” the true “seed” of a hemp grain is surrounded by an outer covering, the pericarp, which is more generally called the hull (Clarke and Merlin 2013). However, throughout this publication, we will use conventional/ common parlance and refer to the achene as a seed.

Fig. 1 Anatomy of Cannabis sativa achene. Pericarp (“hull”) with embryo fragments still attached (left), a crosssection which illustrates the white embryo (or “hemp heart”) in the center (middle), intact achene (right). Photo courtesy of David Westerman

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Nutritional properties of hemp seed can vary based on a variety of factors including cultivar, growing conditions, and geography. Despite these variations, whole hemp seeds typically contain 20–30% protein, 25–35% oil, 25–35% carbohydrates, along with beneficial vitamins and minerals (Deferne and Pate 1996; Callaway 2004; House et al. 2010). Hemp seed meal, sometimes referred to as flour, is typically produced by pressing whole hemp seeds. Removing the majority of the oil fraction increases the concentration of the other components and results in a meal with 30–50% protein, 20–40% fiber, and 10% residual oil (House et al. 2010). Dehulling hemp seeds removes about 75% of their fiber; leaving the remaining hemp “hearts” as a concentrated source of protein and oil, with values between 30–40% and 40–50% respectively (Wang and Xiong 2019; Leonard et al. 2020).

2.1

Fat Concentrations and Fatty Acid Profile

Fat in hemp seed represents the most valuable nutritional component (Farinon et al. 2020). Hemp seed has a moderately high oil fraction, with fat comprising 25–35% of the seed’s total weight (Callaway 2004). This places hemp seed between soybean (Glycine max; 20%) and higher-fat oil seeds like flaxseed (Linum usitatissimum) and sunflower seed (>35%; Williams 2005). Some variation in composition occurs due to cultivar, geography, and growing conditions (Irakli et al. 2019). Hemp seed oil is considered of superior nutritional value because it contains elevated amounts of polyunsaturated fatty acids (PUFA; Small 2015). Linoleic acid (LA) and α-linolenic acid (ALA) make up 50% and 20%, respectively, of PUFA present in hemp seed oil (Deferne and Pate 1996; Klir et al. 2019). Because neither LA nor ALA can be synthesized in mammals; they must be consumed in the diet; thus, they are essential fatty acids. Both of these essential fatty acids serve as precursors to eicosanoids, powerful, short-lived chemical messengers that regulate inflammatory processes in the body (Watkins et al. 2005). LA is the primary fatty acid in the ω6 PUFA pathway that produces arachidonic acid (AA), the fatty acid responsible for the production of inflammatory metabolites. ALA is the primary fatty acid in the ω3 PUFA pathway, responsible for synthesizing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both EPA and DHA are important precursors to anti-inflammatory metabolites and are often targeted for dietary manipulation. A normal and healthy balance of inflammatory and anti-inflammatory molecules is necessary during cell repair and muscle growth. In fact, inflammation is an essential part of the host’s defense against pathogens. Inflammation is typically only a concern during disease states (e.g., rheumatoid arthritis, obesity, metabolic syndrome, etc.), when if uncontrolled it can lead to permanent tissue damage. Modern western diets tend to have a ratio of ω6:ω3 fatty acids in excess of 10:1 due to reduced ω3 consumption and increased consumption of grains high in ω6 (Simopoulos 2006). The importance of fatty acid ratios was first illuminated in the 1970s when researchers observed a lower incidence of coronary heart disease in cultures in which omega 3 fatty acid consumption was more prevalent, and often fish

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was the primary source of protein (Keys 1970; Bang et al. 1976). Since then, numerous studies have associated low dietary ω6:ω3 ratios (closer to 1:1) with fewer incidence of heart disease and diabetes (Saini and Keum 2018). Apart from flaxseed, many commonly consumed grains—e.g., corn (Zea mays), soybean, wheat (Triticum aestivum), etc.—have ω6:ω3 ratios in excess of 20:1, whereas hemp seed has a ω6:ω3 ratio closer to 3:1, making it a good dietary alternative compared to modern fatty acid sources (Oseyko et al. 2019). There is interest in adding hemp to livestock diets to produce ω3-fortified meat, milk, and eggs and thus increase human intake of ω3. In addition to being a good source of essential fatty acids, hemp seed also contains gamma-linolenic acid (GLA), a unique ω6 fatty acid that instead has antiinflammatory properties (Kapoor and Huang 2006). Few plant resources besides hemp contain GLA; the primary other sources include black currant (Ribes nigrum), evening primrose (Oenothera biennis), and borage oil (Borago officinalis). Major grain seeds lack GLA altogether. Although acute inflammation is vital to muscle and tissue repair in the body, excessive and chronic inflammation can lead to disease states including arthritis, diabetes, heart disease, and cancer (Serhan and Savill 2005). Thus, eliminating inflammation is not the goal, but rather developing diets that support positive inflammatory responses. The presence of GLA, combined with an ω6:ω3 ratio of around 3:1, makes hemp seed oil an attractive alternative as a fatty acid supplement.

2.2

Oil Quality

Although dietary PUFAs are beneficial for human health, these FA are also more unstable and thus more susceptible to oxidation (Dimić et al. 2009). However, hemp also contains naturally occurring antioxidants that provide oxidative stability to hemp seed oil (Abuzaytoun and Shahidi 2006), e.g., dietary tocopherols, generally referred to as Vitamin E, impart health benefits by scavenging free radicals. This prevents oxidation of fatty acids and damage to DNA, lipids, and proteins, and results in a lowered risk of degenerative diseases including cancer, cardiovascular disease, and age-related macular degeneration (Liang et al. 2015; Irakli et al. 2019; Izzo et al. 2020). Hemp seed has moderate levels of total tocopherol, primarily αand γ– isomers, and concentrations typically range from 55–90 mg/100 g of oil (Farinon et al. 2020). Oxidative stability and quantity of oil recovered are both impacted by harvesting and processing methods (Farinon et al. 2020). Oil quantity and quality frequently also are reduced by uneven field ripening, which leads to inconsistency and a lack of homogeneity of the harvested crop (Deferne and Pate 1996). The presence of chlorophyll and elevated moisture in immature seeds gives the resulting oil a greenish hue post-extraction and further negatively influences oil quality due to increased fatty acid oxidation and degradation (Abuzaytoun and Shahidi 2006).

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Cold press extraction is the current industry standard for hemp seed oil production. However, while cold press extraction retains the crop’s natural antioxidant compounds that improve oxidative stability, it is less efficient than solvent-based extraction methods that extract a greater quantity of oil but are more costly (Dimić et al. 2009; Uluata and Özdemir 2012; Devi and Khanam 2019). Although this might improve the nutrient profile of the resulting hemp seed cake, more work is currently underway to establish better harvesting and extraction methods to both increase oil yield and preserve oil quality (Devi and Khanam 2019).

2.3

Protein Concentrations and Amino Acid Composition

Hemp is a high-quality source of digestible protein with a desirable amino acid composition (Tang et al. 2006). The protein content of whole hemp seed generally ranges between 25 and 30% and is composed primarily of edestin and albumin, both highly digestible globular proteins (Callaway 2004). A protein-rich hemp seed cake which is 30 to 50% protein remains following oil extraction and has potential for use in the livestock industry as a protein supplement (Russo and Reggiani 2015). However, because the dehulling process lacks refinement, hemp seed cake also contains ~10% fat. This increases the energy value of hemp seed cake, yet it potentially creates storage concerns due to oxidizable fatty acids (Mamone et al. 2019). Hemp protein can be further concentrated by removing water-soluble, non-protein components. The resulting hemp protein concentrate is about 65% protein. The most purified hemp protein product, hemp protein isolate, requires additional removal of non-protein constituents, resulting in a product that is 90% protein and primarily utilized to add nutritive value and serve as a functional ingredient in formulated foods for human consumption (Wang and Xiong 2019). Protein quality is quantified based on amino acid composition and digestibility because humans and animals do not have a protein requirement per se. Rather, readily available amino acids are needed for growth and system function. Genetics, growing conditions, and postharvest processing methods all influence protein quality (House et al. 2010). Of available commodity feed grains, soybean is the main protein source included in livestock diets and many human food products. Soybean has relatively high protein content, suitable amino acid profile, and a high digestibility (Dei 2011). These traits and their utility in feeds and food products have led to soy’s widespread production and relatively low cost. It is understandable, then, that studies evaluating hemp protein quality often make comparisons with the nutritional profile of soybean. Similar to soybean, hemp protein is “complete” in that it contains all essential amino acids; however, lysine is the first limiting amino acid with lower concentrations than those in soybean (Wang et al. 2008; House et al. 2010). Whole hemp seed digestibility is lower than that of soybean but still relatively high (84–86%), and digestibility is increased as hemp proteins are concentrated through processing (House et al. 2010). Fiber also influences the digestibility of hemp protein.

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Removing the hull from hemp seed increased protein digestibility from about 85% for whole seed to 95% for dehulled hemp seed, while hemp seed meal, which typically includes the hull, had only slightly greater protein digestibility (about 87%) compared with whole seed (House et al. 2010). Protein digestibility–corrected amino acid score (PDCAAS) allows for better comparison between studies and is the preferred method for protein digestibility measurement (Schaafsma 2000). The PDCAAS was 0.51 for whole hemp seed, 0.61 for dehulled hemp seed, and 0.48 for hemp seed cake (House et al. 2010), much lower than 0.91 reported for soybean (Schaafsma 2000). The limitation of hemp protein is its lysine concentration. Without efforts to breed hemp for increased lysine content, the crop’s protein values will likely remain static and of lower value than protein from soybean (House et al. 2010). While the work of House et al. (2010) provides an early reference on hemp protein value, some caution should be used when extrapolating digestibility values. Most are configured based on human reference data, and digestibility for the intended species will likely vary (House et al. 2010). However, even though lysine is somewhat limited, hemp’s high digestibility and overall amino acid profile make it an attractive alternative protein source for livestock diets.

2.4

Carbohydrate and Dietary Fiber

Carbohydrates (CHO) and fiber make up a large fraction (25–35%) of the total nutrients in hemp seed. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) are often used to measure fiber in livestock diets. Both values are also useful to calculate total digestible nutrients (TDN), a combined value from the measure of CHO, fats, and protein, to estimate the useful energy content of feedstuffs (Coffey et al. 2016). House et al. (2010) reported whole and dehulled hemp seed had about 32% and 8% NDF and about 24% and 3% ADF, respectively; indicating that hemp hulls contain majority of the grain’s fiber. Studies of hemp hulls suggest NDF levels between about 50 and 65% and ADF between about 38 and 50% (House et al. 2010; Kim and Nyachoti 2017; Kim et al. 2018). Hemp seed cake, the product of extracting oil from hemp seeds, includes the hull; thus, greater NDF and ADF values are expected. Halle and Schöne (2013) measured NDF, ADF, and lignin in hemp seed cake at about 45%, 30, and 12% respectively. Some studies do not measure NDF and ADF individually but instead report the total CHO and total dietary fiber (TDF) of hemp seed (Farinon et al. 2020). TDF in hemp seed primarily consists of insoluble dietary fiber, which can also be measured through NDF (Farinon et al. 2020). Therefore, it might be assumed NDF could be a reasonable measure of TDF in hemp seed, making a comparison between studies feasible. Most of the fiber in hemp seed is concentrated in the hull, and many by-products with high levels of fiber are fed directly or used as ingredients for livestock feeds and supplements. Dietary fiber is an important contributor to healthy rumen function and

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gut microbiomes, but more work is needed to determine the nature and effects of hemp seed fiber in livestock and equid (horses, ponies, etc.) diets.

2.5

Anti-Quality Components

Despite many nutritional benefits, hemp seeds also contain antinutritional factors that may impact the digestibility and absorption of nutrients (Russo and Reggiani 2015). Phytates, trypsin inhibitors, condensed tannins, cyanogenic glycosides, and saponins all have been measured in hemp seed and resulting flours (Farinon et al. 2020). These naturally occurring secondary plant defense compounds can negatively affect livestock production through reduced bioavailability of minerals and proteins or digestion to toxic metabolites. It must be mentioned that such constituents typically only present problems for livestock when consumed at excessive levels. However, at low levels in the diet, many of the compounds benefit animal health (Provenza 1995). In humans, consumption of these plant secondary metabolites has preventative effects on diabetes, cardiovascular diseases, and cancer (Pojić et al. 2014). However, appropriate dosages generally have not been determined, thus, minimizing intake of these compounds is considered safest. Heating, soaking, diluting, or supplementing digestive enzymes have all been used to reduce the level or effect of these constituents (Popova and Mihaylova 2019). Primary concerns about the suitability of hemp seed in livestock diets center on their high phytate levels relative to other commonly supplemented oilseeds. Phytic acid, the major storage form of phosphorus (P) in seeds, grains, nuts, and legumes, easily forms bonds with minerals (e.g. zinc, iron, magnesium, and calcium) and proteins to form insoluble salts, rendering these nutrients unavailable to the animal (Popova and Mihaylova 2019). Bacteria in ruminants and hindgut fermenters produce phytases that typically unlock this stored P, but phytate can pose a problem for monogastric animals which lack sufficient microbial populations and levels of this digestive enzyme. Hemp seed and soybeans have similar levels of phytate, however, feeding hemp seed meals or flour may present issues as they have greater (>5%) phytate concentrations (Russo and Reggiani 2013; Galasso et al. 2016; Mattila et al. 2018; Schultz et al. 2020). To overcome challenges with phytic acid and increase P digestion, diets can be supplemented with phytase. E.g., P digestibility increased when pigs fed hemp hulls were supplemented with phytase (Kim et al. 2018); however, such studies with whole seed are lacking. Phytate levels vary by cultivar and growing conditions and tend to correlate positively with the antinutritional factors mentioned above (Russo and Reggiani 2015; Galasso et al. 2016). Breeding and selection for reduced phytate levels could be beneficial for developing hemp seed cultivars intended for livestock feed.

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3 Nutritional Characteristics of Hemp as a Roughage Source Producing oil, meal, fibers, or biomolecules from hemp generally requires further processing, and the associated waste products (e.g., leaves, stems) from the processes might have utility as roughage sources for livestock. Although published literature regarding livestock feeding trials is lacking, whole hemp plants, seeds, and hemp by-products historically have been fed to livestock around the world. Hemp growers in rural China traditionally fed fresh hemp leaves to pigs and other livestock (Clarke and Diemenstraat 1995). Water buffalo (Bubalus bubalis) graze wild Cannabis sativa plants in Pakistan (Ahmad and Ahmad 1990). Nigerian farmers feed hemp leaves to goats to stimulate appetite (Bamikole and Ikhatua 2009). Although literature regarding hemp’s suitability as a roughage source is limited, these anecdotal reports suggest its potential value.

3.1

Hemp Byproducts

By-products created from processing commodities (e.g., brewers and distiller’s grains, citrus and beet (Beta vulgaris) pulp, wheat and cereal grain middlings, and oilseed hulls or meals) represent significant constituents for livestock feeds and feed products. Upcycling of nutrients helps create a market for by-products, turning what would otherwise be a waste product into feed ingredients is an important way to “upcycle” nutrients, creating new markets and additional profits for commodity producers and suppliers and providing economical feed ingredients for livestock growers. Little work has been conducted to evaluate the quality of hemp by-products for livestock production, although the increasing use of hemp by-products is expected as these markets grow. Hemp production is still relatively small scale, and the availability of by-products is inconsistent, thus many of these avenues are limited or have yet to be developed. However, nutrient analyses of hemp constituents (Table 1) suggest these by-products could find a range of uses. Similar to other plants, hemp nutrient concentrations and fiber digestibility vary depending on growing conditions, production management, and the plant portion tested (Albrecht et al. 1987; Tremblay et al. 2002). Crude protein (CP) in hemp by-products ranged from 5.3 to 24.5%, versus an average of 6.9% for the whole plant. Hemp NDF ranged from 27.9–84.4% for individual parts and 81.6% for whole plant NDF; by-products rich in leaf or flower components generally had relatively low NDF levels. However, energy concentrations calculated as TDN were relatively low compared to other forages (Kleinhenz et al. 2020). Thus, hemp by-products would generally be poor sources of energy in livestock diets but could be useful sources of dietary fiber (Kleinhenz et al. 2020). Spent biomass—particularly the residuals from cannabinoid extraction—may prove a better source of nutrients than hemp stalks, although they may have less value than more traditional feedstuffs. E.

Leaves 13.0 8.9 20.8 44.7 41.0

a

Stalk 5.3 1.2 64.6 84.4 19.8

a

Hempa flower 21.2 12.5 26.1 52.5 53.6

Seeda heads 23.0 13.2 29.6 53.2 61.5 Chaff 20.0 4.6 18.0 27.9 54.3

a

Extracteda flower 24.5 3.2 18.1 30.9 46.0

a

NR not reported (Kleinhenz et al. 2020); bSpent hemp biomass (SHB) (Ates 2021); c(Kim and Nyachoti 2017)

CP Fat ADF NDF TDN %

Wholea plant 6.9 2.7 60.8 81.6 24.0

Table 1 Nutrient concentration (% DM) of hemp plants and plant by-products Wholeb plant SHB 22.4 4.3 32.3 40.1 53.6

Stemsb & leaves SHB 19.2 7.5 17.6 23.4 69.9

Hempc hulls 21.9 23.5 37.9 57.1 NR

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g., spent hemp biomass from CBD production had protein content similar to alfalfa, but hemp had greater NDF concentrations and lower TDN, despite having greater levels of fat (Ates 2021). Hemp hulls from the dehulling process represent another potential hemp by-product that could be used in animal diets. Dehulling is intended to only remove the outer fibrous fraction of hemp grains but inevitably some endosperm is comingled with the hulls, increasing their protein and fat concentrations (House 2021). However, hulls may only be suitable at limited dietary inclusion levels, at least with monogastric species, as decreased energy values were observed for pigs fed hemp hulls added to a basal diet (Kim and Nyachoti 2017). Perhaps a bigger constraint on hemp as a by-product arises from the various hemp industries being in their infancy. Until significant markets arise that can take the fiber, flowers, and grains in substantial quantities—and generate substantial volumes of by-products—there likely will be little in the way of by- or co-product development with hemp. As well, much of the research surrounding hemp is focused on improving seed, fiber, and flower production, and developing best management practices for the crop in agricultural production systems. Such work is essential to support nascent hemp industries, but the use of hemp by-products in livestock feeding schemes will likely remain a secondary enterprise until these materials are more broadly available.

3.2

Hemp as a Dedicated Forage Crop

As an annual crop that actively grows when most cool-season forages slow, hemp may have potential as an alternative or emergency summer forage. Feeding the whole hemp plant, including leaves and stalks could be possible for ruminants and horses, or other species that can digest fiber. However, few data are available evaluating hemp’s value as a forage. Recently, Stringer (2018) evaluated hemp’s forage potential using laboratory estimates of nutritive value and digestibility. Hemp biomass was 17% CP 42 days after planting, which is comparable to cool-season grasses in the vegetative state (NRC 2007). Stringer (2018) concluded that variety and planting date influences hemp’s suitability as a forage but that yields were not adequate to make hemp an economical choice for farmers. The harvest method may be an important consideration for using hemp as a forage. For example, Pecenka et al. (2007) demonstrated that hemp (apparently harvested before grain formation) made suitable silage with a CP content of 24.8%. In an on-farm trial in Canada, hemp silage CP levels around 19% (comparable to alfalfa silage) but ADF concentration (41%) was much higher than the barley silage at (28%) produced on the farm. Although it could be assumed the digestibility and intake would be reduced, heifers anecdotally preferred the hemp silage to barley silage and did a better job cleaning up the feed bunk (Duckworth 2000). No production parameters were reported, however. Although empirical evidence indicates hemp can be grazed, as far as the authors are aware, no published studies exist that examine hemp (or animal) responses to

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grazing. In North America, extant feral hemp populations (with heritage in past fiber production systems) remain in the Midwest and Great Plains states. Animals have been observed to browse these hemp stands, particularly during times of summer drought, when hemp was greener than available forages (Vines, pers. comm.). Additionally, animal industries’ use of hemp has been constrained in part over regulatory issues. Concerns regarding cannabinoids being consumed and contaminating meat or milk has kept hemp from being used as a feed resource (EFSA 2011). Research is lacking regarding cannabinoid consumption in livestock and animal health as well as the safety of meat, dairy, and egg products intended for human consumption. Hemp’s suite of aromatic terpenes may present additional challenges to acceptance and palatability for livestock—and possibly their human end consumers. Sensory characteristics associated with smell can influence feed preferences in livestock (Rapisarda et al. 2012). Lambs exhibited various degrees of preference for spent hemp biomass—from uninhibited consumption to total refusal (Ates 2021). Feed processing methods such as pelleting or feeding in combination with other feedstuffs could increase acceptance depending on the intended species (Coffey et al. 2016). Kleinhenz (2021) noted similar concerns, commenting that steers picked around the hemp material and only increased intake with the addition of molasses to the ration. Although historical accounts of feeding hemp to livestock (Clarke and Diemenstraat 1995; Bamikole and Ikhatua 2009) and modern understanding of animal behavior suggests that animals would adapt, breeding (to reduce terpenes), processing (e.g., pelleting feed material or making as silage), and mixing with other feed materials (to dilute secondary plant metabolites) could be viable options to improve the utility of hemp and hemp products. Hemp’s use as a forage source also needs economic evaluation. To be profitable, the value of feeding hemp by-products to livestock would need to outweigh any additional costs incurred. Much work remains to determine the value of feeding hemp and hemp by-products to livestock, and without production and feeding trials the estimates of hemp utility as a forage remain a speculative effort.

4 Summary of Hemp Seed and Hemp Seed Byproducts Fed to Livestock Diets Current research suggests that hemp and hemp by-products may be a valuable source of protein, fat, and fiber for livestock diets and could increase the quality of composition of animal-based food products (e.g., meat, eggs, and milk). However, as of this writing, several countries have banned the use of hemp in commercial animal feed citing the inability to draw satisfactory safety conclusions based on the limited body of research available (Sandison 2017). Additional research is currently underway, but the process is lengthened by the need to evaluate not only whole seed but the various hemp-based products individually; moreover, safety demonstrations

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must be performed for both livestock and human consumers of those animal-derived food products. Empirical and historical observations, along with limited research literature, agree that hemp seed, oil, and seed cake have potential as suitable protein and fatty acid sources for many animal species, and whole plant, stalk, and leaves might be suitable as roughages for ruminants and horses. However, potential THC contamination of meat, milk, and eggs remains a concern and presents an entirely different obstacle to approval for use in production livestock diets—independent of approval based on the plant’s nutritional characteristics. The following is a summary of what we do know regarding hemp’s feeding value in livestock diets. Dietary enrichment to increase ω3 consumption is desired to decrease human ω6:ω3 fatty acid ratios. Supplementing livestock diets is generally accepted as the most efficient method of increasing fatty acid content in meat, milk, and eggs, although factors such as genetics, age, and gender also play a role in such responses (Woods and Fearon 2009). Much of the early research has focused on poultry meat and egg production. Hemp feeds have been incorporated into laying hen and broiler diets at inclusion rates up to 30% (hemp seed) and 12% (hemp seed oil) with no negative effects on hen or broiler performance (Silversides and Lefrançois 2005; Gakhar et al. 2012; Neijat et al. 2014). Flaxseed and fish oil also are both naturally high in ω3 and often used to increase dietary ω3, but consumers sometimes report altered sensory characteristics in eggs from chickens fed these diets (Konca et al. 2019). In contrast, to date no studies have reported significant differences in sensory characteristics of eggs from laying hens fed hemp seed (Goldberg et al. 2012; Konca et al. 2019). Many of these studies agree that including hemp seed products in animal diets improved the nutritional value of eggs and meat, resulting in greater ω3 content and lower ω6:ω3 ratios (Gakhar et al. 2012; Halle and Schöne 2013; Neijat et al. 2014; Mierliţă 2019; Skřivan et al. 2020). Although hemp does not contain DHA, the elevated ALA concentrations in hemp seed products can be converted to DHA in laying hens, resulting in increased concentrations in yolks. However, conversion of ALA to DHA appeared to be limited as ALA intake increased (Gakhar et al. 2012). Interestingly, studies comparing hemp seed to hemp seed cake and oil have shown whole hemp seed to be more effective at increasing egg weights (Gakhar et al. 2012; Mierliţă 2019). Dairy cattle tolerate up to 14% hemp seed cake in the diet with resulting increased milk yields; however, decreased yield was observed at greater levels of dietary inclusion (Karlsson et al. 2010). Voluntary intake was not affected in sheep supplemented with up to 20% hemp seed cake (Mustafa et al. 1999) and dairy goats had no adverse effects in response to 9.3% hemp seed and 4.7% hemp seed oil in the diet (Cozma et al. 2015; Cremonesi et al. 2018). For these goats, neither treatment affected milk yield, but milk fat concentration was greater when either hemp seed or seed oil was fed; however, only hemp seed oil treatments increased milk protein content possibly because the nutritional profile was less limiting than the control diet (Cozma et al. 2015; Cremonesi et al. 2018). Hemp feeding increased the PUFA content in ewes’ milk and increased both the ω3:ω6 ratio and the

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α-tocopherol content, with the latter effect leading to an increase in antioxidant activity (Mierliţă 2018). Dry matter intake, average daily gain (ADG), and feed efficiency were not affected by feeding hemp seed to cattle, however, ω3 fatty acids in tissues were increased (Gibb et al. 2005). Growing calves fed hemp seed cake had greater feed intake but similar live weight gains to calves fed soybean meal, resulting in lower feed efficiency (Hessle et al. 2008). Lambs fed barley diets supplemented with hemp seed cake had similar intake but lower gain and feed conversion than lambs supplemented with peas or rapeseed cake (Karlsson and Martinsson 2011). This may reflect low energy content due to high NDF in the diet supplemented with hemp seed (Karlsson and Martinsson 2011). Besides evaluating the palatability of feeding hemp silage and spent hemp biomass, scant published literature is available that evaluates hemp’s potential as a forage. Costs relative to productivity (and the establishment and production challenges) may render this a specialty crop at best for at least the near term. Hemp seed is generally well-tolerated in livestock diets; however, much remains to be answered about the suitability and efficacy of supplementing livestock diets with hemp.

5 Conclusions Hemp has a long history of use as a livestock feed source, although scientific investigation is just beginning. Hemp seed and by-products offer potential value as feeds or supplements in livestock diets, particularly for increasing targeted fatty acid and amino acid intake to enhance nutrient profiles of meat, milk, and eggs. Although promising, understanding of the functional properties of hemp is limited, and further work is needed to evaluate plant chemical composition and nutrient interactions and to establish safe intake recommendations. Further work also needs to be done to evaluate cannabinoid transfer to livestock-based food products. (Indeed, one producer we know has asked if this could be a “value-added” selling point.) Likewise, agronomic studies are needed to identify suitable cultivars, planting densities, and responses to defoliation. Areas of focus include selective breeding to improve the nutritional quality of hemp seed by increasing fatty acids (ALA and GLA) and amino acid lysine. Furthermore, production systems must be developed to provide a consistent, economical product. Current industry practices for commodity meat, milk, and egg production typically involve feeding least-cost diets. If hemp is to be competitive as a commodity feed resource, it must offer equal (or lower) cost for value relative to existing commodity feedstuffs. Alternatively, producers must be able to capture the “value add” from the greater quality (and higher cost) animal products produced with hemp feeds. Hemp faces the further challenge of meeting regulatory requirements for levels of cannabinoids in animal products. Standardized production practices would increase unity between the industrial hemp and livestock sectors. Arguably, demand for hemp in the human sector has already increased the availability and

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curiosity of hemp by-product use in the livestock sector. While the use of hemp is promising, much remains to be determined about the safety and suitability when fed to livestock.

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Biotechnological Transformation of Hempseed in the Food Industry Barbara Farinon, Romina Molinari, Lara Costantini, and Nicolò Merendino

Abstract Industrial hemp is a multi-purpose crop that has been reintroduced from the 90s after chemical and genetic differentiation between narcotic and non-narcotic strains. This has encouraged the interest of many researchers, including those in the food industry sector. Hempseeds represent an important and nutritionally valuable resource due to their macro- and micro-nutrients and phytochemical composition. Hempseed production is increasing rapidly in many parts of the world, together with the development of alternative hempseed-based daily foods or processed hempseeds-derived products, including hempseed oil, meal, flour, and protein isolate/hydrolysate. Due to the relatively recent renewal of hemp production, the agrofood industries still lack standardized and specific transformation technologies and processing methods for hempseeds, thus prompting scientific research around this topic. Hence, current literature concerning the biotechnological transformation used on hempseeds and their derivatives has been reviewed in this chapter. Overall, many biotechnological methods can be effectively applied on whole hempseeds, hempseed oil, meal, flour, bran, and protein isolate/hydrolysate to valorize, improve, and use them differently in food preparation. To date, the most proposed, assessed, and adopted relevant biotechnological protocols aim to improve the bioavailability and functionality of nutrients and phytochemicals in hempseeds and derivatives. Also, these protocols focus on reducing harmful anti-nutrients and improve consumer acceptability of the final product. Techniques used to achieve these objectives include enzymatic hydrolysis, fermentation, roasting, extrusion, extractions through supercritical fluid, microwave, and ultrasound, and microencapsulation. Despite the advances in knowledge made so far, there are still gaps in hempseed’s transformation processes; thus, further investigations are needed to optimize them specifically. Keywords Cannabis · Hemp · Food processing · Hempseed bran · Hempseed meal · Hempseed oil · Hempseed proteins · Whole hempseed

B. Farinon (*) · R. Molinari · L. Costantini · N. Merendino Department of Ecological and Biological Sciences (DEB), Tuscia University, Viterbo, Italy e-mail: [email protected]; [email protected]; [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 D. C. Agrawal et al. (eds.), Cannabis/Hemp for Sustainable Agriculture and Materials, https://doi.org/10.1007/978-981-16-8778-5_7

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Abbreviations ALA AU BHT DW EFAs FTIR GLA HDL HPI IL-1β IL-6 LA LAB LAPU LPS MPa PUFAs Rpm SPI THC TNF-α

α-Linolenic Alcalase units 2.6-Di-tert-butyl-p-cresol Dry weight Essential fatty acids Fourier transform infrared γ-Linolenic acid High density lipoprotein Hempseed Protein Isolate Interleukin 2 Interleukin 6 Linoleic acid Lactic acid bacteria Leucine amino peptidase units Lipopolysaccharides MegaPascal Polyunsaturated fatty acids Revolutions per minute Soy protein isolate Δ9-tetrahydrocannabinol Tumor necrosis factor alfa

1 Introduction Hemp (Cannabis sativa L.) is an herbaceous annual plant belonging to the Cannabaceae family. This plant species include both intoxicant and non-dangerous varieties. The former is popularly named “drug-type” hemp because it contains a harmful level of one psychoactive compound, namely Δ9-tetrahydrocannabinol (THC), and their cultivation is restricted in most Western countries. In contrast, other varieties have a safer level of the same compound (