Technologies for Biochemical Conversion of Biomass Hongzhang Chen Professor at the Institute of Process Engineering Chinese Academy of Sciences, Beijing, China Lan Wang Professor at the Institute of Process Engineering Chinese Academy of Sciences, Beijing, China Academic Press is an imprint of Elsevier 125 London Wall, London EC2Y 5AS, United Kingdom 525 B Street, Suite 1800, San Diego, CA 92101-4495, United States 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom © 2017 Metallurgical Industry Press. Published by Elsevier Inc. No part of this publication may be reproduced or transmitted in any form or by any means, elec- tronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. 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Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-12-802417-1 For information on all Academic Press publications visit our website at https://www.elsevier.com/ Publisher: Jonathan Simpson Acquisition Editor: Simon Tian Editorial Project Manager: Naomi Robertson Production Project Manager: Julie-Ann Stansfield Designer: Greg Harris Typeset by Thomson Digital Preface Today, mankind is moving from a civilization based on industry to one which recognizes the importance of the ecosystem. To realize sustainable develop- ment, it is a prerequisite to find a clean substitute for the oil resources. Biomass, the solar energy stored in chemical form in plant, has attracted both industrial and academic interest as a promising clean and renewable resource. Biomass conversion technology owns significant advantages over other con- version technologies for being environment friendly, effectively, and operation condition moderately. Therefore, it attracts more attentions in comparison to the physical and chemical conversion technologies. Over the past 20 years, the author has been devoted to the study of biomass conversion and product devel- opment. And, luckily, breakthroughs were made in the setup of a steam explo- sion–based pretreatment platform, solid-phased–enzyme–fermentation–separa- tion coupling platform, and large-scale-solid-phased pure cultivation platform. All those platforms have been applied in industrialization productions and have received extensive acceptance from colleagues and enterprises. In the process of research and application, we proposed the notion of biomass biochemical conversion technology platform, which not only guided engineers to realize the biochemical conversion of biomass, but was also devoted to the development of related disciplines. With the development of research on biomass, related works have been pub- lished continuously. However, most of them focus on specified techniques for oriented biomass conversion, but only a few have provided a systematic and comprehensive review on the techniques employed. The author has summarized the existing research routes and results for the construction of biomass conver- sion platforms. It is expected to promote the conversion and use of biomass resources. The first two chapters review the unit operations of biomass conversion. Chapters 3–8 discuss conversion platforms: pretreatment platform, enzyme platform, cell refinery platform, sugar platform, fermentation platform, and posttreatment platform. Chapter 9 discusses polygeneration of the bioconver- sion products. The research on biomass biochemical conversion was supported by the National Key Basic Research Development Program of China (973 project, Nos 2004CB719700 and 2011CB707400) and the National High Technol- ogy Research and Development Program (863 Program, 2012AA021302). In xi xii Preface addition, the works of my coworkers and students were essential precondi- tions for completing this book. Dr. Menglei Xia, Dr. Zhimin Zhao, Dr. Zhihua Liu, Master Lanzhi Qin, Master Meixue Shao, Dr. Guanhua Wang, Dr. Wenjie Sui, Dr. Yuzhen Zhang, Dr. Guanhua Li, Master Yingyi Duan, Dr. Litong Ma, Dr. Zhiguo Zhang, Dr. Qin He, and Dr. Ning Wang participated in writing this book. Dr. Lan Wang participated in the revision and review of the book. Many references of our predecessors and colleagues have been cited in the book. I wish to express my sincere thanks to all of them. Some errors may exist in this book. I sincerely hope to receive criticism and guidance from readers in this regard. Hongzhang Chen State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences St. Zhongguancun, Beijing, Peoples’s Republic of China June, 2015 Chapter 1 Introduction Chapter Outline 1.1 The Concept of Biomass 1 1.3 Role and Status of Biochemical 1.2 Biomass Conversion Methods 2 Conversion Technologies 1.2.1 Biomass Physical of Biomass 5 Conversion 1.4 Overview of Biochemical Technologies 2 Conversion Platform 1.2.2 Biomass Chemical of Biomass 7 Conversion 1.5 Prospects of Biochemical Technologies 3 Conversion of Biomass 1.2.3 Biomass Biochemical Industry 8 Conversion References 9 Technologies 5 1.1 THE CONCEPT OF BIOMASS Biomass is a solar energy resource that has been utilized by humans for a long time. Solar energy is saved in the form of chemical energy through plant pho- tosynthesis, and thus things like oxygen for breathing, plants and animals for food, wood for building and making fire, and clothes for cover and warmth appeared. However, it has been only 50 years since biomass was truly defined by humans. Biomass in English was first used in 1934 (it was defined as living weight in Merriam-Webster). According to the foreign retrospective database, biomass was defined as what it is nowadays in the Journal of Plant and Soil of America (Tergas & Popenoe, 1971). In 1976, four years after the 1972 oil crisis, an article (Tergas & Popenoe, 1971) introducing biochemical engineering proposed that wasted biomass could be reused as a kind of raw material. In 1979, an article (Crutzen, Heidt, & Krasnec, 1979) in Nature pointed out that the combustion of biomass produced polluted gases, while in 1980, the college of Process Engi- neering of Agriculture at the University of Netherlands indicated that biomass could be regarded as the source of energy materials (Bruin, 1980). In 1981, Oak Ridge National Laboratory of America started the security assessment of biomass energy technologies (Watson & Etnier, 1981). Since then, reports Technologies for Biochemical Conversion of Biomass © 2017 Metallurgical Industry Press. Published by Elsevier Inc. 1 2 Technologies for Biochemical Conversion of Biomass and research about biomass energy have come to the stage (Mes-Hartree & Saddler, 1983; Miller & Fellows, 1981; Schwarzenbach & Hegetschweiler, 1982; Stout, 1982; Zadražil & Brunnert, 1982; HongZhang & ZuoHu, 2000; Chen & Qiu, 2010). If we set the year 1980 as the origin of biomass utilization research, it has been over 30 years since then, which is also the time that a child takes to pay back to his or her family and society from birth. Within this time, biochemical conversion technology of biomass has developed rapidly, similar to the payback to family and society by the grown-up child. Research into biochemical conver- sion technology of biomass also began its journey to industrial application. The definition of biomass according to the US Department of Energy includes any animal and plant organisms. In particular, biomass in the USA includes agriculture and forestry waste, municipal solid waste, industry waste, and terrestrial and aquatic crops. The definition of biomass according to China’s Renewable Energy Associa- tion covers all kinds of organisms formed through plant photosynthesis, includ- ing all animals, plants, and microorganisms. Plants are autotrophs (producers), while animals are heterotrophic organ- isms (consumers). Humans selected those animals and plants for their own ben- efit during their survival process, and used animals the most. Regarding plants, humans used fruits that are rich in starch, protein, fat, and vitamins. Humans did not look for ways to use the other parts of plants, as there was no urgent need to do so. The biomass mentioned in this book refers to the lignocellulosic waste of plants besides those used for food and medicine. 1.2 BIOMASS CONVERSION METHODS Lignocelluloses are mainly composed of cell walls of dead cells. The main components of cell walls are cellulose, hemicellulose, and lignin, while pectin is the main component of the intercellular layer. Hemicellulose and lignin are connected to each other by chemical bonds, and the three components are con- nected by hydrogen bonds, resulting in the tight cell walls based on the skeleton formed by multistage fiber structure. In order to utilize lignocellulosic materi- als, the first step is to destroy the existing cell walls. There are various utilization technologies of biomass, but they can come down to three overall categories: physical conversion technologies, chemical conversion technologies, and biochemical conversion technologies. 1.2.1 Biomass Physical Conversion Technologies Biomass physical conversion technologies refer to the modification and pro- cessing of biomass to produce high-value products, thus realizing the value- added utilization of lignocellulosic materials. The main products of physical conversion technologies include sheets, construction materials, and lignocel- lulosic composites. Introduction Chapter | 1 3 The technology of biomass artificial sheets includes preparation of raw materials, mixing, molding, and posttreatment (Duan, He, & Shang, 2009). Nontimber lignocellulosic materials that are fit for biomass artificial sheets include bagasse, wheat straw, straw, corncob, cotton stalk, and shive. Bio- mass artificial sheets, especially the nontimber lignocellulosic biomass artifi- cial sheets, have positive significance for reducing the consumption of forest resources and protecting the environment. Biomass construction materials include biomass wall materials (Cui, Cui, & Bao, 2006), of which light straw magnesia cement springboard (Zhang, Liu, & Xun[J], 2011) and straw board (Zhu, Wang, & Liu, 2010) are the main categories; there are also others, such as corn straw insulation materials (Ding, Ren, & Zheng, 2014). The process- ing of these wall materials is similar to that of lignocellulosic boards, and thus the wall materials have properties of lightness, sound insulation, earth- quake resistance, and anticorrosiveness. Artificial boards and wall materials are rudimentary forms of lignocellulosic materials usage. At present, humans utilize lignocelluloses for processing directly, while the manufacture of artifi- cial board, using cellulose extracted from lignocellulosic materials, has fewer application examples. Woody biomasses are mostly used to produce biomass composites (Li, 2008). There are three forms of woody materials: laminated composite, hybrid composite, and penetration composite. Laminated composite is formed by glue lamination and pressurized glue of certain shaped sheets; it has a lay- ered structure and a certain size and shape. Hybrid composite is obtained from the mixing of wood or woody materials as the base with other materials, such as inorganic materials and minerals, or the mixing within lignocellulosic materi- als; this is then pressurized into boards. Penetration composite is made by fil- tering a substance (inorganic materials, organic materials, and metal elements) into wood or woody materials, and then using deposition or chemical reaction to improve wood properties or give wood a certain function. Therefore, we can see that the physical conversion of plants mainly uses their tight physical structure and then converts them into materials. The prod- ucts are utilized in daily life and production. However, physical conversion can hardly convert biomass into renewable products that could displace petroleum products, thus such technology cannot satisfy the needs of clean energy and chemicals nowadays. 1.2.2 Biomass Chemical Conversion Technologies Biomass chemical conversion technologies used to be applied in the pulp and paper industry. As the problems of energy and environment arise, people pay much attention to the research and application of biomass. There are many biomass chemical conversion technologies, including combustion, carbon- ation, gasification, thermal decomposition, and hydrothermal liquefaction technology. 4 Technologies for Biochemical Conversion of Biomass The traditional paper industry mainly adopted an acid-based chemical pre- treatment approach to obtain cellulose in biomass for pulp preparation. However, due to the irreplaceability of paper production, we will not discuss the item here. Combustion of chemical conversion technologies is carried out to utilize the intense heat released during oxidation directly or convert it to power. Hemicel- lulose can be decomposed severely below 300°C. Cellulose can complete the decomposition process among 300–350°C. When the temperature exceeds 500°C, lignin begins to decompose. Such technology has a long history and is relatively cost-efficient. However, it generates a lot of greenhouse gases, such as SO 2. Carbonation of chemical conversion technologies, a sort of ancient technol- ogy of biomass conversion, is to heat biomass to obtain gas, liquid, and solid products under air-free or air-limited conditions. Mechanism charcoal (Gao, Ma, & Shen, 2010) is also called artificial carbon or molding charcoal; this is molded under high temperature and high pressure, and then pyrolysis car- bonized to get solid carbon products. By-products like tar and crude vinegar are obtained by condensation, recycling, and processing the gas mixture that is generated from pyrolysis. Tar, containing a high degree phenolic substance and many organic substances, is a raw material from which to extract aromatic compounds. Tar can also reconcile with the residue to produce No. 200 high- grade gasoline, or mix with coal as a coal-fired boiler fuel. Crude vinegar is not only a kind of chemical raw material, can also be used to help produce antimil- dew agents, insect-resistant agents, and antibacterial agents; in addition, it could increase efficiency when used with pesticides and reduce pesticide residues. Gasification of chemical conversion technologies (Shi & Hua, 2007) is car- ried out to convert the combustible parts of biomass into flammable gas (mainly hydrogen, carbon monoxide, and methane) at a high temperature using oxygen or oxygenates in the air as gasification agents, due to the properties of high vola- tile components, high carbon activity, and low sulfur and ash of biomass. It was proposed primarily by Ghaly to produce fuel gas of low density. According to its application, gasification can be divided into pressure gasification and gasifica- tion, whose principles are the same, while the latter has higher requirements for equipment, operations, and maintenance. Thermal decomposition technology is decomposes biomass materials into at least two components. Rapid thermal decomposition refers to the process of increasing the heating rate during thermal decomposition of raw materials, leading to instantaneous thermal decomposition at several hundred degrees Celsius. Thermal decomposition fluid, wood vinegar, quick carbide, and anhy- drosugar are produced by thermal decomposition of biomass. Thermal decom- position fluid and quick carbide can be used in fuels. Wood vinegar can be used in smoked liquid, exterminator, and pesticide substitutes. Anhydrosugar can be used in polymer materials to produce biodegradable plastics. Hydrothermal liquefaction technology decomposes biomass in water at a high temperature and pressure. Similar to thermal decomposition technology, gas, liquid, and solid products can be obtained through hydrothermal liquefaction. Introduction Chapter | 1 5 The light component in the liquid phase (wood vinegar) dissolves in water, while heavy components mix with solid phase; thus three types of mixture were obtained gaseous, aqueous, and oleic (a mixture of oil and carbon). It is concluded that biomass chemical conversion technologies require rel- atively fierce conditions. Except for power generation, the products obtained have lower purity and cannot replace oil products as fine chemicals; nor can they be used as universal raw materials for industry to meet the demand of energy and environment. 1.2.3 Biomass Biochemical Conversion Technologies Biomass biochemical conversion technologies refer to the conversion of bio- mass into corresponding products through certain physical, chemical, and biological pretreatments. Pretreatments in the biochemical conversion technolo- gies of biomass aim to help reach ideal conversion effects, not to produce final products, which is the essential difference between the aforementioned physical and chemical conversion of biomass. In addition, biochemical conversion tech- nologies of biomass are more moderate than the other two. Biomass can be turned into different products, such as hydrogen, biogas, ethanol, acetone, butanol, organic acids (pyruvate, lactate, oxalic acid, levulinic acid, citric acid), 2,3-butanediol, 1,4-butanediol, isobutanol, xylitol, mannitol, and xanthan gum by selecting different microorganisms in the process of bio- chemical conversion (Chen, 2010). On the one hand, such products can synthe- tize replacements of petroleum-based products. On the other hand, the products can replace products derived from grains, such as ethanol. Compared with other conversion technologies, biomass biochemical conver- sion technologies are moderate, pure, clean, and efficient. Moreover, biomass can be turned into various intermediates by screening different enzymes or microorganisms through biochemical conversion technologies, thus providing many platform substances for the conversion of renewable materials, fuels, and chemicals. As a result, people pay much attention to biochemical conversion technologies of biomass. 1.3 ROLE AND STATUS OF BIOCHEMICAL CONVERSION TECHNOLOGIES OF BIOMASS We can see that through such a moderate way as biochemical conversion technologies of biomass, replacements of petroleum-based products can be obtained, which is potentially a new model to develop ecological agriculture so as to realize a circular economy. It will play an important role in solving energy, environment, and rural issues. Hence, biochemical conversion technologies of biomass are important to long-term development and society stability. The role and status of biochemical conversion technologies of biomass are reflected in the following aspects. 6 Technologies for Biochemical Conversion of Biomass 1. It is the base of human living. Since oil was discovered and first exploited and used by humans, oil-based products have played an important role in many aspects of human life and production, especially the role of energy during production. However, according to BP statistics in 2010, oil can only be exploited for 45.7 years, natural gas for 62.8 years, and coal for 119 years. The world energy prospects of BP for 2030 indicate that the consumption of liquid fuel will increase from 39.433 Gt in 2010 to 46.711 Gt in 2030, while the yield of biofuel will increase from 575 Mt in 2010 to 2351 Mt in 2030. Meanwhile, compared with grains, lignocelluloses are cheaper and richer on earth than the raw materials used to produce biofuel. Therefore, it is important in terms of the survival of humans to turn biomass of lignocel- luloses, especially agriculture and forestry waste, into raw materials that can substitute for petroleum. 2. It is an important way to make humans live in harmony with nature. In the long-term history of humans’ development, although they created an indus- trial civilization at the cost of cheap oil, coal, and natural gas as their capital, humans have caused a series of problems like the greenhouse effect and human health problems due to environmental pollution because of their ignorance of the carrying capacity of the earth. If we want to turn such a development pattern around, especially in terms of reducing our industrial system’s dependence on oil, an important way is to develop a new industrial chain that could replace petroleum-based products. Biochemical conversion technologies of biomass have been applied in the industrial system because we can get biobased energy, materials, and chemicals that can replace petroleum-based products through these technologies. Biochemical conver- sion technologies of biomass are clean and their materials are renewable biomass. The development of biobased products brings the intermediate products of ecological cycle to serve humans using the process of ecological transformation in nature; thus it is an important way to make humans live in harmony with nature. 3. It is an essential method to change the role of agriculture and increase farm- ers’ income. Agriculture has played the role of food supplier in society. Agriculture cannot pay for education, health care, and other fundamental needs (e.g., marriage expenses and pensions) in farmers’ lives any more, although the production of grains suffered little effect of natural disasters or the price of grains are protected by the government. Consequently, produc- ing biobased products, which adds new roles of farm products as energy and materials through biomass by biochemical conversion technologies of biomass, can increase farmers’ income in two aspects. The first aspect is that the agriculture and forestry waste, which used to abandoned, can be sold as products to increase farmers’ income; the other aspect is the rise of new industries of biochemical conversion technologies of biomass, especially the ever-rising private enterprises, which increase employment opportunities for farmers, thus increasing farmers’ nonfarm income.