Biohydrogen Production and Hybrid Process Development: Energy and Resource Recovery from Food Waste

By Zhao Youcai and Zhou Tao

Biohydrogen Production and Hybrid Process Development: Energy and Resource Recovery from Food Waste explores the production of biohydrogen from food waste via anaerobic fermentation, focusing on effect factors, control methods and optimization. The book introduces food waste treatment and disposal technologies, including operational principles and process control. The authors discuss the use of aged refuse, the effect of several key factors on anaerobic gas production rate, process parameters optimization for enhancing biohydrogen yield, key factors in biohydrogen production from sewage sludge fermentation, and new developments in nutrition recovery from food waste.

This book spans the entire production cycle, from waste recovery to its conversion processes, end-product, and by-product utilization, providing engineering researchers, PhD students, and industry practitioners in the field of biohydrogen production, biogas production, biomass conversion, and food waste management with a thorough background on the production of hydrogen via anaerobic fermentation.

• Covers the fundamentals and applications of the use of food waste for biohydrogen production through anaerobic digestion
• Explores core challenges of biohydrogen production operations, including details on process optimization and control, and multiple case studies grounded in current industrial practice
• Includes methodological perspectives comparing and contrasting approaches to biohydrogen production using anaerobic digestion with optimization techniques for production efficiency

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 7, 2020
• ISBN: 9780128232507

Zhao Youcai

Zhao Youcai, is currently a professor of environmental engineering at School of Environmental Science and Engineering, Tongji University. He got bachelor degree from Sichuan University (1984) and Ph.D. from Institute of Chemical Metallurgy (now Institute of Process Engineering), Chinese Academy of Sciences, Beijing (1989). After finished Post-doctoral research work at Fudan University, Shanghai, he joined in Tongji University in 1991. Meanwhile, he had ever worked at Aristotle University, Greece, National University of Singapore, Tulane University, USA, and Paul Scherrer Institute, Switzerland, for 4 years as research fellow or visiting professor. He had authored or co-authored 200 publications published in peer-reviewed internationally recognized journals, 480 publications in China journals, authored 9 English books (at Elsevier and Springer) and authored or co-authored 98 Chinese books (as an author or Editor-in-chief), 4 textbooks for undergraduate, graduate and PhD students with a fourth edition of undergraduate textbook (in Chinese). Currently, his research interests include treatment and recycling of municipal and rural solid waste, construction and demolition waste, hazardous waste, industrial waste, electric and electronic waste, and sewage sludge, and polluted soil.

Book preview

Biohydrogen Production and Hybrid Process Development

Energy and Resource Recovery from Food Waste

Zhao Youcai

Environmental Engineering, College of Environmental Science and Engineering, Tongji University, Shanghai, P.R. China

Zhou Tao

Environmental Engineering, College of Environmental Science and Engineering, Tongji University, Shanghai, P.R. China

Table of Contents

Cover image

Title page

Copyright

List of contributors

About the authors

Preface

Summary

Abbreviations

Chapter 1. Anaerobic fermentation process for biohydrogen production from food waste

Abstract

1.1 Food waste sources

1.2 Food waste characteristics

1.3 Food waste generation/yield and prediction models

1.4 Treatment and disposal methods of food waste

1.5 Principle and process progress of biohydrogen production

1.6 Anaerobic fermentation biohydrogen production system

1.7 Environmental influence factors of anaerobic fermentation biohydrogen production

1.8 Operation parameters’ regulation of biohydrogen production

Chapter 2. Optimization of biohydrogen production with additives and inoculum from food waste

Abstract

2.1 Biohydrogen production via inoculation sludge and pretreatment

2.2 Metal ion effect on biohydrogen production

2.3 Synergistic effect of aged refuse and laundry detergent on biohydrogen production

2.4 Optimization of biohydrogen production with compound alkaline

2.5 Acidification pretreatment for biohydrogen production enhancement

2.6 Fe and nitrogen source addition on biohydrogen production from food waste

2.7 Inoculated microorganisms and PCR–DGGE analysis

2.8 Anionic surfactant addition on biohydrogen production

Chapter 3. Pretreatment and aged refuse dosage on biohydrogen production from food waste

Abstract

3.1 Biohydrogen production in food waste–sludge composite

3.2 Optimization of satisfaction function

3.3 Quality evaluation of the biohydrogen production process model

3.4 Thermal hydrolysis on properties of food waste

3.5 Thermal hydrolysis on biohydrogen production

3.6 Initial pH values on biohydrogen production

3.7 Acid production from food waste anaerobic fermentation

3.8 Static anaerobic fermentation

3.9 Continuous anaerobic fermentation biogas production

3.10 Design and operation of a pilot system

3.11 Enhanced biohydrogen production with aged refuse addition

Chapter 4. Simultaneous anaerobic fermentation biohydrogen and biomethane production from food waste

Abstract

4.1 One-component organic matter biohydrogen production fermentation

4.2 Food waste fermentation for hydrogen production

4.3 Methane fermentation from biohydrogen fermentation residue

4.4 Development and commissioning of integrated hydrogen production and methane production equipment

4.5 Combined biohydrogen production and methane production process on-site

4.6 Design and operation management of a biohydrogen and biomethane production treatment plant for food waste

Chapter 5. Combined anaerobic fermentation biohydrogen and biomethane production for sewage sludge and food waste

Abstract

5.1 Pretreatment for biohydrogen production from sewage sludge anaerobic fermentation

5.2 Inhibitors of sludge anaerobic fermentation biohydrogen production

5.3 Leachate additives for enhancing biohydrogen production from sludge

5.4 Fresh food waste addition in biohydrogen production from sludge

5.5 Combined anaerobic fermentation of heat-treated sludge and acidified food waste

5.6 Mechanism of combined anaerobic fermentation of food waste and sludge

5.7 Combined anaerobic fermentation from heat-treated sludge and acidified food waste

5.8 Response surface optimization for heat-treated sludge and acidified food waste anaerobic fermentation

Chapter 6. Design and optimization of a biohydrogen production reactor

Abstract

6.1 Design of a semicontinuous anaerobic rotary drum

6.2 Overall structure and working principles of a semicontinuous anaerobic rotary drum

6.3 Structural parameters

6.4 Design of a conventional reactor

6.5 Semicontinuous fermentation process based on a semicontinuous anaerobic rotary drum

6.6 Comparison with conventional continuous stirred tank reactors

6.7 Environmental benefits of anaerobic fermentation from food waste

Chapter 7. New developments in nutrition recovery from food waste

Abstract

7.1 Synthesis of composite hydrogel fertilizers from food waste

7.2 Remediation of contaminated soil with composite hydrogel fertilizers

7.3 Efficient capture of aqueous humic acid using a functionalized stereoscopic porous activated carbon based on poly(acrylic acid)/food-waste hydrogel

Bibliography

Index

Copyright

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List of contributors

Zhao Aihua,     Shanghai Chengtou Group Company Ltd., Shanghai, P.R. China

Liu Changqing,     Tongji University, Shanghai, China and Fujian Normal University, Fujiang, P.R. China

Niu Dongjie,     Tongji University, Shanghai, P.R. China

Qin Feng,     Shanghai Shang Shi Environment Company Ltd., Shanghai, P.R. China

Chai Fuliang,     Chongqing Environmental Sanitation Engineering Group, Chongqing, P.R. China

Jiao Gangzhen,     Tongji University, Shanghai, P.R. China

Zhou Haiyan,     Shanghai Laogang Waste Disposal Company Ltd., Shanghai, P.R. China

Tai Jun,     Shanghai Design Institute of Environmental Sanitation Engineering, Shanghai, P.R. China

Song Lijie,     Shanghai Design Institute of Environmental Sanitation Engineering, Shanghai, P.R. China

Zhang Meilan,     Shanghai Laogang Waste Disposal Company Ltd., Shanghai, P.R. China

Li Ming,     Tongji University, Shanghai, P.R. China

Wu Na,     Tongji University, Shanghai, P.R. China

Kuang Qian,     Chongqing Environmental Sanitation Engineering Group, Chongqing, P.R. China

Guo Qiang,     Tongji University, Shanghai, P.R. China

Wei Ran,     Tongji University, Shanghai, P.R. China

Huang Renhua,     Shanghai Chengtou Environment Company Ltd., Shanghai, P.R. China

Zhang Ruina,     Shanghai Design Institute of Environmental Sanitation Engineering, Shanghai, P.R. China

Chen Shanping,     Shanghai Design Institute of Environmental Sanitation Engineering, Shanghai, P.R. China

Dai Shijin,     Tongji University, Shanghai, P.R. China

Lin Shucan,     Shanghai Laogang Waste Disposal Company Ltd., Shanghai, P.R. China

Wu Shuya,     Tongji University, Shanghai, P.R. China

Zhou Tao,     Tongji University, Shanghai, P.R. China

Li Tian,     Tongji University, Shanghai, P.R. China

Geng Xiaomeng,     Tongji University, Shanghai, P.R. China

Qian Xiaoqing,     Tongji University, Shanghai, China and Yangzhou University, Jiangsu, P.R. China

Wang Xing,     Shanghai Design Institute of Environmental Sanitation Engineering, Shanghai, P.R. China

Zhang Xingqing,     Chongqing Environmental Sanitation Engineering Group, Chongqing, P.R. China

Wang Yan,     Tongji University, Shanghai, P.R. China

Guo Yanyan,     Tongji University, Shanghai, P.R. China

Yu Yi,     Shanghai Design Institute of Environmental Sanitation Engineering, Shanghai, P.R. China

Zheng Yilin,     Tongji University, Shanghai, P.R. China

Zhao Youcai,     Tongji University, Shanghai, P.R. China

Chen Yu,     Tongji University, Shanghai, P.R. China

Wang Zhengyu,     Tongji University, Shanghai, P.R. China

Zhu Zihan,     Tongji University, Shanghai, P.R. China

About the authors

Zhao Youcai

Zhao Youcai is a professor of environmental engineering at the School of Environmental Science and Engineering, Tongji University, China. He received his bachelor degree from Sichuan University (1984) and PhD from the Institute of Chemical Metallurgy (now Institute of Process Engineering), Chinese Academy of Sciences, Beijing (1989). After finishing postdoctoral research work at Fudan University, Shanghai, he joined Tongji University in 1991. He has worked at Aristotle University, Greece; National University of Singapore, Singapore; Tulane University, United States; and Paul Scherrer Institute, Switzerland, for 4 years as a research fellow or visiting professor. He has authored or coauthored 158 publications in peer-reviewed internationally recognized journals, 420 publications in Chinese journals, 85 books in Chinese, and six books in English (at Elsevier and Springer). His research interests include the treatment of municipal solid wastes, sewage and industrial sludge, hazardous wastes, polluted construction wastes, and industrial wastes.

Zhou Tao

Zhou Tao is an assistant research fellow of environmental engineering at the School of Environmental Science and Engineering, Tongji University, China. He received his bachelor degree in environmental engineering from Guangxi University China, and his PhD from Tongji University, China. He has authored or coauthored 10 peer-reviewed international papers, five Chinese papers, and four invited book chapters. His principal research interests lie in the treatment and resource recovery of food waste and landfill leachate, as well as odor pollution control.

Preface

Food waste is produced as a result of food processing by the general population, the food and beverage industry, and canteens/food retailers. The ingredients of food waste include rice, flour, grain, vegetables, vegetable oil, animal oil, meat and bone, both cooked and uncooked, and a small amount of waste utensils, toothpicks, and paper. Its chemical composition includes starch, cellulose, protein, lipids, and inorganic salts and also a small amount of nitrogen, phosphorus, potassium, calcium, sodium, magnesium, iron, and other trace elements. Hence, food waste is a solid–liquid mixture, and quite viscous, with complex chemical composition and components that may change depending on the location, climate, and even from day to day. Meanwhile, food waste is rich in organic matter and biodegradable components and thus provides a good environment for the growth and reproduction of a variety of pathogenic microorganisms and flies that may carry pathogens, which can result in the spread of diseases and have an adverse environmental impact on the public.

Leachate is generated by food waste in the presence of microorganisms, resulting in the release of odors and pollution of water and air. Improper methods of disposal may affect human health, the appearance of the locality, and environmental sanitation. Hence, it is necessary to explore effective methods of food waste disposal to protect the environment effectively. At present the most commonly used engineering technologies in food waste treatment include incineration, sanitary landfill, anaerobic digestion, aerobic composting, and earthworm composting.

It is generally thought that anaerobic fermentation comprises three stages: hydrolysis and fermentation, production of hydrogen and acetic acid, and the resulting production of methane. Biohydrogen production is generally divided into three methods: photosynthetic biological hydrogen production, anaerobic dark fermentation hydrogen production, and a combination of these two methods. Compared with photo-hydrogen production, anaerobic fermentation of hydrogen is not limited by solar energy, and the rate of hydrogen production is higher. From the viewpoint of energy conversion, the free energy obtained by hydrogen production from fermentation is greater than that of photosynthetic hydrogen production. The hydrogen production reaction catalyzed by hydrogen enzymes does not require adenosine triphosphate, and therefore it is more favorable for hydrogen production.

In this book a comprehensive description of the technical aspects of biohydrogen production and hybrid process development from food waste via anaerobic fermentation, including effect factors, control methods, and optimum conditions of the biohydrogen production process, is provided.

In Chapter 1, Anaerobic Fermentation Process for Biohydrogen Production From Food Waste, food waste treatment and disposal technologies are introduced, including food waste characteristics, generation yield and prediction models, and treatment and disposal methods (such as anaerobic fermentation for biogas and organic acid, composting, making protein feed for animal, crushing for discharge, landfill, and incineration). The principles and processes of biohydrogen production, such as the photosynthesis biohydrogen system, photolysis biohydrogen system, water–gas exchange reaction biohydrogen production system, photosynthetic–fermentation hybrid biohydrogen production system, anaerobic fermentation biohydrogen production system, and anaerobic fermentation biohydrogen fermentation technology are also described in depth. At the same time, the process control and environmental influence factors of anaerobic fermentation biohydrogen production are also given, including organic by-production, partial pressure of hydrogen, carbon dioxide content, pretreatment methods, pH, temperature, oxidation–reduction potential, hydraulic retention time, stir speed, C/N ratio, organic nutrient, inorganic nutrient, and substrate type.

In Chapter 2, Optimization of Biohydrogen Production With Additives and Inoculum From Food Waste, the optimization of process parameters for enhancment of the biohydrogen yield is fully covered, including the different inoculation sludge sources, proportion optimization of inoculation sludge and food waste, heat pretreatment of inoculation sludge, CaCO3/MnCl2/NaCl addition, alkali agent dosage, initial moisture content, sludge inoculation rate, temperature of the fermentation system, Na+ and NH3–N concentrations, Fe with different valence, and nitrogen sources. The effects of the optimization of conditions are evaluated by the acidification process and biohydrogen production yield. The semicontinuous anaerobic rotary drum (SARD) reactor designed for the evaluation of the simulative process of adding aged refuse and laundry detergent under the condition of sludge inoculation is described. Moreover, biodynamic properties and biohydrogen production processes of different inoculated microorganisms, and polymerase chain reaction–denatured gradient gel electrophoresis characterization of microbial populations are also provided for the mechanism analysis of biohydrogen production enhancement.

In Chapter 3, Pretreatment and Aged Refuse Dosage on Biohydrogen Production From Food Waste, biohydrogen generated from food waste in the presence of granual sludge and aged refuse and via thermal hydrolysis is described, involving food waste content, granual sludge content, inoculation rate, and anaerobic fermentation of air-dried and fresh food waste. The analysis process includes the satisfaction function, satisfaction of multiple response values function method, biohydrogen production rate and yield, propionic acid concentration, butyric acid concentration, dissolution of food waste solids during thermal hydrolysis, soluble chemical oxygen demands and total organic carbon variation, NH3–N variation, volatile fatty acids variation, dehydration capacity of food waste, pH variation, acidification characteristics, and the mechanism of biohydrogen production enhancement with aged refuse. In addition, continuous fermentation and a pilot system are designed and conducted for evaluating the biohydrogen production improvement of thermal hydrolysis, including the design and construction of an anaerobic reactor, operation of the reactor, start-up characteristics of complete equipment at a medium temperature, and the characteristics of medium- and high-temperature operations.

In Chapter 4, Simultaneous Anaerobic Fermentation Biohydrogen and Biomethane Production From Food Waste, simultaneous anaerobic fermentation biohydrogen and biomethane production are introduced, including the effects of adding alkaline wastewater, iron concentration, CaCO3 and NaCl addition, moisture content, and the synergistic effect of aged refuse and alkaline additives on biohydrogen production of food waste. Methane fermentation from biohydrogen fermentation residues, involving static and dynamic methane fermentation, is also described. A 10 L biohydrogen production reactor is further designed, and therein, the biohydrogen and methane production process, joint operation of combined biohydrogen production and methane production equipment, gas phase component and production, and pH and volatile solid variation are analyzed. Finally, the design and operational management of biohydrogen and methane production treatment plants for food waste are introduced, including the sorting and oil recovery unit, pretreatment unit, discharge and dewatering unit, biogas purification unit, and process equipment.

In Chapter 5, Combined Anaerobic Fermentation Biohydrogen and Biomethane Production for Sewage Sludge and Food Waste, the influence factors such as pretreatment conditions, initial pH, and different additives on biohydrogen production from sewage sludge fermentation are given to explore the optimal biohydrogen production parameters and instruments, including experimental design pretreatment methods for sludge, biohydrogen production with different pretreatment methods, disintegration characteristics of sludge, biohydrogen-producing bacteria and hydrogen-consuming bacteria, effect of initial pH on hydrogen production, and effect of pretreatment and substrate addition on hydrogen production. The effect of inhibitors on the biohydrogen production process of sludge anaerobic fermentation is also introduced, including experimental design, variation of biohydrogen and biomethane content, variation of substrate before and after fermentation, and mechanism of biohydrogen generation. Landfill leachate and fresh food waste are selected for enhancing biohydrogen production from sludge, and heat pretreatment of sludge, acid and alkali pretreatment of sludge, self-acidification of food waste on biohydrogen production, characteristic variations of food waste and sludge, and combined anaerobic fermentation of hydrogen production from heat-treated sludge and fresh food waste are characterized. The mechanisms of combined anaerobic fermentation, including degradation of sugar and protein, variation of the main liquid-phase products during the fermentation process, impact test of single factor, and response surface optimization are also shown.

In Chapter 6, Design and Optimization of Biohydrogen Production Reactor, an innovative anaerobic fermentation reactor for biohydrogen production named SARD is designed and operated for semicontinuous fermentation using food wastes as the source material. The design of SARD, including design ideas, DANO rotary drum, overall structure and working principles, and structural parameters are introduced. Based on the SARD, the operation modes, including feeding of food waste, food waste and sludge, gradually increased load of food waste and sludge feeding, length–diameter ratio, reflux ratio, rotation rate and stirring time, and substrate analysis under the optimal operation condition are described in depth. In comparison with conventional continuous stirred tank reactors and push-flow reactors, its economic and environmental benefits are also highlighted.

In Chapter 7, New Development of Nutrition Recovery From Food Waste, the new developments in nutrition recovery from food waste are introduced, such as the synthesis composite hydrogel fertilizers from food waste, remediation of contaminated soil with composite hydrogel fertilizers, and efficient capture of aqueous humic acid using a functionalized stereoscopic porous activated carbon based on poly(acrylic acid)/food-waste hydrogel. Characterization of LR-g-PAA/MMT/urea, water absorbency and swelling capacity, migration and transformation of heavy metals, variation of soil physical and chemical properties, bioavailability variations of heavy metal contents in soil, mechanism of soil remediation, characterization of poly(acrylic acid)/food-waste hydrogel and the modified SPAC with APTES adsorbent, adsorption performance toward humic acid, and real-life applications for mature landfill leachate are provided in detail.

Those who would benefit from reading this book include solid waste engineers, managers, technicians and maintenance staff, recycling coordinators and government officials, undergraduates and graduates, and researchers. In addition, it is envisaged that the book also has great potential to enhance the international exchange in knowledge and cooperation of environmental researchers worldwide.

This book is partially financially supported by the National Key R&D Program of China (no. 2018YFC1901400), Social Development Programs of Science and Technology Committee Foundation of Shanghai (nos. 19DZ1204600, 19DZ1204703, and 18DZ1202604), National Natural Science Foundations of China (nos. 51878470 and 51678419), and the Fundamental Research Funds for the Central Universities (no. 22120190232).

Summary

Food waste has received increasing concern due to its ever-increasing product and environmental security problems. It is necessary to explore new methods of food-waste disposal and protect the environment effectively. This book provides a comprehensive description of the technical aspects of biohydrogen production from food waste via anaerobic fermentation, including effect factors, control methods, and optimum conditions of biohydrogen production process. Biohydrogen, generated from food waste anaerobic fermentation, is an effective, environment-friendly, and renewable alternative energy source. This book also provides an in-depth discussion of food waste hydrogel synthesis and its utilization, the principles and process progress of fermentation biohydrogen production, enhanced biohydrogen production with the presence of aged refuse, parameter designs for semicontinuous anaerobic rotary drum biohydrogen production reactors, and optimization of biohydrogen production with the addition of additives and inoculums, and equipment and scale-up pilot tests for simultaneous biohydrogen and methane production from food waste.

Abbreviations

AA acrylic acid

APTES aminopropyltriethoxysilane

ATP adenosine triphosphate

BOD5, or BOD biological oxygen demands

BSA or BSE bovine serum albumin

C/N carbon and nitrogen ratio

CCD central composite design

CSTR continuously stirred tank reactor

CM-IOH inorganic–organic hybrids

CEC cation-exchange capacity

CODCr or COD chemical oxygen demands

FW food waste

HRT hydraulic retention time

HAc acetic acid

HA humic acid

KPS potassium persulfate

LR leftover rice

LLR leaching loss ratio

MMT montmorillonite

MBA N,N′-Methylenebisacrylamide

MSW municipal solid waste

NH3-N ammonia nitrogen

NADH nicotinamide adenine dinucleotide

NADPH nicotinamide adenine dinucleotide phosphate

ORP oxidation–reduction potential

PCR-DGGE polymerase chain reaction-denatured gradient gel electrophoresis

PCR-RELP polymerase chain reaction-restriction fragment length polymorphism

PAA polyacrylic acid

PFR plug flow reactor

SARD semicontinuous anaerobic rotary drum

SPFRD spiral-plug-flow rotation drum anaerobic bioreactor

SPAC stereoscopic porous–activated carbon

SPAC-NH2 the modified SPAC with APTES

SCOD soluble chemical oxygen demands

SOC soil total organic carbon

SS suspended solid

TN total nitrogen

TP total phosphate

TOC total organic carbon

TS total solid

VS volatile solid

VSS volatile suspended solid

VFA volatile fatty acid

Chapter 1

Anaerobic fermentation process for biohydrogen production from food waste

Abstract

In this chapter, food waste (FW) treatment and disposal technologies are introduced, including FW characteristics, generation yield and prediction models, and treatment and disposal methods (such as anaerobic fermentation for biogas and organic acid, composting, making protein feed for animals, crushing for discharge, landfill, and incineration). The principles and process progress of biohydrogen production such as the photosynthesis biohydrogen system, photolysis biohydrogen system, water gas exchange reaction biohydrogen production system, photosynthetic–fermentation hybrid biohydrogen production system, anaerobic fermentation biohydrogen production system, and anaerobic fermentation biohydrogen fermentation technology are also fully introduced. At the same time, the process control and environmental factors influencing anaerobic fermentation biohydrogen production are also described, including organic by-production, partial pressure of hydrogen, carbon dioxide content, pretreatment methods, pH, temperature, oxidation–reduction potential, hydraulic retention time, stir speed, C/N ratio, organic nutrient, inorganic nutrient, and substrate type.

Keywords

Food waste; sources and characteristics; anaerobic fermentation process; principles of biohydrogen production; digestion; organic waste

1.1 Food waste sources

Food waste (FW), mainly refer to cooked food, also known as kitchen waste or swill, is waste and residues produced during food processing by households, the food and beverage industry, and canteens. The main components of FW are vegetables, vegetable oil, animal oil, meat, bone, and so on, and may be a mixture of cooked and uncooked waste. The main chemical composition includes starch, cellulose, protein, lipids, and inorganic salts as well as a small amount of nitrogen, phosphorus, potassium, calcium, sodium, magnesium, iron, and other trace elements, which can provide a good environment for pathogenic microorganism growth and reproduction resulting in the spread of diseases. Because of its high water content and low calorific value, FW has lacked proper treatment and utilization methods.

1.2 Food waste characteristics

In general, FW has the following characteristics:

1. Large production. It may occupy around 10–40% of the municipal solid waste for a city and should be collected and treated in a timely fashion.

2. High moisture content and perishable. It is difficult to collect, transport, and handle FW if it has a high moisture content. The leachate can pollute the surface water and groundwater through surface runoff and infiltration. Because of the high organic matter content and moisture, FW rots quickly under the action of bacteria.

3. Rich in organic matter and trace elements. FW possesses a high organic matter content, which contains a number of nutrient species. In addition, due to contact with metal containers, FW contains less heavy metals, which makes it conducive to reuse.

4. Environment pollution and disease transmission. It will cause environmental pollution when odorous gases (such as H2S, NH3-N, mercaptan) are discharged into the environment directly if there are no closed and harm-reducing measures used during the processes of transportation, storage, and disposal. Exposed FW can attract and breed a large number of mosquitoes and rodents, which become inevitably a medium for the transmission of disease. In addition, putrid FW contains a large number of Salmonella, Staphylococcus aureus, hepatitis virus, and other pathogenic microorganisms, causing a variety of diseases. Therefore, besides centralized and large-scale treatment, in situ disposal technologies are used.

The physical, biological, chemical, and pollution characteristics of FW are summarized in Tables 1.1–1.4.

Table 1.1

Table 1.2

Table 1.3

Table 1.4

As shown in Table 1.1, the moisture content of FW is about 80%. This high moisture content makes the bulk density of garbage close to that of water, basically around 1.00 kg/m³. The water content must be reduced in order to meet the requirements of the subsequent recycling process.

The element analyses and biological–chemical characteristics of FW are shown in Tables 1.2 and 1.3. It can be seen that the high content of organic matter and the large proportion of biodegradable components in FW are very suitable for biochemical treatment. The trend of biochemical recycling of FW is mainly through aerobic composting and anaerobic fermentation. The biodegradability is 60%–80%, and the organic matter content is 84%–93%. The crude fat content is about 20%–40%, and the salt content is about 2%. The national diet of China is heavy in oil and salt, especially in restaurants, which leads to the high oil and salt contents of FW, making subsequent disposal more difficult.

As shown in Table 1.4, some heavy metals are detected in FW. Water and soil are polluted by heavy metals to varying degrees. Heavy metals in the air are deposited in water and soil, accumulated through the enrichment of plants and animals in vegetables, meat, and poultry, and will eventually be consumed by humans. Contaminants from gutter oil, low-quality cooking utensils, and other products can also enter the food system through cooking. The presence of heavy metals not only result in ill health to the consumer but also affects the end recycling of food and kitchen waste. The existing recycling methods are mainly biochemical. The microorganisms in the biochemical reaction are more sensitive to heavy metals, so if there are many heavy metals in food and kitchen waste, the pretreatment will undoubtedly be increasingly difficult. The prevention and control of heavy metal pollution in food calls for a two-pronged strategy concerning both environmental pollution control and food safety and hygiene management to ensure food safety.

1.3 Food waste generation/yield and prediction models

There are many factors influencing the amount of FW generated, among which the main ones are internal, social, and individual factors. Internal factors directly lead to changes garbage production, such as population size, population sex ratio, and residents’ living standards. Social factors mainly include the social code of conduct, social ethics, laws, and regulations. Individual factors mainly are individual living habits, behavior patterns, education level, etc. Generally, only the internal factors are taken into account. The internal factors influencing the production of food and kitchen waste mainly include population, urban economic development level, and residents’ living standards. Considering the actual situation in downtown Shanghai, four groups of influencing factors were selected for modeling: the resident population reflecting the population situation, the GDP reflecting the social and economic development level, and the per capita disposable income and consumption level of urban residents reflecting the living standard.

1.3.1 Multiple linear regression model

After summarizing the four groups of influencing factors, the linear correlation coefficients between the influencing factors and FW production can be obtained. The mathematical model is as follows:

(1.1)

where Y is the predicted value (×10⁴ t/a) of the food and kitchen waste production in downtown Shanghai; X1 is the permanent population (10,000 people); X2 is GDP (100 million yuan); X3 is the per capita disposable income of urban residents (yuan); and X4 is the per capita consumption expenditure of urban residents (yuan).

The quantity of living garbage in central city districts can be obtained from their 2007–2015 statistical yearbooks. Based on the linear proportional relationship between the quantity of FW and domestic solid waste (the ratio of FW and domestic solid waste is set at 0.1), the actual production of FW between 2007 and 2015 is concluded. At the same time, basic data are obtained (permanent urban population, regional GDP, per capita disposable income, and per capita consumption expenditure of urban residents), as shown in Table 1.5.

Table 1.5

The data in Table 1.5 are substituted into the model, and the model parameters b0, b1, b2, b3, and b4 are achieved by the least squares method, and the prediction model of the FW production in downtown Shanghai is as follows:

(1.2)

The statistically tested prediction model shows that F=1.187035>F0.05=0.43601632 on the condition of a 95% confidence level and α=0.5 significance level, which indicates that the linear relationship between the amount of FW produced and the selected influencing factors is significant. The prediction data can be calculated beyond 2015 using formula (1.2).

1.3.2 Yield prediction of food waste

According to the outline of the 13th 5-year plan for Shanghai’s national economic and social development, the annual growth rate of Shanghai’s GDP is expected to be around 7% during the 13th 5-year plan period. The real growth rate of per capita disposable income is lower than the growth rate of per capita GDP, and per capita consumption expenditure is closely related to disposable income. Therefore per capita disposable income and per capita consumption expenditure are also calculated at an annual increase of 6%. Based on the previous prediction model, the predicted results of FW production in Shanghai during 2016–20 are obtained, as shown in Table 1.6.

Table 1.6

1.4 Treatment and disposal methods of food waste

1.4.1 Anaerobic fermentation

Anaerobic digestion has been developed as a preferred resource recycling technology for FW treatment. Anaerobic digestion, namely, biogas or methane fermentation, is a method for degrading complex organic matter into inorganic compounds, methane, carbon dioxide, and other gases under anaerobic conditions with the function of anaerobic fermentative bacteria, acetic acid bacteria, methane-producing bacteria, etc. A general anaerobic digestion flowsheet for FW and kitchen waste is shown in Fig. 1.1.

Figure 1.1 Typical general anaerobic digestion flowsheet for food waste and kitchen waste.

According to the overall process flow, the project is mainly composed of the following systems:

1. FW pretreatment system: The food waste within the service scope is collected and sent to the comprehensive pretreatment system. After the separation of grease and residue, the feeding requirements of anaerobic fermentation are met.

2. Kitchen waste pretreatment system: Kitchen waste within the service scope is collected and sent to the comprehensive pretreatment system. After the pretreatment of kitchen waste and the separation of impurities such as residues and metals, the feeding requirements of anaerobic fermentation are met.

3. Wet anaerobic and dehydrating system: After pretreatment, the FW is mixed in a homogeneous tank and then enters the wet anaerobic fermentation tank for anaerobic fermentation, so as to effectively utilize the organic matter to produce methane and recyclable resources. After anaerobic fermentation, the slurry is dehydrated by a centrifuge until the moisture content is no more than 80%. The dehydrated biogas residue enters the biogas residue drying system, and the dehydrated biogas slurry is collected and discharged.

4. Dry anaerobic and dehydrating system: Kitchen waste after pretreatment is temporarily stored in an organic matter buffer pit and then mixed in a dry anaerobic tank for anaerobic fermentation, so as to effectively utilize organic matter to produce methane and recyclable resources. After anaerobic fermentation, the biogas residue is dehydrated by screw extrusion and vibrating screen successively, and the residue is transported for incineration. The biogas slurry is further dehydrated in the centrifugal dehydration system until the moisture content is less than 80%. The biogas residue enters the subsequent biogas residue drying system, and the dehydrated filtrate is discharged.

5. Biogas purification and storage system: After biogas purification meets the requirements for boiler use, it is temporarily stored in the biogas cabinet for subsequent use.

6. Biogas boiler and heat exchange system: The purified biogas is used for the fuel and gas steam boiler, and the saturated steam generated by the steam boiler is used as the heat source for kitchen waste pretreatment, dry anaerobic tank heating, and biogas residue drying.

7. Biogas power generation system: Part of the purified biogas is used for steam generation in the steam boiler, and the rest is fed into the gas internal combustion engine for biogas power generation, and the generated electricity is transferred to the switch station.

8. Biogas residue drying system: The biogas residue after dehydration by wet and dry anaerobic centrifugation enters the biogas residue drying system. It is dried until the moisture content is no higher than 40% and then shipped out.

When the overall technical line is involved, the first priority is to meet the treatment needs of different wastes and to take different pretreatment and anaerobic technologies, respectively. The second is to set up treatment and recycling facilities for biogas slurry, biogas residue, biogas, and other products, in order to give them full access to the advantages of collaborative processing and to reduce investment and work.

1.4.2 Aerobic composting

Composting was the earliest method of municipal waste treatment because of its practicability and simplicity. Since the 1990s the main method for municipal waste treatment has been landfill, which has transited to incineration gradually. In the composting system, the organic matter of FW is degraded via microbial fermentation to form humus, which can be used as a fertilizer or soil conditioner. Besides, composting can obtain a 40% decrement and increase the content of nutrients such as organic matter, nitrogen, phosphorus, and potassium in the soil, realizing the recycling of resources.

The composting process is carried out by microorganisms, supplemented by air oxidation, and finally humus is achieved. In a well-treated degradation process, approximately 50% of organic matter is converted to H2O, CO2, NH3, inorganic salts, and energy. About 20% of the remaining organic matter becomes humus substances after complex metabolic transformation. The loss of bioorganic matter in the whole process is about 30%–60%. In addition, if the oxygen content is insufficient, the pile will be partially anoxic or anaerobic and produce volatile organic compounds, NH3, CO, NxOy (NO and N2O), and CH4, which cause secondary pollution and reduce the retention of nutrients in compost products.

1.4.3 Making protein feed

FW contains a lot of organic matter. The new technology using FW to produce high-quality protein feed considers the protein, cellulose, carbohydrates, and other organic ingredients present as a carbon source. It creates a medium artificially through biochemical treatment after adding the appropriate nitrogen source and trace elements. This medium can promote the proliferation of bacteria; produce single-cell protein so that the product is rich in bioactive peptides, amino acids, nucleic acid degradation products, nucleotides, and nucleosides; and become a high-quality multiprotein feed. The main methods include microbial fermentation and physical drying. This method can achieve the recycling of FW and alleviate the serious shortage of feed raw materials to some extent, but the feeding of FW has a potential risk to the food chain and may cause animal homology pollution.

1.4.4 Crushing

It is common to use an FW disposer in the kitchen to discharge crushed FW into the municipal drainage pipe network in some countries. The developed mechanical grinding device for FW is used to cut and mix the various FW in the liner of the device into a sewer through high-speed running blades, which can partly solve the problem of sewer blockage. However, the direct discharge of FW often produces sediments and odor, breeds pathogens, mosquitoes, and flies, and causes disease transmission. The agglomeration of oil will cause blockage of drainage pipes and reduce the drainage capacity of urban sewers. A high oil content will also increase the load of urban sewage treatment plants and inevitably produce secondary pollution.

1.4.5 Landfill

Presently, sanitary landfill is remains the main disposal method. FW commonly consists of bound water and degradable substances, such as sugar, protein, and fat. High FW-content municipal solid waste (MSW) landfill (HFWC-MSWL) has the characteristics of rapid hydrolysis, rapid production of large leachate, and rapid gas production. Therefore HFWC-MSWL typically has a high leachate level, which has a significant impact on the hydrological characteristics of MSW. The accumulation of high leachate from FW landfill results in a large amount of aerated water, accounting for 21–28% of total leachate. In the HFWC-MSW of southern China, raw leachate accounts for more than 30% of the waste placed. The rapid hydrolysis of FW in HFWC-MSW results in a 13% loss of landfill gas (LFG) capacity, which not only wastes a lot of organic resources but also affects the purity of the entire LFG and causes energy waste.

1.4.6 Drying and incineration

Incineration is a high-temperature thermochemical treatment technology for MSW, and is also a way to recycle heat energy from MSW. In theory, incineration can reduce waste by 75%–95%, but in practice, it is only close to 50% due to the issues of maintenance and waste supply. It is similar to waste reduction and recycling. The moisture content of organic solid waste is generally high, and the calorific value is not high enough. For example, the calorific value of FW is only about 2300 kJ/kg, while the calorific value of slightly dehydrated sludge is about 863 kJ/kg because the municipal sludge contains a lot of organic matter and a certain amount of fiber lignin. In addition, the minimum calorific value for incineration operation is 4500 kJ/kg, and the calorific value for stable power generation is 6000 kJ/kg. Incineration of organic solid waste requires a large amount of fuel, not to mention the possible dioxin and heavy metal pollution, and it not only consumes energy but also wastes organic waste resources.

It has been proposed that the cocombustion of FW and pulverized coal can reduce the amount of CO2 produced by fossil fuel combustion and also decrease the pressure of FW on landfills. However, due to the high moisture content and high fiber content of FW, it reduces the overall calorific value and combustion efficiency in the cocombustion process. What is worse, it increases the emission of toxic gases and causes scaling in the combustion chamber.

1.5 Principle and process progress of biohydrogen production

Hydrogen is the lightest of all elements, and is a colorless, tasteless, and odorless gas. Under standard conditions the mass of 1 L of hydrogen is 0.089 g. Hydrogen can become a colorless liquid under 101.325 kPa, −252.8°C. Hydrogen is one of the best carriers of energy for the future and has a wide range of applications. Fossil energy reserves are limited and can cause serious environmental pollution during the application process. Thus, the utilization of hydrogen as a power fuel engine is also being developed and its advantages are as follows:

1. High calorific value. The calorific value of hydrogen is 1.28×10⁴ J/m³, which is three times higher than that of gasoline.

2. Abundant resources. Hydrogen can be described as a renewable energy, which can be generated from water because there are two hydrogen atoms in one water molecule.

3. Clean and pollution free. The final product after hydrogen combustion is water, which is environment friendly.

There are many bottlenecks in the preparation of hydrogen, which is also the reason why hydrogen has not been widely popularized and applied at present. The conventional methods of hydrogen production are adopted to electrolyze water or pyrolyze petroleum and natural gas, which need to consume a large amount of power or mineral resources, and the production costs are generally higher. Biohydrogen production technology, using a microbial metabolism process to produce hydrogen, is an effective way to solve those problems. The raw material used can be organic wastewater and the production the process is clean and energy-saving, and is gaining increasing attention.

1.5.1 Photosynthesis of the biohydrogen system

The light synthesis of water is a biological process that converts solar energy into useful and stored chemical energy. The reaction is as follows:

(1.i)

The method of light synthesis has the same biological process in plants and algae, except that the hydrogen production is accompanied by algae rather than carbonaceous biomass. Biohydrogen production with Chlorella anaerobic conditions after vaccination takes several minutes to several hours, for mainly inducing synthesis or activation of enzymes involved in hydrogen metabolism. Hydrogenase utilizes the ferritin to provide electrons that combine H+ protons to form hydrogen molecules. The synthesis of H2 supports the continuous flow of electrons through the electron transport chain, which can produce the required adenosine triphosphate (ATP) synthesis.

1.5.2 Photolysis of the biohydrogen system

Cyanobacteria can release hydrogen via the following two steps:

(1.ii)