1 Biowastes for Energy An Introduction
Alfred Nkhama, Muhammad Rizwan Sulaiman, Jonghyun Choi, and Ram K. Gupta
Pittsburg State University
DOI: 10.1201/9781003178354-2
Contents
1.1 Introduction
1.2 Source and Significance of Biowastes
1.2.1 Biowastes from Forest and Wood Processing Industries
1.2.2 Biowaste from Food Processing
1.2.3 Biowaste from the Paper Industry
1.2.4 Biowaste from Municipal Solid
1.2.5 Animal Waste
1.3 Pretreatment of Biowaste
1.3.1 Pretreatment of Animal Fat Waste
1.3.2 Lignocellulosic Waste Pretreatment
1.3.3 Pretreatment of Waste Cooking Oil
1.3.4 Removal of Inhibitory Compounds and Salts
1.4 Biowaste to Bioenergy
1.4.1 Biodiesel from Biowaste
1.4.2 Biogas from Biowaste
1.4.3 Bioelectricity from Biowaste
1.4.4 Bioalcohol from Biowaste
1.4.5 Electrochemical Energy from Biowastes
1.5 Conclusions
References
1.1 Introduction
Today’s modern society is in dire need of energy since every technological advancement and day-to-day living are supported by energy. For decades, the main power supplies have primarily been based on limited and nonrenewable fossil fuels. These fossil fuels were earlier consumed excessively, which resulted in drastic consequences such as ozone layer depletion, environmental degradation, air pollution, global warming, and deforestation. With the continuous increase in the global population and increasing need for energy for daily activities, fossil fuels may not satisfy the energy demand in the future. Importantly, the current hydrocarbon resource discoveries are getting smaller than those found in the past, which implies that they are being depleted. Therefore, the exploration of clean and sustainable energy, such as solar energy, hydropower, tidal energy, bioenergy, wind energy, and geothermal energy, is necessary for a sustainable future.
Various stakeholders, including international communities, governments, and individuals, were taking an interest in developing a sustainable future based on the techniques established over the past few decades to substitute hydrocarbon-derived fuels with renewable energy sources. Among various renewable energy resources, including solar energy, wind energy, tidal energy, and fuel cells, energy production using biowastes could be a cost-effective approach and provides a clean solution to ever-growing wastes. Biowastes derived from living organisms or having an organic origin are potential sources of chemicals and energy.
1.2 Source and Significance of Biowastes
Wastes such as crop residues, livestock effluents, sawdust, and sewage treatment products are biomass that can be decomposed under aerobic and anaerobic conditions to convert into value-added products [1,2]. Biowaste management is an economic approach that plays a crucial role in safeguarding the environment and enhancing living standards. Most of the biowastes are landfilled or burned to avoid trash accumulation. The landfill process requires human resources, energy, and a large dump area, while burning produces undesirable gases. Both processes severely affect the global environment and the health of living beings. To overcome these issues, waste management can be integrated alongside energy-generating technologies. Biowaste treatment with different biowaste-to-bioenergy (BtB) techniques is an executable way for treating biowaste as well as producing energy [3,4 and 5]. The worldwide market value of BtB technology is around $25 billion and is expected to reach $40 billion by 2023 [6]. Various biological techniques such as fermentation, esterification, anaerobic digestion, and electro-fuel cells are applied to convert waste into energy. Other physiochemical processes such as gasification, pyrolysis, landfills, and incineration are also commonly used. The classification of biowastes is based on the origin of waste and requires different strategies for pretreatment and transformation into bioenergy. The following are the classes of biowastes and processes to convert them into bioenergy.
1.2.1 Biowastes from Forest and Wood Processing Industries
Forest wastes can be categorized into two groups: (i) waste produced during wood reaping from the forest and (ii) waste generated during wood processing in industries such as plywood and timber. Unutilized forest wastes could result in forest fires that can lead to economic damage, soil degradation, environmental pollution, and wildlife deterioration. The use of forest biomass to generate energy can minimize forest fires and act as a suitable alternative for sustainable energy. Wood wastes are also generated via many other activities such as thinning of plantations, constructions, and furniture industries. Furniture industries mostly generate trim and sawdust. The biomass generated from different sources contains different amounts of cellulose, lignocellulose, and lignin, which impact energy production efficiency. The content of the components helps to decide the pretreatment steps in BtB. Biomass with little lignin is regarded as a good raw material for generating energy [5].
1.2.2 Biowaste from Food Processing
The food processing industry is one of the rapidly growing industries in the world. The continuously growing population requires even more supermarkets and restaurants to supply and satisfy the need for food. Breweries, edible oil production, bakeries, juice factories, meat processing, etc., are a few food industries that produce a large number of biowastes. The wastes generated from the food industries can be categorized into liquids or solids. Fruits that do not meet and comply with the set standards are considered solid wastes in fruit industries or grocery stores. The so-called liquid wastes are obtained after washing meat, fruits, and vegetables and are made of starch, sugar, and organic matter. Other sources of liquid waste are oils or grease and household liquids. Vegetable oil used in cooking food is discarded after certain uses. Food-derived wastes can be processed and transformed into useful products such as enzymes, biofuels, and nutraceuticals by biorefinery, thus helping reduce waste from the environment.
1.2.3 Biowaste from the Paper Industry
The paper and pulping industries are considered to be the third largest contributor to pollution [7]. The process of breaking bonds in the structure of wood is known as pulping. The pulping process in the paper industry is carried out by applying different mechanical and chemical processes [7]. The employed pulping method also determines the yield and quality of the pulp produced. The disposable papers such as napkins and newspapers are produced by mechanical processes. Special papers such as rayons and photographic films are produced by sulfite pulping and mostly consist of cellulose. Waste in solid form is mostly generated during pulping, de-inking, and wastewater treatment processes. It is estimated that 40–50 kg of sludge is produced during the production of one ton of paper [8]. The control and management of such wastes is a challenge. Anaerobic digestion or different technologies have been employed to efficiently deal with this challenge by transforming these wastes into energy.
1.2.4 Biowaste from Municipal Solid
The economic booming, population growth, and urbanization result in the rapid increase in municipal solid wastes. A person produces 100–400 kg of municipal solid wastes yearly. About 2.2 billion tons of municipal solid wastes are projected to be produced every year until 2025, which would be increased to 4.2 billion tons by 2050 [9]. Many challenges have been faced by the authorities and governments in developing nations in managing such wastes. Municipal solid wastes are mainly managed by four methods: landfills, thermal, recycling, and biological treatments.
1.2.5 Animal Waste
Animal wastes include animal dung, meat products from slaughterhouses, and wastes from the dairy/po...
