Biomethane

Developments and Prospects

Sonil Nanda, Prakash K. Sarangi, Sonil Nanda, Prakash K. Sarangi

• Publisher: Apple Academic Press
• Year: 2022
• ISBN:
  9781000565638
• Edition: 1
• Topic: Ciencias biológicas
• Subtopic: Bioquímica

This book presents a comprehensive synopsis of the production and utilization of biomethane along with important recent advances. Biomethane production offers valuable alternative energy solutions for the replacement of fossil fuels to lessen environmental impacts and strategize for mitigating global warming and climate change.

Chapters first focus on the production of biogas (or biomethane) with emphasis on the different biomass utilization for industrial and domestic applications and describe the characteristics, parameters, and process design of anaerobic digesters for biomethane production from waste biomass. The book then goes on to discuss advanced genetic engineering tools and techniques to enhance biomethanation and biomethane production. The volume also offers a state-of-the-art review of anaerobic digestion of biogenic solid wastes, the impact of different chemical pretreatment processes and products, and the influence of operating parameters on biomethane yields.

Differentiating between the thermochemical technologies (e.g., gasification and pyrolysis) and biological technologies (e.g., anaerobic digestion) for biomethane production, the book assesses some recent advancements in biomethane production along with its socioeconomic impacts and applications. Other topics include gasification technology and syngas cleaning for biosynthetic natural gas production, the use of catalysts for enhanced synthetic natural gas production, biohythane fuel produced from microbial fermentative pathways, and more.

Biomethane: Developments and Prospects offers valuable insight and information on the current status of production and utilization of biomethane that has cross-disciplinary value in biotechnology, fermentation technology, bioprocess engineering, chemical engineering, and environmental technology with a common interest in biofuels and bioenergy.

CHAPTER 1 Utilization of Waste Biomass Resources for Biogas Production

SHANKAR SWARUP DAS,¹ PRAKASH K. SARANGI,² and SONIL NANDA³

¹Department of Farm Machinery and Power Engineering, Central Agricultural University, Ranipool, Gangtok, India E-mail: [email protected] (Shankar Swarup Das)

²Directorate of Research, Central Agricultural University, Imphal, Manipur, India

³Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

ABSTRACT

Alternative fuel generation has drawn the attention of researchers due to the forthcoming warning of fossil fuel insufficiency. This has led to the utilization of various alternative and sustainable biomasses for biofuel production. Biofuel derived from biomass are considered the major solution to meet the future challenges raised by fossil fuel, unusual climate change, and greenhouse gas emission. Hence, biomass, which is rich in carbohydrates, can also be effectively converted into hydrocarbons. Biomass can be transformed into biofuels such as bioethanol, biodiesel, biohydrogen, and biogas to use it widely for transportation, industrial, and domestic applications. Many developments in the production of biofuels and biogas have been reported in recent years. This chapter broadly focuses on the production of biogas with emphasis on the different biomass utilization for various industrial and domestic applications.

1.1 INTRODUCTION

Fossil fuel contributes a major part in the scenario of energy supply in the modern world in the form of coal, crude oil and gasses (Sarangi et al., 2012; Nanda et al., 2015). The demand for energy supply has been extensively increased due to the inherent power generation, industrialization, and transportation. Coal as solid fuel is mainly used for power generation in the thermal power plants, whereas crude oil in the form of petrol and diesel are used for the transportation sector and the gasses for domestic purpose as cooking gas (Sarangi and Sahoo, 2010; Rana et al., 2020). The escalating usage of fossil fuel and natural gas has led to the environmental problems of greenhouse gas emission and insufficiency from the sources. Many researchers have reported that fossil fuel sources throughout the world will last up to 25 years, and there is a need for alternative sources such as renewable energy (Sarangi and Nanda, 2018, Sarangi and Nanda, 2019; Bhatia et al., 2020).

Biofuels are the most prominent source of renewable energy and are expected to be the major replacement of the current fossil fuel. These fuels are gaining more popularity due to their environment-friendly and sustainable nature (Nanda et al., 2018; Nanda et al., 2019). It is also observed that the biomass takes an equivalent amount of CO₂ during its growth and release in consumption, making biofuels carbon-neutral (Baçaoui et al., 1998). These are generally considered as organic such as forest residues, agricultural residues, grass cuttings, animal manure, sewage sludge, etc., (Gong et al., 2017; Nanda et al., 2016; Nanda et al., 2020; Sarangi et al., 2020; Sarangi and Nanda, 2020; Siang et al., 2020).

In this chapter, the overall possible paths for the production of biogas with the technologies used for the conversion of biomass to biofuel is discussed. Historical indication shows that the biogas was mainly used for heating water for bath purposes during the mid of the sixteenth century at Persia (Cheng, 2010). Biogas predominantly contains CH₄, which is generally produced by the anaerobic digestion process where the organic wastes are degraded by methanogenic bacteria without oxygen (Bessou et al., 2009). It is considered clean and renewable energy that which is a substitute for natural gas to be used for cooking, water heating and electricity generation (Andrea and Fernando, 2012).

Biogas is available in the gaseous form at room temperature and pressure, unlike the liquid form of liquefied petroleum gas (LPG). Anaerobic digestion or methanation is performed in four basic steps such as hydrolysis, acetogenesis, acidogenesis, and methanogenesis. In the case of the hydrolysis process, the rate of liberation of gas is limited because the polymers contain complex polymers. Biomass can be subjected to microbial attack in case of the pretreatment processes (Hall and Scrase, 1998). Hence the pretreatment can be physically done like irradiation, biological treatments by enzymes or fungus, chemical treatment with oxidation, acids, alkalis. Sometimes it can be done by a combination of all these processes (Omer, 2012). Acidogenes in the anaerobic digestion process is nothing but the acidogenic microorganisms further spitted into biomass after hydrolysis. In this case, the fermentative bacteria produce NH₃, H₂, CO₂, H₂S, fatty acids, alcohols and carbonic acids apart from producing an acidic environment. Mostly the acidogenic bacteria break down the organic matter of the biomass to produce a large quantity of useful methane under the acetogenesis process. The fundamental steps of the conversion of biomass to biogas using a biodigester or anaerobic digester are shown in Figure 1.1.

FIGURE 1.1 Fundamental steps of biomethanation in a biodigester.

The final step of the anaerobic digestion process is methanogenesis, which constitutes the final products of acetogenesis, and a few intermediate products of hydrolysis and acidogenesis (Omer, 2015). The main mechanism in methanogenesis is to convert CO₂ into methane and by consuming H₂, which involves the path of acetic acid, which gives two products in anaerobic digestion like CH₄ and CO₂ (Taherzadeh et al., 2008).

1.2 BIOCONVERSION PROCESS

The transformation and production of biomass into useful biofuel products needs deep knowledge in chemistry, engineering, and control system. The types of bio-refineries based upon varieties of the raw materials, technologies, products, and processes are classified as first, second, and third-generation refineries (Rasslavicius et al., 2011). Some of the common technologies used for the conversion of biomass into biofuel and biogas are biological, physical, chemical, and thermal, depending on the type of product.

The biological conversion can be classified into anaerobic digestion, saccharification, and dark/photo fermentation, which tends to produce biomethane, ethanol, and biohydrogen, respectively (Nanda et al., 2014). Furthermore, the physical conversion can be classified into mechanical extraction, briquetting, and distillation. Bioconversion requires pretreatment and hydrolysis, which tends to release monomeric cellulose and hemicellulose for microbial fermentation. The thermochemical conversion can be classified into pyrolysis, liquefaction, and gasification to produce bio-oil, bio-crude oil and syngas, respectively (Okolie et al., 2021; Parakh et al., 2020).

1.3 BIOGAS PRODUCTION

Anaerobic digestion has traditionally aided low and middle-income countries, particularly the rural economies to sustainably manage the biogenic wastes, generate revenues and local employment while producing clean fuels to meet the domestic energy demands. The utilization of biogas is similar to the natural gas commonly used for cooking, heating or as a gaseous fuel for vehicles. Mainly, it contains CH₄, CO₂, water vapor and traces of N₂, NH₃, H₂, and H₂S. The energy content of biogas mainly depends upon the quantity of CH₄ present in it (Omer and Yemen, 2003). Hence, a high amount of CH₄ is always desirable. Care must be taken to avoid the water content and CO₂, and also to minimize the sulfur content for the engines of vehicles considering the pollution stage norms. The biogas has an average calorific value of 21–25 MJ/m³, while 1 m³ of biogas is equivalent to 0.5 L of diesel fuel with 6 kWh (FNR, 2009).

The biogas production rate of a plant depends upon the design, feedstock, temperature, and holding time (Martin et al., 2019). For example, the common feedstocks used in anaerobic digestion are cattle manure and agricultural residues. The biogas plants can be broadly be classified into two types such as fixed dome plants and floating gas-holder digester plants. Biogas is generally used for cooking by supplying the gas through pipes to households from the plant. Biogas has been effectively used as a fuel in industrial high compression spark-ignition engines. Biogas can be effectively used as fuel in water heaters by completely removing H₂S during the supply of the gas.

1.3.1 FIXED DOME BIOGAS DIGESTER PLANT

Generally, the structure of a biogas plant is composed of brick and cement having five components such as mixture tank, inlet tank, digester, outlet tank, overflow tank (Sims, 2007). The mixing tank is located above ground level, whereas the inlet tank is kept underground into an inclined chamber, and the inlet tank is opened just below the large digester tank. The ceiling of the tank is kept as a dome-shaped structure on which a long pipe is connected using an outlet valve for supplying the biogas. The digester opens from the bottom side of an outlet chamber,...