Biogas – Composition, Advantages, Disadvantages, and Applications

Biogas: Biogas is a renewable and environmentally harmless energy source. The organic materials,like food scraps and animal manure, that gets decomposed produces biogas. Through the action of microorganisms, these materials are broken down without oxygen. This is called anaerobic digestion. A mixture of gases produced by this digestion, mostly carbon dioxide and methane, can be used as an energy source.

Biogas – Comprehensive Understanding of Biogas

Energy can transform into several forms. How may Is there any way to use energy released during the decomposition of biological materials?

Depending on the air and environmental conditions available, an organic material can either undergo aerobic or anaerobic digestion during its breakdown process.

Anaerobic means that organic matter breaks down without availability of oxygen, whereas aerobic means that organic matter breaks down in the presence of oxygen. Both processes are entirely different from one another, Also separate bacterial populations perform the various digesting stages and produce the various final products. The energy released during the biodegradation of organic waste can be transformed and captured into a valuable commodity.

The aerobic digestion of organic material done in a controlled environment can provide us with a nutrient-rich fertilizer known as compost Anaerobic digestion can also result in the creation of biogas, which is a very helpful energy source.

Biogasenergy can be produced from replenishable organic resources, making it a renewable energy source. Burning biogas emits fewer greenhouse gases than conventional fossil fuels. This makes it a cleaner fuel substitute. Biogas can be used for cooking, heating, and generating electricity.

Biogas Composition

Biogas is made from a natural process taking place in a sealed environment. Hence, it is composed of carbon dioxide, methane and some nitrogen. The most common ratio is 40% carbon dioxide (CO2) and 60% methane (CH4). Usually, biogas contains carbon dioxide from 55 to 25% and methane in a proportion of 45 to 75%.

Biogas Advantages

Producing and using biogas energy has advantages and disadvantages. Before investing in a bio gas plant, it is advisable to analyse the practical aspects of biogas.

The most popular advantages of biogas are:

• Biogas does not release carbon into the atmosphere. This makes it a clean, renewable energy source that operates on a carbon-neutral method.

• It helps divert food waste from landfills, positively impacting the environment and economics.

• It reduces water and soil contamination from human faeces and animal manure, maintaining a healthy and safe environment for many communities worldwide.

• It reduces the amount of CH4 (methane) emitted to the atmosphere, countering climate change with a possible immediate environmental impact.

Biogas: Disadvantages

1. Biogas generation is also affected by changes of the weather. The ideal temperature for bacteria needed to digest waste is around 37°C. It is difficult in cold climates, as digesters require heat energy to maintain a constant biogas supply.
2. After refinement and compression, biogas still contains impurities and generated bio-fuel was used to power automobiles, it could corrode the engine’s metal parts, which may lead to maintenance costs.
3. It is difficult for big-scale production to meet a huge population’s needs. Bio gas technology must be more efficient. Currently, there are no new biogas technologies present that can streamline the process and make it more accessible and affordable.
4. It is challenging to completely depend on biogasenergy as biogas can’t be controlled completely. This is because the production of biogas depends on a biological process. Also, Biogas isn’t accessible equally worldwide as it works better in warm climates.
5. Many governments are not very willing to invest in the sector, although today, bio gas plant can cover some energy needs.
6. Biogas generation is much more suitable for rural and suburban areas as industrial bio gasplant need plentiful supply of raw materials.

Steps involved in obtaining biogas

• Hydrolysis

This is the first step towards biogasproduction. It is critical process because the higher the breakdown of complex matter, the more available substrate for biogas production. The hydrolysis process breaks down the organic macromolecule into smaller compounds.

In this process, the hydrolytic bacteria secrete extracellular enzymes like protease, cellulose, amylase, and lipase that break down carbohydrates into simple sugars like disaccharides and monosaccharides. Lipids are converted to various chains of fatty acids while proteins are converted to amino acids.

For hydrolysis, 6 to 7 pH and a 30 to 50 C temperature range is ideal.

• Acidogenesis

The hydrolysis step provides small molecular compounds as its final product that can pass through the cell membrane of acidogenic bacteria.

The acidogenic bacteria convert precursor compounds into intermediary compounds, which is known as volatile fatty acids (VFAs), alcohols like ethanol, methanol, and aldehydes, and CO2.

VFA consists of organic acids such as acetates and larger organic acids like butyrate, propionate, and pentanoate in varying proportions.

• Acetogenesis

Acetate is used directly as a substrate for methanogenesis. With higher organic acids, this is different.

Acetogenesis process, higher organic acids like butyrate and propionate are converted to hydrogen and acetates by acetoclastic bacteria.

Hydrogen production is around 11% from the acetogenesis process, while acetates is around 25%.

• Methanogenesis

The final step of anaerobic digestion is the Methanogenesis process. The methanogenic bacteria convert the intermediates from previous steps, like methanol, hydrogen, acetates, and methylamine, into H2O and methane.

Acetoclastic methanogens consumed Acetate and converted to methane. Using hydrogen to produce methane, another set of hydrogenotrophic methanogens reduces CO2 during the acetogenesis step and converts it into methane.

At a higher pH process of methanogenesis takes place. 2/3 of the methane produced is generated through acetoclastic methanogenesis, while 1/3 is generated through hydrogenotrophic methanogenesis.

Application of Biogas

• Rural areas mostly use biogas as cooking gas.
• It can be used for the production of electricity.
• It can be used in instruments for water heating, space (room) heating etc.
• It can replace compressed natural gas for use in automobiles.
• Carbon dioxide in on-site CHP facilities can be replaced by it.
• It is used in transport.
• Production of biogas produces a dry solid byproduct, which is used as manure which is used in many ways.
• It is used in many states for street lighting purposes.
• It can be used in hydrogen fuel cells as well.

FAQs on Biogas

What is biogas?

Biogas is a biological decomposition process of organic materials without oxygen, such as poultry droppings, cow dung, etc. Biogas is also called anaerobic digestion.

What is the composition of biogas?

The composition of biogas is carbon dioxide (CO2) 35-40%, methane (CH4) 55-60%, trace elements of ammonia hydrogen sulphide (H2S), and moisture.

What are the uses of biogas?

Biogas are used for running engines, cooking, and lighting.

What is the bio gas plant?

A bio gas plant is a establishment that offers oxygen-free environment where anaerobic digestion can occur