Biogas

Introduction

Biogas is a renewable and clean gaseous fuel produced through the anaerobic decomposition (decomposition in the absence of oxygen) of organic matter by microorganisms. It is primarily composed of methane (CH₄) and carbon dioxide (CO₂), along with small amounts of hydrogen sulphide, hydrogen, nitrogen and water vapour.

Biogas is an important component of the circular economy, as it converts organic waste into clean energy while producing nutrient-rich organic manure as a by-product. It contributes to energy security, waste management, climate change mitigation and sustainable agriculture.

Raw Materials (Feedstock)

Biogas can be produced from a wide range of biodegradable materials, including:

• Cattle dung
• Agricultural residues
• Food waste
• Kitchen waste
• Poultry litter
• Animal manure
• Sewage sludge
• Municipal organic waste
• Industrial organic effluents

Process of Biogas Production

Biogas is produced through Anaerobic Digestion (AD), which occurs in a closed chamber called a biogas digester.

Stages of Anaerobic Digestion

1. Hydrolysis
   • Complex organic matter (carbohydrates, proteins and fats) is broken into simpler compounds.
2. Acidogenesis
   • Simple compounds are converted into volatile fatty acids, alcohols and hydrogen.
3. Acetogenesis
   • Volatile fatty acids are converted into acetic acid, hydrogen and carbon dioxide.
4. Methanogenesis
   • Methanogenic microorganisms convert acetic acid and hydrogen into methane, producing biogas.

Composition of Biogas

Typical composition includes:

• Methane (CH₄): 50–75%
• Carbon dioxide (CO₂): 25–50%
• Hydrogen sulphide (H₂S): Trace amounts
• Water vapour: Variable
• Hydrogen and Nitrogen: Small quantities

Methane is the combustible component responsible for the energy value of biogas.

Types of Biogas Plants

Fixed-Dome Plant

• Underground dome-shaped structure.
• Low maintenance.
• Long operational life.
• Widely used in rural areas.

Floating-Drum Plant

• Gas is collected in a movable steel or plastic drum.
• Easy to monitor gas production.
• Requires relatively higher maintenance.

Plug-Flow Digester

• Suitable for large livestock farms.
• Feedstock moves continuously through the digester.

Balloon/Flexible Digester

• Made from flexible plastic or rubber.
• Low-cost and easy to install.
• Suitable for small-scale applications.

Upgraded Biogas (Compressed Biogas)

Raw biogas can be purified by removing carbon dioxide, hydrogen sulphide and moisture to produce Compressed Biogas (CBG) or Bio-CNG, which contains over 90% methane.

CBG has properties similar to Compressed Natural Gas (CNG) and can be used as a transport fuel or injected into gas distribution networks.

Applications

Domestic Use

• Cooking fuel.
• Water heating.
• Lighting (with suitable burners).

Electricity Generation

• Fuel for gas engines and generators.
• Decentralised rural power generation.

Transport

• Compressed Biogas (CBG) as an alternative to CNG.
• Fuel for buses, cars and commercial vehicles.

Industrial Use

• Boilers.
• Furnaces.
• Combined heat and power (CHP) plants.

Agriculture

• Digested slurry is used as organic manure, improving soil fertility and reducing dependence on chemical fertilisers.

Challenges

• High initial installation cost.
• Irregular availability and collection of feedstock.
• Technical maintenance issues.
• Limited awareness among users.
• Leakage of methane if plants are poorly maintained.
• Difficulty in scaling up decentralised projects.
• Need for efficient collection and segregation of biodegradable waste.

Government Initiatives

National Bioenergy Programme (NBP)

Implemented by the Ministry of New and Renewable Energy (MNRE), the programme promotes biogas, biomass and waste-to-energy projects through financial assistance.

Sustainable Alternative Towards Affordable Transportation (SATAT)

Launched in 2018 by the Ministry of Petroleum and Natural Gas, SATAT aims to establish a nationwide ecosystem for the production and use of Compressed Biogas (CBG) from agricultural residues, cattle dung and organic waste.

Objectives include:

• Reducing dependence on imported fossil fuels.
• Providing additional income to farmers.
• Managing agricultural residues.
• Promoting clean transport fuels.

GOBARdhan Scheme

Galvanizing Organic Bio-Agro Resources Dhan (GOBARdhan) was launched in 2018 under the Swachh Bharat Mission (Grameen).

It promotes:

• Scientific management of cattle dung and organic waste.
• Community biogas plants.
• Production of compressed biogas and bio-slurry.
• Circular economy in rural areas.

Waste-to-Wealth Initiatives

Several urban local bodies promote biogas plants for processing municipal organic waste under Swachh Bharat Mission (Urban) and other waste management programmes.

Significance for India

Biogas contributes to:

• Energy security by diversifying the energy mix.
• Climate commitments under India’s Nationally Determined Contributions (NDCs).
• Net Zero target by 2070 through reduced greenhouse gas emissions.
• Doubling farmers’ income through sale of agricultural residues and organic manure.
• Swachh Bharat Mission through scientific waste management.
• Atmanirbhar Bharat by reducing dependence on imported natural gas and petroleum products.

Way Forward

• Expand decentralised biogas and CBG plants in rural and urban areas.
• Improve segregation and collection of biodegradable waste.
• Strengthen financial incentives and access to credit.
• Promote public-private partnerships for commercial-scale CBG production.
• Enhance research on efficient anaerobic digestion technologies.
• Develop robust supply chains for feedstock and bio-slurry marketing.
• Increase awareness and technical training for plant operators.
• Integrate biogas production with municipal solid waste and agricultural residue management.

Conclusion

Biogas is a sustainable, renewable and environment-friendly source of energy that simultaneously addresses energy generation, waste management, climate change and rural development. With initiatives such as SATAT, GOBARdhan and the National Bioenergy Programme, India is promoting biogas as a key component of its clean energy transition and circular economy. Expanding biogas production will strengthen energy security, improve sanitation, enhance farmers’ incomes and contribute to achieving the country’s long-term climate and sustainable development goals.