Maarg Manthan · Topic 12.4

Biofuels and Biogas

Environment & Ecology › Energy Resources · Topic 12.4

Biofuels are fuels made from biological material (biomass) such as crops, crop residues, oils, animal waste and municipal waste. Liquid biofuels include bioethanol, made by fermenting sugars from sugarcane juice, molasses, grains or cellulosic material and blended with petrol, and biodiesel, made from vegetable oils, used cooking oil or animal fat and blended with diesel. They are grouped into first generation fuels from food crops, second generation fuels from non-food biomass such as straw and bagasse, third generation fuels from algae, and sometimes fourth generation from engineered organisms. Biogas is a gas mixture, about 55 to 65 percent methane and 30 to 40 percent carbon dioxide, produced when bacteria break down organic matter such as cattle dung, crop residues, food waste and sewage in the absence of oxygen, a process called anaerobic digestion. It is used for cooking, lighting and power, and the leftover slurry is a rich manure. Compressed biogas (CBG) can replace CNG.

5 min read · UPSC Prelims · Environment & Ecology · Energy Resources

At a Glance

Liquid fuels Ethanol, biodiesel
Generations First to fourth
Biogas Methane 55 to 65 percent
Process Anaerobic digestion
Schemes GOBARdhan, SATAT
Exam link UPSC Prelims, Environment & Ecology: Energy Resources

Where Does It Fit?

This topic follows fuel cells and moves to fuels from biomass. It prepares for the policy topics on the National Policy on Biofuels and renewable energy. Previous topic: Fuel Cells and Microbial Fuel Cells. Next topic: Geothermal Energy and Solar Energy.

What Are the Generations of Biofuels?

Generation	Feedstock and examples
First generation	Food crops: ethanol from sugarcane juice, molasses, maize and rice; biodiesel from edible oils; raises food versus fuel concerns
Second generation	Non-food biomass: crop residue, straw, bagasse, forest and municipal waste, non-edible oilseeds like jatropha and karanja; cellulosic ethanol
Third generation	Algae grown in ponds or reactors for oil and ethanol
Fourth generation	Engineered microbes and crops that capture more carbon
Bioethanol	Fermented alcohol blended with petrol, such as E10 and E20
Biodiesel	Esters from oils and fats made by transesterification
Biogas and CBG	Gas from anaerobic digestion, purified into compressed biogas

How Is Biogas Made and Used?

Feedstock: cattle dung, poultry waste, food waste, crop residue, sewage sludge and press mud
Digester: a sealed tank where bacteria produce biogas without oxygen
Stages: hydrolysis, acid formation, acetic acid formation and methane formation
Composition: about 55 to 65 percent methane, 30 to 40 percent carbon dioxide and traces of hydrogen sulphide
Uses: cooking, lighting, electricity, and after purification, vehicle fuel
Slurry: the digested slurry is a nutrient-rich organic manure
Plant types: floating drum (KVIC) and fixed dome (Deenbandhu) designs
Benefits: clean cooking, waste management, less deforestation and lower methane emissions

What Else Should You Remember?

Bioethanol blending: India has been raising ethanol blending in petrol, with 10 percent reached in 2022 and a target of 20 percent by 2025 to 2026; check the latest
Biodiesel blending: a target of 5 percent biodiesel in diesel has been set under the policy
Jatropha: a non-edible oilseed shrub tried for biodiesel with mixed results
Used cooking oil: collected and converted into biodiesel under the RUCO scheme
Molasses: by-product of sugar making and a major ethanol feedstock
Flex fuel: vehicles able to run on high ethanol blends
Food versus fuel: using food crops for fuel can raise food prices and use land and water
Second generation plants: cellulosic ethanol plants using rice straw, for example at Panipat, Haryana
Stubble burning link: using paddy straw for fuel or CBG can reduce field burning
GOBARdhan: Galvanizing Organic Bio-Agro Resources Dhan, launched in 2018 to convert cattle dung and waste into biogas and manure
SATAT: Sustainable Alternative Towards Affordable Transportation, launched in 2018 to set up compressed biogas plants
National Biogas and Organic Manure Programme: supports family-size biogas plants
Gobar gas: popular name for cattle dung biogas in India
Anaerobic digestion: breakdown of organic matter by microbes in the absence of oxygen
Methanogens: archaea that produce methane in the last stage
Hydrogen sulphide: a corrosive trace gas that is removed before use
Biomethane: purified biogas with over 90 percent methane
Carbon neutrality: biofuel carbon was recently taken from the air, but cultivation and processing still cause emissions
Land and water: energy crops can compete for land and water
Economic benefits: rural jobs and extra income for farmers
Link to previous: see Fuel Cells and Microbial Fuel Cells
Link to next: see Geothermal Energy and Solar Energy
Link to policy: see National Policy on Biofuels
Caution: blending levels and targets are revised often, so check the latest policy notifications
Exam hint: remember the generation examples and the composition of biogas
Cow dung in India: India has a very large cattle population, so dung is a big feedstock for biogas
Biogas slurry: the slurry has nitrogen, phosphorus and potassium and improves soil, so it replaces some chemical fertiliser
Bagasse: fibrous sugarcane residue used to make power and second generation ethanol
Energy crop concerns: growing crops only for fuel can raise land and water demand and affect food prices
Algal biofuel: algae can grow fast on non-farm land and in waste water, but cost remains high

Why Does It Matter for the Exam?

Biogas methane: 55 to 65 percent
Process: Anaerobic digestion
2G feedstock: Non-food biomass
Current affairs link: E20 and CBG
Common errors: listing algae as second generation or biogas as mostly carbon dioxide

As an analytical point, biofuels can cut oil imports, farm waste and emissions, but crop-based fuels compete with food and water. Waste-based second generation fuels and biogas fit better with sustainable development.

Why Is This Topic Important?

Source Biomass
Gain Waste to energy
Risk Food versus fuel

What Came Next?

The next topic covers geothermal energy and solar energy. Next topic: Geothermal Energy and Solar Energy.

Key People and Terms

Bioethanol Alcohol fuel
Biodiesel Oil-based diesel substitute
Anaerobic digestion Oxygen-free breakdown
CBG Compressed biogas
2G biofuel Fuel from non-food biomass
Transesterification Biodiesel making reaction

Exam Corner

Points to Remember

Biogas has 55 to 65 percent methane.
Process: anaerobic.
Second generation: non-food.
GOBARdhan: 2018.
SATAT: 2018.

Do Not Confuse With

Ethanol and biodiesel Petrol blend versus diesel blend
1G and 2G biofuel Food crops versus non-food biomass
Biogas and CBG Raw gas versus purified compressed gas

Memory Hook

Sugar to ethanol, oil to diesel, dung without air gives methane.

Mains Angle

Questions ask for generations and biogas. These points help.

Types Generations
Gain Waste use
Risk Food versus fuel

A Question You May Face

An original practice question, not a past paper question.

“Discuss the types of biofuels and the potential of biogas in India. What are the concerns about food versus fuel?”

How to Answer

Types Generations.
Biogas Digestion.
Schemes GOBARdhan.
Risk Food.

GS Relevance

Prelims: generations, feedstock, biogas composition. GS Paper 3: bioenergy and waste-to-energy.

Frequently Asked Questions

What are biofuels?

Biofuels are fuels made from biomass such as crops, residues, oils, animal waste and municipal waste. The main liquid biofuels are bioethanol, blended with petrol, and biodiesel, blended with diesel. Gaseous biofuels include biogas, made from organic waste. They can reduce fossil fuel use and, if sustainably produced, greenhouse gas emissions.

What are the generations of biofuels?

First generation biofuels come from food crops like sugarcane, maize and edible oils. Second generation biofuels come from non-food biomass such as straw, bagasse and wood. Third generation biofuels use algae, and fourth generation uses genetically engineered organisms. Later generations aim to avoid competing with food.

How is biogas produced and what is its composition?

Biogas is produced by anaerobic digestion, in which bacteria break down organic matter such as cattle dung, food waste and crop residue in a sealed digester without oxygen. The gas contains about 55 to 65 percent methane and 30 to 40 percent carbon dioxide, with traces of hydrogen sulphide. The leftover slurry is a good organic manure.

What is the GOBARdhan scheme?

GOBARdhan, launched in 2018, stands for Galvanizing Organic Bio-Agro Resources Dhan. It promotes converting cattle dung, crop residue and other organic waste into biogas, compressed biogas and organic manure, to keep villages clean, create income for farmers and provide clean energy.

What is the SATAT initiative?

SATAT, Sustainable Alternative Towards Affordable Transportation, was launched in 2018 by the Ministry of Petroleum and Natural Gas to encourage entrepreneurs to set up compressed biogas plants and supply CBG to oil marketing companies for use as an automotive and industrial fuel in place of CNG.

PYQ Practice — Statement Analysis

1 Biogas is mainly methane and carbon dioxide.

True

About 55 to 65 percent methane.

2 Biogas is produced in the presence of oxygen.

False

It is produced anaerobically.

3 Second generation biofuels use non-food biomass.