Revision summary
Yeasts and 2G microbes make ethanol; India blends it under the Ethanol Blended Petrol programme toward E20. Indian Oil’s Panipat 2G plant and Numaligarh’s bamboo bio-refinery are real second-generation sites. Anaerobic bacteria make biogas; SATAT and GOBARdhan upgrade it to transport and village fuel. Algal biodiesel and microbial hydrogen exist in CSIR and institute pilots, not as large national supply. These routes cut a slice of the oil shortage only with real plants and disciplined feedstock.
Model answer
Copper italics in this answer — like this — are the key facts. Each one is unpacked in the Facts & figures rail.
Introduction
India still imports most of its crude oil. Microbes cannot replace every barrel. They can make alcohol, methane, lipids and hydrogen from sugar, dung, residue and algae, which cuts a slice of the shortage and the import bill if plants actually run.
Body
Bioethanol
- Yeasts such as Saccharomyces ferment sugarcane molasses and grain starch to ethanol; bacteria and fungi are used in second-generation processes that break rice-straw and other cellulose.
- India blends ethanol in petrol under the Ethanol Blended Petrol programme, with an E20 (20 per cent) target.
- First-generation supply is molasses and surplus grain. Second-generation plants exist at scale in a few places, including Indian Oil’s 2G ethanol plant at Panipat and the Numaligarh bamboo-based bio-refinery in Assam; other oil-company 2G units have been under construction rather than all online.
Biogas and compressed biogas
- Anaerobic bacteria in digesters turn cattle dung, press-mud and urban wet waste into methane-rich biogas.
- Upgraded gas is Compressed Bio Gas, sold as a transport fuel under Sustainable Alternative Towards Affordable Transportation (SATAT) with oil marketing companies as off-takers.
- GOBARdhan supports village and cluster plants. This is a working rural fuel, not a laboratory story.
Algal biodiesel
- Microalgae can store lipids that are transesterified to biodiesel and can grow on non-arable water bodies.
- Indian work sits mainly in CSIR, DBT and IIT pilots. Commercial algal diesel is not a large operating source of national fuel yet; it is a research path with high harvest cost.
Microbial hydrogen
- Some bacteria and cyanobacteria make hydrogen by dark fermentation or photolysis of water.
- This remains pilot-scale. India’s hydrogen mission is still dominated by electrolysis and industrial by-product gas, not by microbial farms.
Meeting the shortage
- The honest contribution today is ethanol blending and SATAT biogas. Algae and microbial hydrogen are future options.
- They help only with feedstock discipline: food-versus-fuel for grain ethanol, and residue collection for 2G, must stay explicit.
Flow diagram
Conclusion
Microbes already add ethanol and biogas to India’s fuel mix through EBP, Panipat-type 2G plants, Numaligarh, SATAT and GOBARdhan. Algal biodiesel and microbial hydrogen are real science, not yet national supply. They ease shortage only where plants run and feedstock is honest.
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Next question on this syllabus topic (2023 · Q7). View answer →
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Can microbes end India’s oil imports?
No. They substitute a share of petrol and some gas. Crude for diesel, aviation and chemicals still dominates.
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Is algal biodiesel already a commercial Indian fuel?
Not at national scale. It is laboratory and pilot work; harvest cost is still high.
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