UPSC Mains 2023 GS3 Q6: model answer
Discuss several ways in which microorganisms can help in meeting the current fuel shortage.
What the question wants
Ways microbes produce fuels: biogas, ethanol, biodiesel, hydrogen, microbial fuel cells.
How to structure it
Intro: fossil fuel dependence; microbes as biofactories. Body: (1) Biogas: methanogens in anaerobic digestion (GOBARdhan, SATAT CBG); (2) Bioethanol: yeast fermentation of sugarcane, molasses, grain; 2G ethanol from crop residue using enzymes (Panipat plant); (3) Biodiesel from algae; (4) Biohydrogen from bacteria and algae; (5) Microbial fuel cells; (6) Biobutanol. Conclusion: E20 target, energy security.
- 1(1) Biogas: methanogens in anaerobic digestion (GOBARdhan, SATAT CBG)
- 2(2) Bioethanol: yeast fermentation of sugarcane, molasses, grain
- 32G ethanol from crop residue using enzymes (Panipat plant)
- 4(3) Biodiesel from algae
- 5(4) Biohydrogen from bacteria and algae
- 6(5) Microbial fuel cells
- 7(6) Biobutanol
Model answer
India imports over 85% of its crude oil. Microorganisms can turn waste and biomass into fuels, easing this dependence.
- Methanogens: biogas
- Yeast: ethanol
- Enzymes: 2G ethanol from straw
- Microalgae: biodiesel
- Bacteria: biohydrogen
- Microbial fuel cells
- Biogas: methanogenic bacteria break down cattle dung and organic waste in the absence of oxygen to produce methane. GOBARdhan and the SATAT scheme promote compressed biogas.
- Bioethanol: yeast ferments sugar from sugarcane juice, molasses and grains into ethanol. India achieved 10% blending in 2022 and targets 20% (E20) by 2025-26.
- Second-generation ethanol: microbial enzymes break down crop residue such as rice straw; Indian Oil's Panipat 2G plant (2022) also reduces stubble burning.
- Algal biofuel: microalgae store oils that can be converted to biodiesel, and grow on wasteland or wastewater.
- Biohydrogen: some bacteria and algae release hydrogen during fermentation or photosynthesis.
- Microbial fuel cells: bacteria generate electricity while treating wastewater.
- Biobutanol from Clostridium bacteria.
Backed by the National Policy on Biofuels (2018), microbes can support energy security and cleaner air.
Keywords, cases and data to drop in
methanogens E20 2G ethanol algal biodiesel microbial fuel cell
Where most answers lose marks
- Listing biofuels without the microbial role.
- No Indian examples.
Fresh examples from current affairs
Agrivoltaics: Centre plans a scheme to push solar panels above farms; 5 GW seen in 3–4 years
MNRE Secretary Santosh Kumar Sarangi said on 19 October 2026 that the Centre is planning a central sector scheme to help States adopt agrivoltaics, either standalone or within PM-KUSUM 2.0. He expects capacity to cross 5 GW in three to four years if States notify feed-in tariffs. India hosts the 7th Agrivoltaics World Conference in New Delhi from 21 to 23 October.
UPSC angle: Prelims: agrivoltaics, PM-KUSUM components, feed-in tariffs. · Mains GS-III: energy transition and food security.
20 Oct 2026
Pumped storage hydropower: India’s roadmap for 100 GW of ‘water batteries’ by 2035-36
A PIB backgrounder of 19 October 2026 explains how pumped storage projects (PSPs) will store solar and wind power for India’s grid. India runs 7.43 GW of pumped storage today, is building 15.87 GW more and has an assessed potential of 345.38 GW. A roadmap aims to add about 100 GW between 2025-26 and 2035-36.
UPSC angle: Prelims: PSP types, CEA, ISTS waiver, IRENA ranking. · Mains GS-III: storage and the clean energy transition.
19 Oct 2026
Oil companies bar sugar-based ethanol for 2026-27; maize incentive cut to ₹2.79 a litre
The oil marketing companies have kept sugar out of India’s ethanol programme for the coming year. The tender issued on 16 October 2026 seeks about 11 billion litres of ethanol for the 2026-27 supply year, but asks for none made from sugarcane juice, sugar syrup or B-heavy molasses, because the Government wants sugar diversion for ethanol cut to zero. Grain must now carry the load, and even the maize incentive has been cut. Read this as a live example of the food-versus-fuel trade-off.
UPSC angle: Prelims: E20, NPB 2018, molasses grades, feedstocks. · Mains GS-III: energy security vs food security; farm incomes.
18 Oct 2026
Kufri Jamunia: ICAR-CPRI’s purple potato to fight hidden hunger
A PIB backgrounder of 18 October 2026 puts the spotlight on Kufri Jamunia, a purple-fleshed potato bred by ICAR’s Central Potato Research Institute and released in 2024. It has nearly twice the Vitamin C of a common potato and several times more zinc and iron, along with antioxidants called anthocyanins. The idea is clever: instead of asking people to change what they eat, make the food they already eat more nutritious. That is biofortification.
UPSC angle: Prelims: Kufri Jamunia, CPRI, anthocyanins, biofortification vs fortification. · Mains GS-III: nutrition security; GS-II: hunger.
18 Oct 2026Learn the concept
Question text as printed in the official UPSC question paper: https://www.upsc.gov.in/sites/default/files/QP-CSM-23-GENERAL-STUDIES-PAPER-III-180923.pdf The model answer is original Battle IAS work; use it to learn structure, not to memorise.