Possible UPSC Questions
- Critically examine whether first- and second-generation biofuels can ensure net reductions in radiative forcing.
- Discuss the constitutional and policy framework that governs bio-ethanol production in India.
- Analyse the food-versus-fuel debate in the context of India’s 20 % ethanol-blending target.
- Explain the environmental externalities associated with large-scale biofuel cultivation.
Quick Outline of Key Facts
| Parameter | Details |
| Global biomass flow | ≈ 250 Gt dry matter/yr → 100 Gt C fixed; photosynthesis captures 2 × 10²¹ J yr⁻¹ |
| Ethanol categories | 1G – sugary/starchy crops (cane, corn); 2G – lignocellulosic waste (bagasse, husk) |
| Steps in 2G ethanol | Pretreatment → enzymatic saccharification → fermentation → distillation & dehydration |
| Energy density | Ethanol 24 GJ m³⁻¹ vs petrol 39 GJ m³⁻¹; blends E5–E15 usable in standard SI engines |
| Top producers (2024) | USA > 16 bn gal; Brazil (cane); India > 1 bn gal (~5 % world output) |
| India targets | E20 by 2025-26; feedstock from cane juice, B/C-molasses, surplus rice via FCI |
| GHG profiles | Cane ethanol can be net-negative; corn & many 2G routes marginal or positive when LUC/N₂O factored |
| Ecological risks | Land-use change (Amazon clearing), monoculture, water stress, N₂O & CH₄ emissions |
Summary
Biofuels, especially bio-ethanol, are championed worldwide as a pathway to decarbonise transport and cushion economies against oil volatility. Ethanol is produced via anaerobic microbial fermentation of plant sugars: first-generation (1G) routes rely on food-grade feedstocks such as sugarcane, beet, maize or rice, whereas second-generation (2G) technologies attempt to unlock fermentable sugars from lignocellulosic “waste” like bagasse, straw and wood. Global photosynthesis fixes about 100 Gt of carbon annually; redirecting a fraction of this existing flux to human energy use, in principle, avoids introducing “new” fossil carbon into the atmosphere.
Technically, ethanol’s combustion qualities—high octane, anti-knock behaviour, liquid range from –114 °C to 78 °C—allow blends up to E15 in conventional spark-ignition engines with minor tuning. Yet its volumetric energy density is 40 % lower than petrol, so comparable range demands higher volumes. Fermentation processes also face biochemical ceilings: ethanol above 10 % kills yeasts, necessitating energy-intensive distillation; cellulase enzymes that convert cellulose to glucose are slow, unstable and costly. Pretreatment of crop residues often uses corrosive chemicals, pushing up 2G production costs.
From a systems perspective, biofuels are no panacea. Sugarcane ethanol (Brazilian model) can achieve net-negative greenhouse-gas footprints due to cogeneration with bagasse and circular use of by-products. Most other pathways fare worse once indirect land-use change, fertiliser-derived N₂O and methane from residue decomposition are tallied. Large-scale diversion of maize to US ethanol and India’s growing grain-based programme raise food-security concerns, especially for low-income populations. Ecologically, converting forests or wetlands to energy monocultures erodes biodiversity, accelerates freshwater depletion and can even heighten radiative forcing if pristine carbon sinks are lost.
India, now the world’s third-largest ethanol producer, plans 20 % blending by 2025-26 and has authorised use of cane juice, B/C molasses and 2.3 Mt of surplus FCI rice. While promoting rural income and import substitution, policymakers must weigh hidden costs: pretreatment energy, water footprints, displacement of feed grain markets and potential genetic-modified (GM) maize imports. Achieving true carbon abatement will require life-cycle accounting, robust sustainability criteria, investment in enzyme/immobilised-bioreactor research and parallel electrification of transport.
Significance to the UPSC Exam
- Environment & Ecology (GS III): Illustrates carbon cycle, radiative forcing, life-cycle emissions, land-use change.
- Economy & Agriculture (GS III): Links ethanol policy to food security, MSP grains, import dependence.
- Science & Tech: Explains biochemical engineering, cellulase constraints, 1G vs 2G technologies.
Energy Security & Policy: Provides data for answers on India’s E20 roadmap, National Biofuel Policy, Global Biofuels Alliance.
Incorporating these multidimensional aspects strengthens analytical answers in mains as well as prelims MCQs on renewable energy and climate change.
