Which of the following can be used as feedstock for producing Sustainable Aviation Fuel?Agricultural

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UPSC Prelims is a competitive examination conducted in India. This question is from the 2024 UPSC Prelims Environment & Ecology paper.

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Question

Which of the following can be used as feedstock for producing Sustainable Aviation Fuel?Agricultural residuesCorn grainWastewater treatment sludgeWood mill waste

Accepted Answer

Correct Answer: C — 1, 2, 3 and 4Step-by-step Solution:Sustainable Aviation Fuel (SAF) is a liquid fuel used in commercial aviation that significantly reduces CO₂ lifecycle emissions compared to conventional jet fuel (up to 80% reduction). It is produced from non-petroleum renewable feedstocks.Item 1 — Agricultural residues: SAF feedstock. ✓ Crop residues like rice straw, wheat stubble, corn stover, sugarcane bagasse — collectively called lignocellulosic biomass — can be processed through biochemical (fermentation) or thermochemical (gasification, pyrolysis) pathways to produce bio-jet fuel.Item 2 — Corn grain: SAF feedstock. ✓ Corn grain (starch) is a well-established biofuel feedstock. First-generation biofuel (corn ethanol) is produced from corn starch via fermentation; Alcohol-to-Jet (ATJ) technology can further convert ethanol to SAF. The US Department of Energy estimates ~1 billion dry tons of biomass can be sustainably collected annually in the USA, including corn grain.Item 3 — Wastewater treatment sludge: SAF feedstock. ✓ Municipal wastewater treatment sludge (biosolids) is classified as a 'wet waste' feedstock for SAF production. Biogas (methane) can be captured from sludge digestion and further processed into SAF, or sludge can be hydrothermally liquefied directly into bio-crude.Item 4 — Wood mill waste: SAF feedstock. ✓ Forestry residues and wood processing waste (sawdust, wood chips, bark) are lignocellulosic feedstocks for SAF. They can be processed via gasification (syngas → Fischer-Tropsch synthesis → jet fuel) or pyrolysis pathways.All four are valid SAF feedstocks.Why other options are incorrect:Options A, B, D: All undercount — every item listed can be used as SAF feedstock.Key Concept: Sustainable Aviation Fuel (SAF): Definition: Renewable jet fuel from non-petroleum sources; Lifecycle CO₂ reduction: Up to 80% vs conventional jet fuel; ASTM D7566 certified for blending with conventional jet fuel (up to 50% blend). SAF production pathways (ASTM approved): HEFA (Hydroprocessed Esters and Fatty Acids) — from used cooking oil, animal fats, vegetable oils; ATJ (Alcohol-to-Jet) — from ethanol/isobutanol (sugarcane, corn, cellulosic biomass); FT (Fischer-Tropsch) — from woody biomass, MSW via gasification; SIP (Synthesized Iso-Paraffins) — from sugar via fermentation; DSHC (Direct Sugar to Hydrocarbons); Co-processing in petroleum refineries. SAF global targets: ICAO (International Civil Aviation Organization) — net zero carbon by 2050; EU: 2% SAF mandate from 2025, rising to 70% by 2050 (ReFuelEU Aviation). India's SAF plans: Indian Oil Corporation (IOC) and others developing SAF from used cooking oil and agricultural residues; Ministry of Civil Aviation SAF Roadmap. Airlines using SAF: Air India, IndiGo among Indian airlines exploring SAF blending.

Which of the following can be used as feedstock for producing Sustainable Aviation Fuel?Agricultural residuesCorn grainWastewater treatment sludgeWood mill waste

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Which of the following can be used as feedstock for producing Sustainable Aviation Fuel?Agricultural residuesCorn grainWastewater treatment sludgeWood mill waste

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