UPSC CSE Prelims
Bioenergy Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 3 — 1, 2, 3 and 4

All four materials listed can serve as feedstock for producing Sustainable Aviation Fuel (SAF). Agricultural residues and wood mill waste are lignocellulosic biomass sources that can be converted through thermochemical or biochemical processes. Corn grain provides fermentable sugars for ethanol production, which can be upgraded to SAF. Wastewater treatment sludge, rich in organic matter, can undergo anaerobic digestion to produce biogas, subsequently convertible to SAF.

✅ Statement 1 – Correct: Agricultural residues (crop stalks, husks, leaves) are viable lignocellulosic biomass sources for SAF production through various conversion pathways.
✅ Statement 2 – Correct: Corn grain contains fermentable sugars that can be converted to ethanol and further processed into SAF via alcohol-to-jet fuel pathways.
✅ Statement 3 – Correct: Wastewater treatment sludge is rich in organic matter and can be converted to biogas through anaerobic digestion, which can then be upgraded to SAF.
✅ Statement 4 – Correct: Wood mill waste (sawdust, wood chips, bark) is a lignocellulosic material convertible to SAF through gasification, pyrolysis, or other thermochemical processes.

📝 Short Notes: Sustainable Aviation Fuel (SAF)

• Definition: SAF is a drop-in replacement for conventional jet fuel, produced from sustainable feedstocks, reducing lifecycle carbon emissions by up to 80%.
• Feedstock Categories: Includes agricultural residues, forestry waste, municipal solid waste, industrial waste, algae, and dedicated energy crops.
• Production Pathways: Major technologies include Fischer-Tropsch synthesis, Hydroprocessed Esters and Fatty Acids (HEFA), Alcohol-to-Jet (ATJ), and gasification.
• Certification: SAF must meet ASTM D7566 standards and can be blended with conventional jet fuel up to 50% (some pathways allow 100%).
• Global Initiatives: ICAO's CORSIA scheme, EU's ReFuelEU Aviation, and US SAF Grand Challenge aim to scale SAF production and adoption.
• Indian Context: India is exploring SAF production from agricultural waste, used cooking oil, and other biomass sources to decarbonize aviation sector.