UPSC Prelims 2019 Q26: Environment & Ecology – Renewable Energy & Green Technologies
- (a) Extraction of rare earth elements
- (b) Natural gas extraction technologies
- (c) Hydrogen fuel - based automobiles
- (d) Waste - to - energy technologies
Answer: (d) Waste - to - energy technologies
Explanation
Pyrolysis and Plasma Gasification: Waste-to-Energy
| Technology | Mechanism | Product |
|---|---|---|
| Pyrolysis | Thermal decomposition of organic material in absence of oxygen at 300-900 C | Bio-oil, syngas, biochar - can be used for energy |
| Plasma Gasification | Uses plasma torch (10,000+ C) to break down waste at molecular level | Syngas (CO + H2 for electricity/fuel) and inert slag |
Both are advanced waste-to-energy technologies used to convert municipal solid waste, hazardous waste and biomass into usable energy while reducing landfill burden. Plasma gasification is more thorough (destroys toxins) but energy-intensive.
Answer: (d) Waste-to-energy technologies.
Why each option is right or wrong
- (a) Incorrect. Rare earth extraction uses solvent extraction and ion-exchange, not pyrolysis/plasma gasification.
- (b) Incorrect. Natural gas extraction uses drilling, hydraulic fracturing (fracking), not these techniques.
- (c) Incorrect. Hydrogen fuel cells use PEM/SOFC electrochemistry; hydrogen is produced by electrolysis or reforming, not pyrolysis/plasma gasification as a fuel-cell context.
- (d) CORRECT. Pyrolysis and plasma gasification are both waste-to-energy technologies converting MSW/biomass to syngas and other energy carriers.
Key point
Pyrolysis + Plasma Gasification = Waste-to-Energy (WtE). Pyrolysis = O2-free thermal decomposition. Plasma gasification = ultra-high-temp molecular breakdown -> syngas + inert slag.
Remember
Pyrolysis (thermal decomposition in absence of oxygen) and plasma gasification (ultra-high temperature molecular breakdown using plasma torch) are both waste-to-energy technologies that convert municipal solid waste, biomass and hazardous waste into syngas, bio-oil and other usable energy products while minimizing landfill.
Common mistakes
- Confusing pyrolysis (no oxygen) with incineration (full combustion with oxygen) or gasification (partial oxidation).
- Assuming plasma gasification produces electricity directly - it produces syngas, which is then used for power/fuel.
- Not knowing India's Swachh Bharat Mission Urban 2.0 promotes WtE plants for MSW management.
Exam tip
Thermal WtE hierarchy (by O2 content): Pyrolysis (0% O2) -> Gasification (partial O2) -> Incineration (full O2, complete combustion). Plasma gasification is the most advanced, capable of processing hazardous waste with minimal residuals.
Sources
- MNRE - Waste to Energy programme documentation
- NITI Aayog - Strategy for New India @75 (Solid waste management chapter)