Detailed Explanation:

Answer: Option 4 — Waste-to-energy technologies

Pyrolysis and plasma gasification are advanced thermochemical waste-to-energy technologies that convert waste materials into useful energy products. Pyrolysis involves heating organic waste in an oxygen-deficient environment to produce syngas, bio-oil, and char, while plasma gasification uses extremely high temperatures (created by plasma torches) to break down waste into syngas rich in hydrogen and carbon monoxide. Both processes offer sustainable solutions for waste management while generating energy, making them key technologies in the circular economy framework.

📝 Short Notes: Waste-to-Energy Technologies

• Pyrolysis: Thermal decomposition of organic materials at 300-900°C in the absence of oxygen, producing syngas, bio-oil, and biochar. Used for plastic waste, biomass, and municipal solid waste treatment.
• Plasma Gasification: Uses plasma torches creating temperatures above 3000°C to convert waste into syngas and inert slag. Can process hazardous and mixed waste streams effectively.
• Products: Syngas (mixture of H₂, CO, CH₄) can be used for electricity generation, as chemical feedstock, or converted to liquid fuels.
• Advantages: Significant waste volume reduction (up to 90%), minimal landfill requirement, energy recovery, and reduced greenhouse gas emissions compared to conventional incineration.
• Applications in India: Several pilot projects and commercial plants are being explored under Swachh Bharat Mission and Smart Cities initiatives for sustainable waste management.