Solid Waste

**Statement 1 is incorrect:** The bio-toilets actually utilize bacteria, not fungi, to decompose human waste. These bacteria are anaerobic, meaning they function in an oxygen-free environment within the bio-digester tank. **Statement 2 is incorrect:** The end products of decomposition in the bio-toilets are not just ammonia and water vapor. The process generates a combination of: * **Treated water:** This water undergoes chlorination before being released. * **Methane:** This gas is released in small amounts and vents into the atmosphere. * **Sludge:** A minimal amount of solid residue remains after decomposition. Therefore, the correct answer is None of the above.

**Statement 1 is correct:** Fly ash finds various applications in construction, including brick manufacturing. Its pozzolanic properties improve the strength and durability of bricks. **Statement 2 is correct:** Fly ash can partially replace Portland cement in concrete mixes. It reacts with the hydration byproducts of cement to form additional cementitious materials, leading to benefits like improved workability, reduced heat of hydration, and enhanced concrete performance. **Statement 3 is incorrect:** Fly ash primarily consists of silicon dioxide (SiO2), aluminum oxide (Al2O3), and calcium oxide (CaO). However, it may also contain trace amounts of heavy metals like arsenic, mercury, and chromium.

A circular economy focuses on minimizing waste, reusing resources, and improving efficiency, all of which help lower greenhouse gas emissions and conserve raw materials. ✅ **Statement I: Correct** By **reducing waste and energy use**, the circular economy helps **cut greenhouse gas emissions**. ✅ **Statement II: Correct** It **reduces the need for raw materials** through **reuse, recycling, and product life extension**. ✅ **Statement III: Correct** It also **lowers production waste** using efficient and sustainable design and processes.