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Correct Answer: (d) 1, 2 and 3

Explanation:

Steel slag, a by-product of steel production, is utilized in multiple sectors due to its physical and chemical properties. Here's the analysis of the given options:

• Construction of Base Road

1. 1. • Steel slag is widely used as an aggregate in road construction due to its high density and durability. It enhances road strength and reduces reliance on natural resources like gravel.

• Improvement of Agricultural Soil

1. 1. • Steel slag acts as a soil conditioner by neutralizing acidity and providing nutrients (calcium, magnesium, silicon). It is used as a silicate fertilizer to boost crop yields. 

• Production of Cement

1. • Steel slag is a raw material in cement clinker and replaces granulated blast furnace slag in Portland slag cement. This reduces industrial waste and supports sustainable construction

Correct Answer: (d) 1, 2 and 3

Explanation:

• Coal ash contains arsenic, lead, and mercury.

1. 1. • Correct: Coal ash is a by-product of coal combustion and contains toxic heavy metals like arsenic, lead, mercury, cadmium, and chromium. These pose significant health and environmental risks if mismanaged.

• Coal-fired power plants release sulphur dioxide and oxides of nitrogen.

1. 1. • Correct: Burning coal emits sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), which contribute to acid rain, respiratory illnesses, and smog. 

• High ash content is observed in Indian coal.

Correct: Indian coal has 25–45% ash content, significantly higher than imported coal (10–20%). This is due to geological factors (drift theory of coal formation).

Correct Answer: (d) 1, 2 and 3

Explanation:

1. 1. Biochar in Vertical Farming:
      • Biochar is used as part of the growing medium in vertical farming systems. Its porous structure improves soil aeration, water retention, and nutrient availability, enhancing crop productivity.

• Promoting Nitrogen-Fixing Microorganisms:

1. 1. • Biochar creates a conducive habitat for nitrogen-fixing bacteria, increasing soil nitrogen availability. Studies highlight its ability to enhance microbial activity and nitrogen-use efficiency.

• Water Retention:

1. • Biochar’s porous structure allows it to retain water efficiently, reducing irrigation needs.

Biochar is a carbon-rich material produced through pyrolysis (heating biomass at 300–700°C in oxygen-limited conditions). Feedstocks include agricultural residues, wood chips, and manure.

Key Characteristics

• Physical: Porous structure with high surface area, enhancing water and nutrient retention.
• Chemical: Alkaline pH (due to ash content), stable polyaromatic carbon structure.
• Biological: Supports microbial habitats, particularly nitrogen-fixing bacteria.

Agricultural Benefits

• Soil Health Improvement:

1. 1. • Water Retention: Increases soil moisture by 15–20%, reducing irrigation needs (Pacific Biochar, NCBI).
      • Nutrient Efficiency: Reduces fertilizer requirements by 20–30% via nutrient retention (e.g., nitrogen, phosphorus).
      • pH Balancing: Neutralizes acidic soils, enhancing nutrient availability.

• Crop Productivity:

1. 1. • Boosts crop yields by 10–50%, especially in degraded soils (Biochar-US, NCBI).
      • Enhances root growth (30–50% increase in root biomass) and drought resilience.

• Microbial Support:

1. • Increases soil microbial biomass by 20%, fostering nitrogen fixation and organic matter decomposition

Correct Answer: (a) 1, 2, 5 and 6 only

Explanation:

According to India’s National Policy on Biofuels (2018), the following raw materials are approved for biofuel production:

1. Cassava (starch-containing material).
2. Damaged wheat grains (unfit for human consumption).
3. Rotten potatoes (starch-containing material).
4. Sugar beet (sugar-containing material).

Excluded Options:

• Groundnut seeds and Horse gram are not listed under the policy’s approved feedstocks.

Key Policy Provisions:

• Scope Expansion: Allows ethanol production from sugarcane juice, sugar beet, damaged grains, and starch-based materials (e.g., cassava, rotten potatoes).
• Aim: Reduce dependency on fossil fuels, manage agricultural waste, and promote sustainable energy.

Correct Answer: (a) long-term damage done by a tonne of CO₂ emissions in a given year.

Explanation:

The Social Cost of Carbon (SCC) quantifies the monetized economic damages caused by emitting one additional ton of carbon dioxide (CO₂) into the atmosphere. This includes long-term impacts such as:

• Climate-related damages: Reduced agricultural productivity, property loss from sea-level rise, health costs from heatwaves, and ecosystem degradation.
• Global scope: Reflects worldwide harms, not just local or individual effects.
• Policy use: Informs cost-benefit analyses for climate regulations (e.g., carbon taxes, emission standards).

Additional Info:

Key Carbon-Related Goals from Climate Summits and COPs

1. UNFCCC & Kyoto Protocol (1997–2020)

• Kyoto Protocol: Binding emissions cuts for Annex I countries (developed nations) by 5% below 1990 levels (2008–2012).
• Gases Targeted: CO₂, CH₄, N₂O, HFCs, PFCs, SF₆, NF₃.
• Limitations: Excluded major emitters like China/India, Canada withdrew (2012).

2. Paris Agreement (2015)

• Global Temperature Goal: Limit warming to ≤1.5°C (ideally) or ≤2°C above pre-industrial levels.
• Net-Zero Target: Achieve global carbon neutrality by mid-century.
• NDCs: Countries submit 5-year climate action plans (updated by 2025).

3. COP26 (Glasgow, 2021)

• Global Methane Pledge: Reduce methane emissions by 30% by 2030 (vs. 2020).
• Coal Phase-Down: First explicit mention of reducing coal use.
• Deforestation Pledge: Halt deforestation by 2030 (140+ countries).

4. COP27 (Sharm El-Sheikh, 2022)

• Loss and Damage Fund: Established to compensate vulnerable nations for climate impacts.

5. COP28 (Dubai, 2023)

• Fossil Fuel Transition: First agreement to “transition away” from fossil fuels.
• Renewables & Efficiency: Triple renewable energy capacity and double energy efficiency rates by 2030.
• Global Stocktake (GST): Urged countries to enhance NDCs to close the 43% emissions gap for 1.5°C.

6. G20 New Delhi Summit (2023)

• Renewables Goal: Triple global renewable capacity by 2030.
• Net-Zero Pledge: Aim for carbon neutrality by mid-century (no fossil fuel phase-out mentioned).

7. COP29 (Baku, 2024)

• Climate Finance: Channel $300 billion/year to developing nations by 2035.
• Article 6 Finalized: Rules for global carbon markets established.
• Delayed Actions: Postponed decisions on fossil fuels and GST follow-up to COP30 (2025).