🧷 Authentic Classroom Explanation by IAS Monk

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📌 The Question:

Environment & Ecology

Consider the following statements:

Statement I:
Studies indicate that carbon dioxide emissions from cement industry account for more than 5% of global carbon emissions.

Statement II:
Silica-bearing clay is mixed with limestone while manufacturing cement.

Statement III:
Limestone is converted into lime during clinker production for cement manufacturing.

Which one of the following is correct in respect of the above statements?

(a) Both Statement II and Statement III are correct and both of them explain Statement I
(b) Both Statement II and Statement III are correct but only one of them explains Statement I
(c) Only one of the Statements II and III is correct and that explains Statement I
(d) Neither Statement II nor Statement III is correct

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✅ Correct Answer: (a)

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🔍 Curiosity Raiser

Why does a material as common as cement quietly rival entire nations in carbon emissions?

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🌱 Enrich Notes (UPSC Value Add)

• Cement industry contributes ~7–8% of global anthropogenic CO₂ emissions
• Consumes 2–3% of global energy supply
• Emissions arise from:
  • Chemical process (calcination)
  • Energy-intensive high-temperature kilns

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🧠 Authentic Classroom Explanation

Statement II — ✔️ Correct

• Cement manufacturing involves mixing:
  • Limestone (CaCO₃)
  • Silica-bearing clay
• This process requires very high temperatures (~1450°C), leading to massive energy use and CO₂ emissions from fuel combustion.

Statement III — ✔️ Correct

• During clinker production (calcination):
  • Limestone (CaCO₃) → Lime (CaO) + CO₂
• This chemical decomposition alone contributes ~50% of cement-sector emissions.

Link to Statement I:

• CO₂ emissions come from:
  1. Chemical release during calcination (Statement III)
  2. Energy use in heating limestone–clay mixture (Statement II)

✅ Thus, both Statement II and Statement III are correct and both explain Statement I.

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🕯️ IAS Monk Whisper

Some emissions come not from excess,
but from the very chemistry of progress.