UPSC Previous Year Question | Prelims GS | 2025

Consider the following statements: Statement I: Studies indicate that carbon dioxide emissions from the 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?

  1. Both Statement II and Statement III are correct and both of them explain Statement I
  2. Both Statement II and Statement III are correct but only one of them explains Statement I
  3. Only one of the Statements II and III is correct and that explains Statement I
  4. Neither Statement II nor Statement III is correct

Answer

Correct Answer

Both Statement II and Statement III are correct but only one of them explains Statement I

Explanation

Silica-bearing clay is indeed mixed with limestone in cement manufacturing (Statement II, true), and limestone (calcium carbonate) is converted to lime (calcium oxide) during clinker production, releasing CO2 (Statement III, true). However, only the calcination step (Statement III) directly explains the large CO2 emissions referred to in Statement I; the clay-mixing step (II) does not directly explain the emissions.

Topics: carbon emissions, cement industry, environment