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UPSC Prelims 2025 GS Paper 1, question 31

Topic: Environment and ecology

Q31

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?

  1. (a) Both Statement-II and Statement-III are correct and both of them explain Statement-I
  2. (b) Both Statement-II and Statement-III are correct but only one of them explains Statement-ICorrect answer
  3. (c) Only one of the Statements II and III is correct and that explains Statement-I
  4. (d) Neither Statement-II nor Statement-III is correct

Solution.

Answer: (b) Both Statement-II and Statement-III are correct but only one of them explains Statement-I

  1. Statement-I is correct: the global cement industry accounts for about 7-8% (more than 5%) of global anthropogenic carbon dioxide emissions.
  2. Statement-II is correct, but it does not explain Statement-I: mixing silica-bearing clay with limestone describes the raw material composition for cement manufacturing rather than the process that releases carbon dioxide.
  3. Statement-III is correct and explains Statement-I: during clinker production, thermal calcination converts limestone into lime (CaCO3→CaO+CO2\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2), directly releasing large volumes of carbon dioxide.