Consider the following statements:

1. Statement I: Studies indicate that carbon dioxide emissions from cement industry account for more than 5% of global carbon emissions.
2. Statement II: Silica-bearing clay is mixed with limestone while manufacturing cement.
3. 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
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

Explanation

Statement I is correct

• Global cement manufacturing is responsible for about 8% of the world’s total CO2 emissions. The cement industry contributes significantly to global CO₂ emissions – both from fuel combustion and from chemical processes such as calcination (heating limestone).

Statement II is correct

• In cement manufacturing, limestone (CaCO₃) is mixed with clay (which contains silica, alumina, etc.) before heating to form clinker.

Statement III is correct and explains statement I

• Limestone is converted into lime during clinker production for cement manufacturing. This refers to the calcination process: CaCO₃ (limestone)→CaO (lime)+CO₂. This process releases a significant amount of CO₂, which directly explains Statement I.
• Clinker is the primary component in cement and is extremely carbon-intensive, making up 90% of overall emissions from cement.

Answer: (b) Both Statement II and Statement III are correct but only one of them explains Statement I; Difficulty Level: Medium