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?
Show answer
Answer: B. Statement I is correct: cement production causes about 7-8% of global CO2 emissions. Statement II is correct: silica-bearing clay is mixed with limestone as raw material, but this fact does not explain the emissions. Statement III is correct and explains Statement I: in the kiln, limestone (CaCO3) is heated and turns into lime (CaO), releasing CO2 (calcination), which is the main source of cement's emissions. So both are correct but only III explains I.
Watch for: A correct fact about raw materials (Statement II) is not the same as the cause of emissions (calcination in Statement III).
Why the other options are wrong
- A. Wrong: mixing clay with limestone does not by itself release the CO2; only Statement III explains Statement I.
- C. Wrong: both Statement II and Statement III are correct.
- D. Wrong: both Statement II and Statement III are correct.
Source to check: IEA, Cement tracking report; Chatham House report 'Making Concrete Change' (2018); NCERT Class X Geography, 'Manufacturing Industries' (cement).
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.