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?
Explanation:
Statement I: The cement industry is a major contributor to global CO2 emissions, typically accounting for 5-8% of global anthropogenic CO2. So, 'more than 5%' is correct. Statement II: Cement production involves heating limestone (calcium carbonate) with other materials like clay (silica, alumina, iron oxides) in a kiln. This statement is factually correct regarding the raw materials. Statement III: During clinker production, limestone (CaCO3) undergoes calcination at high temperatures, converting it into lime (CaO) and releasing carbon dioxide (CO2). This chemical reaction (CaCO3 → CaO + CO2) is a primary source of process-related CO2 emissions in cement manufacturing. This statement is correct. Explanation: Both Statement II and Statement III are correct. Statement III directly explains *why* the cement industry has high CO2 emissions (as stated in Statement I) because the calcination of limestone releases CO2. Statement II describes the raw materials but does not directly explain the *emissions* themselves. Therefore, only Statement III explains Statement I.