Question 61
Set 3
Contents
QQuestion
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?
OOptions
✓Correct Answer
DDalvoy Solutions
Statement I: The cement industry does account for more than 5% of global carbon emissions (approximately 8% according to recent studies), making it a significant contributor to greenhouse gas emissions.
Statement II: Correct and explains Statement I. Silica-bearing clay (along with iron ore and alumina sources) is indeed mixed with limestone in cement manufacturing. The limestone provides calcium oxide, which is the primary component of cement.
Statement III: Correct and explains Statement I. During clinker production, limestone (CaCO₃) is heated to high temperatures (around 1450°C) and decomposes to form lime (CaO) and carbon dioxide. This process, called calcination, releases large amounts of CO₂, which is why cement production is so carbon-intensive.
Both statements explain the high carbon emissions from cement manufacturing.
SUPSC Prelims Strategy and Tips
For industrial process questions, understand both the raw materials used and the chemical reactions involved. The cement industry's high emissions come from both energy use and chemical processes.