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 with respect to the above statements?   

  • Both Statement II and Statement III are correct and both of them explain Statement I   
  • Both Statement II and Statement III are correct but only one of them explains Statement I   
  • Only one of the Statements II and Statement  III is correct and that explain statement t I   
  • Neither Statement II nor Statement III is correct 

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

  • The cement industry is a significant source of carbon dioxide emissions due to both the chemical reactions involved in producing clinker (the main ingredient of cement) and the burning of fossil fuels to power the production process. Specifically, calcining limestone (a primary ingredient) to produce lime (CaO) releases CO2, and burning fossil fuels to heat the kilns also contributes to emissions.
  • The cement industry is a major global polluter, currently accounting for approximately 6.5% to 8% of total global CO2 emissions. If the sector were a country, it would be the third or fourth largest emitter in the world.
    • Global cement manufacturing produced 1.6 billion metric tonnes of CO2 in 2022, the latest year for which there are figures – that’s about 8% of the world’s total CO2 emissions.
  • Silica-bearing clay is mixed with limestone while manufacturing cement. Cement production involves mixing limestone with other materials like clay, which contains silica, along with other minerals. These materials are then processed into clinker, a key component of cement.
  • In the process of making cement clinker, limestone, which is primarily calcium carbonate (CaCO3), is heated to high temperatures (1450°C or 2640°F) in a kiln. This process, called calcination, decomposes the limestone into calcium oxide (CaO), commonly known as lime, and carbon dioxide (CO2). The lime then reacts with other raw materials like clay and silica to form the clinker, which is the main ingredient in cement.