"Why Cement Remains a Hard Barrier to India's Net-Zero Goal"
Calcination
chemical reaction in which heated limestone breaks down, releasing carbon dioxide and forming lime
Clinker
small, stone-like lumps formed when limestone and clay are heated together in a kiln
India wants to become an economically developed country by 2047 and reach net-zero emissions by 2070. The construction sector is very important for both goals. Construction uses steel and cement. Globally, construction-related activity causes 35% to 40% of all greenhouse gas emissions. Cement making needs very high kiln temperatures. Calcination releases carbon dioxide when limestone is heated. Because of this chemical reaction, cement is a hard-to-abate sector. Cleaner energy alone cannot fix its emissions. The cement sector contributes 7% to 11% of global greenhouse gas emissions. This is almost double the share of the aviation industry. India's broader industrial sector includes cement. It already produces over a fifth of national emissions. Existing tools like the Perform, Achieve and Trade scheme and the Carbon Credit Trading Scheme push large industrial units toward lower energy use. But cement's chemical emissions sit outside what energy efficiency alone can solve.
Cement is a fairly recent material in human history. Builders used mineral-based binders long before cement existed. Portland cement is the standard binder used today. It was developed in Britain in the 1820s to meet the demands of fast industrialisation. Before that, builders used lime mortars, lime-surkhi mortars, mud and clay mortars, gypsum-based materials, and naturally pozzolanic materials. A pozzolanic material reacts with calcium hydroxide in water. It forms cement-like compounds without being cement itself. The Taj Mahal was built using lime mortar. Roman buildings used lime with volcanic pozzolanic material. Both still stand centuries later. This shows alternatives are technically possible. But cement has become deeply built into the construction industry. Standard specifications, supply chains and marketing all use cement. Moving away from it is now mostly an economic and institutional challenge, not a technological one.
Silica-bearing clay is mixed with limestone during cement manufacturing. This forms the raw mix. Limestone is converted into lime (calcium oxide) during the calcination process. This happens in clinker production. CO₂ is released as a byproduct of this chemical reaction.
Limestone is the raw material for cement. It forms when calcium-rich marine life such as corals and oysters fossilise. They get compressed over millions of years. Mining limestone means clearing forests and topsoil. This exposes the rock layer below. The depth varies by region. Once limestone reaches a factory, workers mix it with clay. They heat the mixture to about 1,450°C. Heating kilns to 1,450°C causes 35% to 40% of cement-making emissions. This step usually runs on coal or petroleum coke. Mixing silica-bearing clay with limestone is part of preparing the raw material. It does not by itself release carbon dioxide.
The actual carbon release happens through calcination. This is a chemical reaction. Heated limestone breaks down and gives off carbon dioxide. …
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?
With reference to greenhouse gas emissions from the cement sector, consider the following statements:
1.The cement industry's share of global greenhouse gas emissions is roughly double that of the aviation sector.
2.Emissions from limestone calcination are classified as energy-related emissions rather than process emissions.
3.Indirect effects such as deforestation for limestone mining and long-distance transport are typically excluded from standard emission accounting for cement.
Which of the statements given above is/are correct?
Consider the following statements regarding emissions from cement manufacturing:
1.Calcination of limestone, via clinker formation, is the single largest source of emissions in cement production.
2.Heating cement kilns to about 1,450°C accounts for the entire carbon footprint of cement-making.
3.Clinker is composed of calcium silicates, calcium aluminates and calcium aluminoferrites.
How many of the above statements are correct?
Match List-I (binder/material) with List-II (defining fact) and select the correct answer using the codes given below:
List-I
A.Portland cement
B.Pozzolanic material
C.Lime mortar
List-II
1.Reacts with calcium hydroxide in water to form cementitious compounds without itself being cement
2.Developed in Britain in the 1820s
3.Used in historic structures such as the Taj Mahal
Consider the following statements regarding limestone, the key raw material for cement:
1.It forms from fossilised, calcium-rich marine organisms compressed over millions of years.
2.In India, it is found only within 10 metres of the surface.
3.It occurs in states such as Karnataka, Chhattisgarh, Andhra Pradesh and Rajasthan.
Which of the statements given above is/are correct?
Which of the following statements about India's climate commitments is/are correct?
1.India aims to become an economically developed country by 2047.
2.India aims to achieve net-zero emissions by 2070.
Select the correct answer using the code given below:
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