India's Cement Sector Poses Major Hurdle to 2070 Net-Zero Climate Goals

India aims to become a developed economy by 2047 and a net-zero emissions economy by 2070, but the construction sector poses a major hurdle. The global construction footprint contributes 35% to 40% of all greenhouse gas emissions, driven largely by the extreme heat needed for steel and cement.

The Cement Problem

Cement production is uniquely difficult to decarbonize because of limestone calcination, a chemical reaction accounting for 7% to 11% of emissions. Traditional Portland cement consists of over 95% clinker mixed with gypsum. Making clinker involves heating limestone with clay to around 1,450 degrees Celsius, which generates small stone-like balls and releases carbon dioxide. The heating process itself accounts for 35% to 40% of cement-making emissions, while the chemical breakdown of limestone accounts for 53% to 65%.

Environmental Impact

Beyond manufacturing, limestone mining destroys forests and fertile topsoil. Depending on the region, miners dig 30 to 60 meters under the topsoil in states like Karnataka, Chhattisgarh, and Andhra Pradesh, and at shallower depths in Rajasthan. Hidden carbon costs also include cutting down hills, long-distance transport, and the loss of vegetation and carbon sequestration. Manufacturing also releases air pollutants such as nitrogen oxides, sulphur dioxide, and particulate matter.

Potential Solutions

India's cement industry currently emits 0.62 tonnes of carbon dioxide per tonne of cement. Experts from The Energy and Resources Institute recommend reducing this to 0.56 tonnes by 2030 and 0.51 tonnes by 2047, while cement production is projected to rise from 334 million tonnes in 2019-20 to 1,546 million tonnes in 2070. Alternatives include using lime-based, mud, or gypsum binders, as seen historically in the Taj Mahal and Roman buildings. Dr. Nandini Halder from Vishwakarma University notes that the real challenge is the enormous commercial ecosystem built around cement rather than missing technology. NITI Aayog's decarbonisation roadmap also suggests replacing coal with refuse-derived fuel from municipal solid waste to achieve a 20% thermal substitution rate by 2030. Furthermore, replacing clinker with industrial by-products like slag can avoid 0.83 tonnes of carbon dioxide emissions per tonne replaced, though average substitution cannot exceed 40% without risking building integrity.

Context

India's vast infrastructure expansion requires massive amounts of building materials, making heavy industries central to any national climate strategy. Balancing rapid industrial growth with strict carbon reduction targets remains one of the defining policy challenges for the country in the coming decades.