Making Cement Greener – Decarbonising India’s Construction Sector

Context

India aims to become a developed country by 2047 and achieve net-zero emissions by 2070. Decarbonising construction is essential because the sector relies heavily on energy-intensive materials such as cement and steel.

1. Construction sector: The broader built environment and its supply chains account for an estimated 35–40% of global greenhouse gas emissions.
2. Cement industry: Cement contributes approximately 7–11% of global CO₂ emissions, making it one of the most difficult sectors to decarbonise.

India’s Cement Industry

1. Global Position: India is the world’s second-largest cement producer, with installed capacity of approximately 668–700 million tonnes per annum (MTPA).
2. Production: Approximately 490 million tonnes in FY 2025–26, recording 8.6% year-on-year growth.
3. Demand Drivers: Housing accounts for around 65% of demand, followed by commercial real estate and public infrastructure projects such as PM Gati Shakti.
4. Per Capita Consumption: Approximately 280–290 kg annually, below the global average.
5. Core Industry: Cement is one of India’s eight core industries and carries a weight of 5.37% in the Index of Industrial Production (IIP).
6. Regional Distribution: South India accounts for approximately 32% of installed capacity.
7. Major Limestone-Rich States: Rajasthan, Andhra Pradesh, Tamil Nadu and Chhattisgarh.
8. Major Companies: UltraTech Cement, Adani Cement (Ambuja Cements and ACC) and Shree Cement.

Cement became a dominant construction material after the development of Portland cement in Britain during the 1820s, owing to its availability, versatility and ability to develop strength relatively quickly.

Understanding Cement’s Environmental Footprint

1. Energy-Intensive Manufacturing: Limestone is mined, mixed with clay and heated in kilns to around 1,450°C. Coal, petroleum coke and natural gas traditionally provide the required heat, resulting in substantial emissions.
2. Process Emissions: During calcination, limestone (calcium carbonate) decomposes into lime (calcium oxide) and carbon dioxide. These emissions occur due to the chemical reaction itself, irrespective of the fuel used. The resulting clinker is ground with gypsum and, depending on the cement type, other materials to produce cement.
3. Wider Environmental Impacts
   1. Land Degradation: Limestone mining removes vegetation and topsoil, disturbs habitats and alters landscapes.
   2. Air Pollution: Cement production releases nitrogen oxides, sulphur dioxide and particulate matter, affecting air quality and human health.
   3. Transportation Emissions: Moving raw materials and finished cement over long distances increases emissions.
   4. Loss of Carbon Sinks: Deforestation and vegetation loss reduce natural carbon sequestration.
   5. Resource Depletion: Intensive extraction puts pressure on mineral resources and local ecosystems.

Therefore, a life-cycle approach is necessary to assess emissions from raw-material extraction, manufacturing, transportation, construction and building use.

India’s Cement Decarbonisation Challenge

1. Current Emissions Intensity: Approximately 0.62 tonnes of CO₂ per tonne of cement.
2. 2030 Target: Reduce emissions intensity to 0.56 tonnes of CO₂ per tonne of cement.
3. 2047 Target: Further reduce it to 0.51 tonnes per tonne of cement.
4. Rising Production: Cement production is projected to reach 1,546 million tonnes by 2070 due to urbanisation and infrastructure expansion.
5. Key Challenge: India must reduce emissions per tonne of cement while meeting rising demand. Improvements in emissions intensity alone may not reduce total emissions if production increases rapidly.

Existing and Proposed Solutions

1. Cleaner Fuels and Energy
   1. Electrification & Renewable Energy: Reduce dependence on fossil fuels in cement manufacturing.
   2. Refuse-Derived Fuel (RDF): Processed combustible waste can partially replace coal and petroleum coke in cement kilns.
   3. Target: NITI Aayog’s roadmap recommends achieving a 20% thermal substitution rate using RDF by 2030, potentially avoiding around 80 million tonnes of cumulative CO₂-equivalent emissions.
   4. Challenges: Requires waste segregation at source, reliable processing facilities and fuel-quality control.
2. Reducing Clinker Content
   1. Current Status: India’s clinker-to-cement ratio is approximately 67.5%, below the global average of 77%.
   2. Problem: Ordinary Portland Cement (OPC) contains more than 95% clinker and is often preferred because of its established performance and faster early-strength development.
   3. Solution: Replace a portion of clinker with supplementary cementitious materials such as fly ash, blast-furnace slag and suitable calcined clay.
   4. Emission Reduction: The International Energy Agency (IEA) estimates that replacing one tonne of clinker can avoid approximately 0.83 tonnes of CO₂ emissions.
   5. Policy Measures: Promote low-carbon cement through government procurement, revised construction specifications, performance-based standards and awareness among developers.
3. Carbon Capture, Utilisation and Storage (CCUS)
   1. Need: Fuel substitution cannot eliminate process emissions from limestone calcination.
   2. Role: CCUS can capture residual CO₂ emissions for utilisation or long-term storage.
   3. Challenges: High investment costs, technological requirements, transport and storage infrastructure, and effective monitoring.
4. Sustainable Building Design
   1. Efficient Architecture: Better planning and structural design can reduce unnecessary cement consumption.
   2. Climate-Responsive Buildings: Designs that minimise heat gain and heat storage reduce cooling requirements and operational energy consumption.
   3. Outcome: Lower material demand & reduced emissions throughout a building’s life cycle.

Traditional Materials and Indigenous Construction

India’s diverse climates and geography have produced construction methods that can reduce dependence on conventional cement-based systems.

1. Compressed Earth Blocks and Rammed Earth: Used in parts of southern India, often with small quantities of cement or lime.
2. Lime-Surkhi Mortar: Uses lime mixed with finely powdered burnt clay or brick material.
3. Natural Binders: Cactus-derived mucilage, lime, mud and suitable industrial by-products such as marble powder can be explored for specific applications.
4. Kath Kuni Architecture: Traditional Himachal Pradesh construction uses alternating timber and dry-stone masonry, often on a raised stone plinth.
5. Elevated Timber and Bamboo Houses: Found in flood-prone and earthquake-prone regions, particularly parts of northeastern India.
6. Limitations: These methods can offer locally appropriate, resource-efficient alternatives but may need adaptation to meet modern construction requirements.

Way Forward

1. Strengthen Circular Economy Practices: Improve waste segregation and reuse suitable industrial by-products, including fly ash and slag, in products such as Portland Pozzolana Cement (PPC) and Portland Slag Cement (PSC).
2. Improve Regulations and Market Incentives: Promote low-carbon building codes, green public infrastructure and transparent disclosure of embodied carbon.
3. Balance Sustainability with Affordability: Ensure low-carbon materials remain affordable and encourage more efficient use of cement.

Conclusion

Decarbonising cement is essential for India to balance infrastructure growth with its net-zero target for 2070. India must combine technological innovation, circular–economy practices and supportive regulations to make construction more sustainable without compromising safety, affordability or development needs.

Frequently Asked Questions (FAQs)

Q1. Why is cement production a major source of carbon emissions?

Cement production releases CO₂ during limestone calcination and through the burning of fossil fuels to heat kilns to around 1,450°C.

Q2. What are the major challenges in decarbonising India’s cement industry?

Key challenges include process emissions, rising cement demand, dependence on fossil fuels, high costs of cleaner technologies and the need to maintain affordability.

Q3. How can reducing the clinker content of cement lower emissions?

Replacing part of the clinker with materials such as fly ash, blast-furnace slag and suitable calcined clay reduces emissions associated with clinker production.

Q4. What is the role of Carbon Capture, Utilisation and Storage (CCUS) in cement decarbonisation?

CCUS can capture residual CO₂ emissions, particularly those from limestone calcination that cannot be eliminated through fuel substitution alone.

Q5. How can traditional construction methods support green buildings in India?

Compressed earth blocks, rammed earth, lime-surkhi mortar, Kath Kuni architecture, timber and bamboo construction can reduce dependence on conventional cement-based materials where locally suitable.