Concrete

Clinker factor determines the CO2 footprint of cement

Published

4 years ago

June 13, 2022

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Manoj Kumar Rustagi, Chief Sustainability and Innovation Office (CSIO), JSW Cement, gives insights into the process of producing blended cement with supplementary cementitious materials for more strength and durability.

What are the core raw materials used in the production of cement?
Cement manufacturing is an energy and resource intensive process. Primary raw material is limestone which is mined, crushed, ground and mixed with bauxite, iron ore and other additives/correctives to make raw meal which is then heated to a temperature as high as ~1400°C in a horizontal kiln. Coal is the primary fuel which provides energy for the combustion process. The hot material is then cooled down to form clinker, an intermediate product for making cement. Clinker is further ground and blended with gypsum (mineral or chemical) to make the final product called ordinary Portland cement (OPC).
When clinker is blended with other supplementary cementitious materials like fly ash or slag or both, the product is known as blended cement.

What are the alternative raw materials that can be used in the production of cement? How does that impact the process of production?
Cement sector accounts for ~7 per cent of global CO2 emissions, and therefore it needs to be aggressive on its decarbonisation strategy wherein one of the primary lever is using alternative raw materials for the production of clinker and supplementary cementitious materials (SCMs) as cement/clinker replacements. Different fine-grained silica, silicate and alumina-silicate materials either natural or synthetic can be used in the final cement product to obtain a new eco-friendly cementitious binder with similar or better properties. The most commonly used SCMs are fly ash, granulated blast furnace slag, natural volcanic pozzolana etc.
When clinker is blended with other supplementary cementitious materials like fly ash, slag or both, products are called Portland Pozzolona Cement (PPC), Portland Slag Cement (PSC) and composite cement (CC) respectively. Blended cement products have a much lower carbon footprint than OPC. Since clinker manufacturing is the phase where most thermal energy is consumed and CO2 is emitted, reducing clinker factor in cement not only results in lowering the process CO2 but also the thermal energy and electrical energy requirements.
There are other alternative raw materials like Spent Pot Liner (SPL), red mud, lime sludge and steel slag, which are used in the clinker manufacturing to reduce consumption of limestone and consequently reducing the process CO2 that comes from limestone calcination.

Can cement maintain its quality standard with inclusion of supplementary raw materials as against limestone?
Yes, blended cement products not only maintain the most quality standards as OPC but also have superior properties in various parameters when compared to conventional OPC. Blended cements are preferred for its late strength, chemical resistance, alkali resistance and for coastal applications and dams and irrigation projects where they are technically most suitable.
The use of SCMs/mineral admixture/blended cements in concrete significantly helps in mitigating the expansion due to alkali silica reaction (ASR), due to the reduction in the availability of alkalis in the pore solution and the refinement of the pore structure. Not only does this reduce maintenance costs of infrastructure such as dams and bridges, but also allows the consumption of local aggregates that may contain deleterious materials. The reduced expansion in SCM-blended structures reduces the risk of expansion and cracking. This pozzolanic reaction also has a beneficial impact on resistance to sulphate attack.
Recently GCCA, India has published a detailed report on Benefits of Blended Cement Products, which has been prepared by NCCBM and reviewed by IIT, Madras, and that captures all the environment and technical benefits.

Explain the impact on carbon emission of the production unit when alternative raw materials are used in various proportions.
In cement manufacturing, CO2 is primarily emitted as a result of the chemical conversion process used in the production of clinker in which limestone (CaCO3) is first converted to lime (CaO) and then to hydraulic compounds. CO2 is also emitted during cement production by fossil fuel (primarily coal) combustion. Thus ~80-85 per cent of the CO2 emissions could be attributed to the production of clinker. This is partly reduced by using alternative raw materials and mineralisers in the raw mix design of clinker.
The amount of clinker in cement, known as clinker factor, determines the CO2 footprint of cement. In OPC, clinker factor is ~90 per cent thus, it has a carbon footprint of around 800 – 850 kg/MT of cement. When clinker is replaced with SCMs, the CO2 emissions are reduced as SCMs don’t have embodied carbon emissions. That is why blended cement have much lower carbon footprint than OPC. Currently in Portland Slag Cement (PSC) production almost 60 to 65 per cent of clinker is replaced with slag which results in ~60 per cent of CO2 footprint and the final carbon footprint is around 300 – 350 kg/MT. Similarly, in PPC where ~35 per cent of clinker is replaced, carbon footprint will be in the range of 500 – 550 kg/MT.

-Kanika Mathur

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Technology plays a vital role in utilising alternative materials

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Concrete

Cement Makers Reaffirm Commitment to Sustainable Growth

Published

6 days ago

June 5, 2026

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World Environment Day spotlight on innovation and circularity

On World Environment Day, the Indian cement industry reiterated its commitment to supporting India’s climate ambitions through sustainable manufacturing, resource efficiency and the adoption of cleaner technologies.

The Cement Manufacturers’ Association (CMA) said the sector remains aligned with the Government of India’s Net Zero commitments and is accelerating efforts to reduce its environmental footprint while supporting the country’s infrastructure and development agenda.

Parth Jindal, President, CMA and Managing Director, JSW Cement, said the industry is increasingly adopting cleaner technologies, improving energy efficiency and expanding the use of alternative fuels and raw materials. He also highlighted the growing importance of circular economy practices, where industrial by-products and waste streams from one sector are utilised as resources in another.

“The Indian Cement Industry is aligned to the Government’s commitments on carbon mitigation and is accelerating the adoption of cleaner technologies, resource efficiency and circular economy practices while actively exploring the potential of Carbon Capture, Utilisation and Storage (CCUS) as a critical pathway for deep decarbonisation,” said Jindal.

He added that coprocessing industrial waste and by-products helps conserve natural resources, reduce disposal requirements and lower the environmental footprint across multiple sectors.

According to Jindal, sustainability is no longer limited to manufacturing processes but is increasingly influencing investment decisions, innovation strategies and long-term growth plans within the industry.

Echoing similar views, Dr Raghavpat Singhania, Vice President, CMA and Managing Director, JK Cement, said sustainable development extends beyond emissions reduction and must also focus on responsible resource utilisation and waste minimisation.

“Sustainability in the built environment cannot be measured by emissions alone. It is equally about how efficiently we use resources, how effectively we minimise waste and how responsibly we create the infrastructure that will serve future generations,” said Singhania.

He noted that the cement industry is advancing its sustainability agenda through greater resource efficiency, increased circularity, technological innovation and continuous improvements in manufacturing practices. As a key contributor to India’s infrastructure development, the sector has a critical role to play in balancing economic growth with environmental responsibility.

On the occasion of World Environment Day, industry leaders reaffirmed their commitment to supporting India’s climate goals while delivering the materials required for resilient, durable and sustainable infrastructure.

Concrete

Building a Greener Future Together

Published

7 days ago

June 4, 2026

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Environmental sustainability requires immediate action, not just long-term commitments and discussions. Recycling, circular economy practices, and technology-driven waste management can help industries reduce environmental impact while supporting sustainable growth.

Author: Jignesh Kundaria, Director and CEO, Fornnax Technology

World Environment Day serves as an important reminder that environmental sustainability can no longer remain confined to discussions, reports, or long-term commitments. The environmental challenges facing the world today demand immediate, measurable, and collective action. Across industries and communities, waste generation continues to outpace our ability to process it responsibly, placing increasing pressure on ecosystems, natural resources, public health, and the well-being of future generations.

One of the most significant shifts required today is a change in how society perceives waste. Rather than being viewed as a material to be discarded, waste must be recognised as a valuable resource that can contribute to both economic growth and environmental protection when managed through the right technologies and systems. This mindset forms the foundation of the circular economy model that countries across the world are increasingly adopting to reduce landfill dependence, recover valuable materials, and create more sustainable industrial ecosystems.

India has made meaningful progress in strengthening awareness around sustainability, recycling, and environmental responsibility over the past decade. Significant efforts are being made to formalise the recycling sector through improved infrastructure, technology adoption, policy implementation, and broader stakeholder participation. These developments are creating a stronger foundation for responsible waste management and resource recovery across the country.

However, achieving long-term environmental impact requires collaboration from all stakeholders. Industries, policymakers, technology providers, and communities must work together with greater accountability to strengthen recycling ecosystems, encourage responsible waste management practices, and create sustainable outcomes through consistent execution rather than temporary interventions.

As someone closely associated with the recycling industry, I firmly believe that technology will play a decisive role in addressing future environmental challenges. Advanced recycling systems have the potential to recover valuable resources, reduce pollution, minimise landfill burdens, and conserve energy, creating a more sustainable future for generations to come. This belief is deeply reflected in Fornnax’s motto, “Committed to Create a Green Future,” which embodies our commitment to building long-term environmental value through innovation and responsible action.

At the same time, technology alone cannot deliver meaningful change. Real progress requires intent, awareness, participation, and a shared sense of responsibility. Sustainable development can only be achieved when innovation is supported by collective action and a genuine commitment to environmental stewardship.

On this World Environment Day, let us move beyond conversations and take meaningful steps towards creating a cleaner, greener, and more sustainable planet. By embracing innovation, strengthening recycling ecosystems, and acting responsibly today, we can create lasting environmental impact and secure a better future for generations to come.

Concrete

JK Lakshmi Advances LC3 Cement Expansion

Company highlights commercial production and research partnerships

Published

1 week ago

June 1, 2026

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The meeting reviewed progress in limestone calcined clay cement (LC3) technology and its commercial adoption in India’s cement sector, focusing on low-carbon alternatives to conventional binders. JK Lakshmi Cement noted that limestone calcined clay cement can reduce carbon dioxide emissions by up to 40 per cent compared with conventional cement and said this reduction supports industry decarbonisation. The company highlighted that it was among the first two cement manufacturers in India to move LC3 into commercial production after the Bureau of Indian Standards approved the technology as a cement standard.

Vinita Singhania said the transition of LC3 from research to commercial production reflected collaboration between industry, academia and international institutions. Maya Tissafi acknowledged JK Lakshmi Cement’s role in advancing LC3 adoption in India and its contribution in taking the technology from laboratory trials to commercial implementation. Both representatives underlined the growing relevance of sustainable construction materials as India expands infrastructure and urban development.

The meeting explored continued collaboration with Swiss research institutions such as EPFL, EMPA and ETH Zurich alongside Indian academic partners and development organisations. JK Lakshmi Cement has been associated with the LC3 initiative since 2014 and worked with EPFL, IIT Delhi, IIT Madras, Development Alternatives and Technology and Action for Rural Advancement. The company conducted one of the earliest industrial trials of LC3 and recently announced commercial production of Green Pro LC3 cement from its Jaykaypuram plant in Rajasthan.

India remains the world’s second-largest cement producer and expansion of infrastructure, urbanisation and housing demand continue to support long-term sector growth, increasing interest in low-carbon technologies. The company reported an annual turnover of more than Rupees (Rs) 60 bn and current cement capacity of about 18 million (mn) tonnes (t) per annum, with a target of reaching 30 million (mn) tonnes (t) by 2030. Apart from grey cement, the company also makes ready-mix concrete, gypsum plaster, wall putty, primers, adhesives and fly ash blocks, and both sides concluded on the need for continued collaboration to develop sustainable construction solutions.