Accelerating sustainability in the cement industry through alternative fuels and raw materials is key to reducing carbon emissions, optimising resources, and advancing circular economy initiatives. As the industry moves towards a low-carbon future, ICR discusses these critical developments with industry experts.
The cement industry plays a crucial role in infrastructure development and economic growth. However, it is also one of the most carbon-intensive industries, responsible for nearly seven per cent of global CO2 emissions (IEA, 2023). The industry’s heavy reliance on fossil fuels such as coal and petroleum coke, combined with the high emissions from clinker production, has led to growing concerns over its environmental impact.
To address these challenges, cement manufacturers worldwide are increasingly adopting alternative fuels and raw materials (AFR) as part of their sustainability strategies. AFR not only helps in reducing carbon emissions but also supports waste management by utilising industrial by-products and municipal waste. By replacing conventional fuels and raw materials with more sustainable alternatives, the cement industry can significantly lower its environmental footprint while contributing to the circular economy.
Traditional cement manufacturing processes consume large amounts of natural resources, including limestone, clay, and fossil fuels. The production
of one tonne of cement generates approximately 0.9 tonnes of CO2, with the calcination of limestone contributing to 60 per cent of total emissions, while the burning of fossil fuels accounts for the remaining 40 per cent (GCCA, 2023). With global demand for cement expected to rise due to rapid urbanisation and infrastructure expansion, the urgency to adopt low-carbon alternatives has never been greater.
A study by the Global Cement and Concrete Association (GCCA, 2023) highlights that to achieve net-zero emissions by 2050, the cement industry must reduce its carbon footprint by at least 40 per cent by 2030. Alternative fuels and raw materials present a viable pathway to achieving this goal by replacing traditional carbon-intensive inputs with more sustainable and energy-efficient options.
Reducing fossil fuel dependency in cement kilns
Cement kilns operate at extremely high temperatures—often exceeding 1,400°C—making them highly suitable for the incineration of alternative fuels. These high temperatures ensure complete combustion, effectively neutralising pollutants and reducing waste disposal challenges. The most commonly used alternative fuels in cement manufacturing include:
Municipal Solid Waste (MSW) and Refuse-Derived Fuel (RDF)
Municipal solid waste, particularly its non-recyclable components, can be processed into refuse-derived fuel (RDF), which serves as a viable replacement for coal. RDF is composed of materials such as plastics, paper, textiles, and organic waste, which are processed to achieve a high calorific value.
In India, the use of RDF has increased by 12 per cent annually, driven by government initiatives like the Swachh Bharat Mission and the Central Pollution Control Board (CPCB) directives on waste-to-energy projects. Cement plants that integrate RDF in their fuel mix not only reduce reliance on fossil fuels but also contribute to municipal
waste management, preventing large-scale landfill accumulation.
Biomass and agricultural waste
India generates over 500 million tonnes of agricultural waste annually (NITI Aayog, 2022), a significant portion of which goes unutilised or is burned in open fields, contributing to severe air pollution. By leveraging biomass materials such as rice husks, sawdust, coconut shells, sugarcane bagasse, and groundnut shells, cement kilns can replace conventional fuels with carbon-neutral alternatives.
Biomass combustion releases only the CO2 absorbed by plants during their growth cycle, making it an environmentally friendly energy source. Moreover, cement plants using biomass benefit from reduced fuel costs and government incentives for sustainable energy adoption.
Tushar Khandhadia, General Manager – Production, Udaipur Cement Works, says, “Alternative fuels (such as biomass, waste-derived fuels or industrial by-products) often have lower energy content compared to traditional fuels like coal or pet coke. This means that more of the alternative fuel is required to achieve the same level of heat generation. As a result, more fuel needs to be burned, potentially increasing the overall heat consumption of the kiln.”
“Some alternative fuels have higher moisture content or volatile substances, requiring additional energy to evaporate the moisture or combust these volatile compounds. This can lead to a higher heat consumption during the combustion process,”he adds.
Scrap tires and rubber waste
Discarded rubber tires pose a significant waste disposal challenge, with millions accumulating in landfills each year. Cement kilns provide an ideal solution by using shredded tires as an alternative fuel, leveraging their high calorific value, which is comparable to coal. Studies indicate that each ton of scrap tires used in cement kilns can replace approximately 0.7 tonnes of coal, resulting in substantial CO2 emission reductions (CEMBUREAU, 2023).
Industrial and hazardous waste
Cement kilns are also used to incinerate industrial and hazardous waste, including solvents, paint sludge, petrochemical residues and pharmaceutical waste. The extreme temperatures and long residence times in kilns ensure complete combustion, preventing toxic emissions.
India’s Hazardous Waste Management Rules (2016) encourage industries to co-process their waste in cement plants rather than disposing of it in landfills, thus minimising environmental risks while supporting sustainable fuel alternatives.
S Sathish, Partner and National Sector Leader – Industrial Manufacturing, KPMG India, says, “Energy and fuel cost is one of the key costs for cement sector. While a lot of focus has been done on energy consumption optimisation, waste heat recovery areas, buying optimisation of coal and petcoke is a new area, which cement companies are focusing on. Having an AI-based model to optimise the buying cost of fuel, based on petcoke price trends, price trends of coal from different sources, both import and domestic, quality variation analysis of different sources, etc. is a best practice adopted by some leading players to optimise fuel buying. Exploration with green fuels and alternative fuel resources is another big area cement players are working on.”
AFR: A sustainable approach to clinker reduction
The production of clinker, the key ingredient in cement, is highly energy-intensive and generates a significant amount of CO2. By using alternative raw materials (ARMs), manufacturers can reduce their clinker factor, leading to lower emissions and improved resource efficiency.
While replacing fossil fuels like coal and pet coke with alternative fuels can help lower CO2 emissions in the cement industry, the overall reduction is often limited—typically ranging from 1–5 per cent in most cases, with a maximum potential of 18 per cent in select scenarios. The extent of reduction depends largely on the biogenic content of the alternative fuel source. Additionally, certain alternative fuels contain higher levels of sulphur, nitrogen, chlorine, heavy metals and other volatile compounds, which can lead to increased emissions of non-CO2 air pollutants. As a result, maintaining control over emissions—beyond just CO2, including SOX and NOX—has become a key focus. To mitigate these risks, ongoing investments have been necessary as the use of refuse-derived fuel (RDF) continues
to grow.
The most widely used ARMs in cement production include:
Fly ash and bottom ash
Fly ash, a by-product of coal-fired thermal power plants, has gained widespread adoption as a partial clinker substitute. India produces around 226 million tonnes of fly ash annually (CEA, 2023), a substantial portion of which can be utilised in cement production.
Fly ash not only reduces CO2 emissions but also enhances cement properties such as durability, workability, and resistance to sulfate attacks. The Bureau of Indian Standards (BIS) allows up to 35 per cent fly ash in Portland
Pozzolana Cement
(PPC), making it a key component of sustainable cement formulations.
Steel slag and granulated blast furnace slag (GBFS)
The steel industry generates approximately 25 million tonnes of slag annually (Ministry of Steel, 2023). Granulated Blast Furnace Slag (GBFS) is a valuable clinker substitute, with the potential to replace up to 60 per cent of clinker in cement production.
GBFS-based cement exhibits superior strength, durability, and resistance to harsh environmental conditions, making it a preferred choice for infrastructure projects, marine structures, and
road construction.
Olli Hänninen, Owner and Co-founder, Moviator Oy says “The key advantage of using slag today is its ability to reduce CO2 emissions. Cement production relies on four key oxides: calcium oxide, silicon oxide, aluminum oxide and iron oxide—all of which are present in slag. Since slag has already undergone thermal treatment, its use in cement manufacturing requires less energy. As a result, producing cement with slag generates lower CO2 emissions.”
Limestone calcined clay cement (LC3)
Limestone calcined clay cement (LC3) is an innovative low-carbon cement that reduces clinker content by 50 per cent, significantly lowering energy consumption and CO2 emissions. Research conducted by IIT Delhi and EPFL Switzerland suggests that LC3 cement has 25 per cent to 30 per cent lower CO2 emissions compared to Ordinary Portland Cement (OPC) while maintaining comparable strength and performance.
Challenges in large-scale AFR adoption
Despite the significant benefits of AFR, its widespread adoption in India remains limited, accounting for less than 5 per cent of total cement production, compared to 40 per cent in Germany and 60 per cent in the Netherlands (GCCA, 2023). Key challenges include:
Lack of infrastructure for waste collection, sorting, and processing.
Variability in AFR quality, leading to inconsistent combustion efficiency.
Regulatory hurdles in obtaining permits for hazardous waste co-processing.
Limited public awareness about the environmental benefits of AFR.
Strategies for enhancing AFR utilisation
To accelerate the adoption of AFR in India, cement manufacturers must focus on:
1. Developing pre-processing facilities: Establishing regional AFR hubs for waste segregation and processing.
2. Enhancing policy incentives: Government support through tax benefits, subsidies and carbon credits.
3. Industry collaboration: Partnerships between cement companies, municipalities and waste management firms.
4. Advanced emission monitoring: Implementing real-time air quality sensors to ensure compliance with environmental norms.
Andrey Korablin, Founder, SmartScrap, says, “One of the biggest challenges is the human factor. Unfortunately, in many industrial enterprises, people are resistant to change. This is not only because mid-level employees are reluctant to adapt but also due to a lack of proper motivation for using alternative raw materials. In many cases, alternative materials can initially lead to lower productivity or increased energy consumption.”
“These factors directly impact key performance indicators (KPIs) for employees. If using alternative raw materials negatively affects these KPIs, it can also reduce their salaries. Additionally, there is little incentive for employees to seek alternative solutions—if their initiative proves successful, they may receive no financial reward. However, if they make a mistake, they could be demotivated or even risk losing their jobs. This is why, at the top management level, it is crucial to create a system of motivation and a company culture that encourages change and innovation,”
he adds.
Conclusion
The integration of alternative fuels and raw materials is essential for the cement industry’s transition towards low-carbon and sustainable manufacturing practices. By replacing fossil fuels and traditional raw materials with eco-friendly alternatives, the industry can significantly reduce emissions, lower energy consumption, and contribute to a circular economy. With the right policies, technological advancements, and industry collaboration, AFR adoption in India can scale up, paving the way for a more sustainable and resilient cement sector.
– Kanika Mathur
