Use of alternative fuels in cement kilns can create a win-win situation for cement companies and urban local bodies by promoting better waste management practices.
Though there are many ways through which cost advantage of a cement company could be improved, increasing the use of alternative fuels and raw materials (AFR) is one of the important means to achieve the goal. Since the fuel costs have shown an upward trend over last few years, affecting the total manufacturing cost at their plants, the focus on AFR substitution rates have increased in the cement manufacturing process.
The use of AFR reduces carbon emissions that result from using fossil fuels and reduce the overall environmental impact of cement manufacturing process and will help in achieving industry and national emission targets.
The Indian cement industry has set voluntary and ambitious emission reduction targets to reduce 45 per cent of its carbon emissions intensity by 2050 from the 2010 levels. As one of the global leaders in energy efficiency, the Indian cement industry has also committed to reduce 377 - 485 PJ of energy in 2050 compared to business-as-usual (BAU) scenario. Moreover, the Government has committed to reduce emissions intensity of its Gross Domestic Product (GDP) by 33 to 35 per cent by 2030 from 2005 level.
"The potential to reduce emissions from cement is significant, since a one per cent increase in thermal substitution rate (TSR) will result in reduction of 2-3 kg carbon (CO) reduction/ tonne of cement," says Milind Murumkar, Advisor & Consultant for AFRM.
Alternative fuel use (thermal substitution rate or TSR) increased from 0.6 per cent in 2010 to 3.7 per cent in 2015 and then dropped to 2.7 per cent in 2017, according to the report Low Carbon Technology Roadmap (LCTR) for the Indian Cement Sector: Status Review 2018 released by World Business Council for Sustainable Development (WBCSD).
The upward trend in alternative fuel use tapered off in 2016 and 2017 due to the comparative increase in prices of certain alternative fuels, making them uncompetitive to use instead of conventional fuels. This trend is expected to reverse and climb in the years to come due to improved economics, WBCSD exuded hope. More than 60 cement plants in India have reported continual use of alternative fuels. The sector consumed more than 1.5 million tonnes of alternative fuels in 2015. Biomass is 24 per cent of the total alternative fuel consumed.
Over the years, petcoke consumption has increased steadily in the Indian cement industry, mainly owing to the cost advantage it offers. Coal use (Indian and imported) has been declining over the years, and petcoke and alternative fuels are gradually replacing it. In 2017 the share of coal was 41 per cent while that of petcoke was 56 per cent and alternative fuels was 3 per cent. Changes in the fuel mix have lowered carbon intensity by 2 kgCO2/t cement. The overall emissions factor (for coal and petcoke) decreased to 94.1 kgCO2/GJ in 2017 from 94.7 kgCO2/GJ in 2010.
While terming the TSR in Indian cement industry as remarkably low when compared to the standards of Europe where the AFR substitution rate is more than 40 per cent, Ashok Kumar Dembla, Managing Director & President, Sita Ram Sharma, Head - Parts & Services, both from Humboldt Wedag India say, "There is huge scope for improving the figures that we are clocking today. It needs continuous support from Government and associated bodies. A critically reviewed vision plan to be laid out involving all the stakeholders to target the TSR levels of developed nations."
Picking up pace The concept of co-processing of waste in the cement kilns has been catching up over a period of last 3-4 years. Murumkar attributes this rising use of AFR to the continuously increasing cost of fossil fuels, severely affecting the operating margins of the cement manufacturers, and the regulatory initiatives taken during the recent years.
Regulatory drivers have also accelerated the co-processing of waste by cement companies. The Ministry of Environment Forests and Climate Change (MoEFCC) issued its Solid Waste Management Rules in 2016. These rules give preferential status to the co-processing of waste as a management option. Some state pollution control boards (SPCBs) have approved inter-state transportation of hazardous waste to encourage co-processing. "Together, these have resulted in increasing alternative fuel use," says WBCSD report.
India's cement sector, being one of the eight core energy intensive sectors, is a part of PAT scheme (Perform, Achieve and Trade), launched under the National Mission to Enhance Energy Efficiency (NMEEE). The cement industry has been one of the major contributors to energy reductions in PAT Cycle 1, having surpassed its targets by more than 80 per cent. "Considering that latest technologies for energy reduction including waste heat recovery systems (WHRS), grinding systems etc., which are being widely adopted, one of the main levers to achieve PAT targets in the future is increasing AFR substitution in cement kilns," says Murumkar.
In a BAU scenario, India will require a landfill area of 8,800 hectares by 2050. This is equivalent to the size of the city of New Delhi. By using 25 per cent AFR by 2050 (as per the objectives of the LCTR), the cement industry can contribute to a 26 per cent reduction in the space required for landfilling. About 80 per cent of the estimated 62 million tonnes of MSW generated in India is indiscriminately disposed of in dump sites.
Cement industries can certainly play a key role in promoting better waste management practices and create a win-win situation by working with urban local bodies on waste segregation and management of municipal solid waste. Indian cement plants have used different types of waste as alternative fuels. Solid waste is 73 per cent of total alternative fuel use. The major types of solid waste used are carbon black, tire chips, refuse-derived fuel (RDF), captive power plant (CPP) bed ash and dolachar. Substantial fractions of industrial, commercial, domestic and other wastes contain materials that have the potential for use as an alternative raw material or as a supplementary fuel for energy recovery in cement kilns.
The basic reasons for low TSR can be broadly assigned to lack of knowledge on AFR usage in Indian cement industry in the early years, especially on usage of industrial waste, lack of skilled persons for handling and usage of industrial wastes, lack of proper infrastructure for storage and feeding of AFR materials to cement kilns, lack of proper understanding on the permitting process in regulatory bodies and above all, the will to receive and use the waste materials in cement plants, says Murumkar. In the last two years, remarkable transformation has been noticed on all the above aspects with dramatic changes in the mindset of regulatory bodies, the plant operating professionals and also of waste generators who are shifting to co-processing as a better option over landfilling and incineration as it provides a cost-effective option to them, Murumkar adds.
AFR can be used alone also as fuel in cement kilns. A proper understanding of the processes, raw material characteristics and the waste compositions are the key factors that need to be assessed before use of AFR in a particular kiln system... Actions by all stakeholders are critical for realisation of the vision to become reality. The government and industry must take collaborative action to create a favourable framework for accelerating and implementation of AFR usage in cement plants. "The government should create and enable level playing field for the AFR users by providing interim financial stimulus packages that compensate and provide an edge in pricing pressures. Also, the government should take initiatives to establish the state-of-art waste treatment plants, crop waste processing units etc., in collaboration with cement plants in that particular cluster to supply segregated and treated alternative fuels," say authors of an article for ICR from Humboldt Wedag India.
The main technical barrier is the adverse impact created on kiln production and specific energy consumption. The companies are in the process of developing a complete understanding of the impacts of minor constituents and what effects they might have on long-term cement performance.
For putting latest and innovative technol- ogical change into action, Humboldt Wedag India suggests that all stakeholders should intensify collaborative action to increase the implementation of the state-of-the-art technologies and share best operating practices. "The governments and industry should ensure sustained funding and supportive risk-mitigating mechanisms to promote the development and demonstration of new technologies and processes that offer increase in AFR utilisation."
It has been proven beyond doubt that, in a cement kiln, the organic constituents of fuel are completely destroyed and the inorganic constituents combine with the raw materials and exit as part of the cement clinker without generating solid residues, thus providing the best solution for waste management, says Murumkar.
So, AFR offers twin benefits of benefiting cement companies on one side and managing huge quantities of waste on the other. The government must provide incentives for the use of RDF derived from municipal solid waste and biomass to promote high-volume use of these AFRs for deriving the maximum social benefit.
The industry has set for itself to achieve a 25 per cent TSR target by 2050. For Indian cement plants to increase TSR by 25 per cent (in 2050), a major barrier is cost of material sourcing and acquisition, says WBCSD.
The cost of sourcing the material should be regulated by applying "polluter pays principle" by imbibing the principle among waste generating industries. Higher fuel substitution will take place if waste legislation restricts landfilling and dedicated incineration and allows controlled collection and treatment of alternative fuels. Thus, it is imperative to know that co-processing can offer a local and desired route to manage wastes with minimum liability and environmental impact addressing all the requirements of sustainable development and help reducing our energy demand from natural resources.
- BS SRINIVASALU REDDY