It is now established that the value preserving model of a circular economy is a powerful tool towards a sustainable future. The Indian cement industry with its second largest producer tag contributes to the circular thinking by managing various kinds of waste, be it steel industry slag, fly ash or municipal solid waste (MSW).
Clearly, the Indian cement industry’s demand profile offers an opportunity to be a mega participant in waste management. With production at 298 mtpa in 2017-18 and expectations of over 550-600 mtpa by 2025, the demand profile of raw materials is equally large. To meet numbers like that, the industry would require over 51 million tonnes of coal, definitely a big ask, considering the mineral is in short supply.
Apart from supply issues, the impetus to substitute coal in the production of clinker for cement is imperative, being driven by the government’s Swachh Bharat Mission directive to use alternative fuels and raw materials (AFR). The AFR requirement has therefore built a compelling case for using refuse derived fuel (RDF) along with the industrial wastes that is already a part of kiln feeds.
The thermal substitution rate (TSR) refers to the percentage of sustainable alternative fuels used replacing fossil fuels.
The opportunity RDF offers to enhance the thermal substitution rate (TSR) of cement kilns in the country is substantial. With growth in urban population over the next decade, the opportunities offered by use of RDF also include savings of over a billion rupees (TERI – INR 1052 million) in coal imports. A large chunk of this prospect is driven by the growth in urban population expected in the next decade.
The United Nations (UN) forecasts that the urban population in India will amount to 530 million by 2030, which translates into an addition of 10 million per annum.
Current estimates of the amount of municipal waste produced by the country stands at a whopping 144,165 metric tons per day, according to the Central Pollution Control Board (CPCB). Of this, about 40-60% comprises organic waste. MSW is estimated to be growing at 1.33% per capita per annum led by increasing income profiles and changing consumption behaviour.
The corresponding greenhouse gas emissions are expected to grow from 19 million tCO2e to 41 million tCO2e annually in a business as usual (BAU) scenario by 2030. Responding to the need of the hour, the Cement Manufacturers Association (CMA) took a pledge on World Environment Day in June 2018 to minimise single use plastic in the sector.
Currently, the average TSR in the cement industry has moved up to 4% from less than 1% about a couple of years ago. The industry is now working towards reaching TSR of 25% by 2025 and 30% by 2030.
We will have the potential to consume 12 million tonnes of plastic waste in our kilns annually by 2025, resulting in conservation of conventional fuels such as coal to the extent of 10 per cent.
– CMA President Dr Shailendra Chouksey
RDF derived from municipal solid waste (MSW) which includes material that is combustible in nature but not recyclable such as soiled paper, soiled cloth, contaminated plastics, multilayer, packaging materials, other packaging materials, pieces of leather, rubber, tyre, polystyrene (thermocol) and wood can be used as kiln feed or solid waste based power plants. Solid waste generated in India offers the potential to reduce over 15 million tons of CO2, adding to the Nationally Determined Contributions (NDCs).
NDCs refer to initiatives by participant countries in the Paris Agreement of 2015. The Agreement expects each country to outline and communicate their post-2020 climate actions, known as their NDCs.
Energy from RDF
The enhancement of the thermal substitution rate will require adequate pre-processing infrastructure for RDF, both in terms of quality and quantity that will make it suitable for use in cement plants. One of the alternatives to improving the quality of locally generated RDF would be to blend RDF (which typically achieves an energy value of 1500 kcal/kg) with a better form of RDF known as Solid Recovered Fuel (SRF), which is made from commercial and industrial waste. Co-processing could raise its calorific value to a cement industry specification of 3600 kcal/kg.
Commercially-produced SRF reportedly has an average calorific value of 4700 kcal/kg. Once this is blended in the ratio of 55:45 (SRF:RDF) the resultant blended fuel achieves a consistent calorific value of around 3600 kcal/kg, which would be suitable for firing cement kilns as alternative fuel.
However, a study of major cement clusters has revealed that in about 70% of cement plants, utilising MSW available within a radius of 100 km will be able to achieve a TSR of 0.41% with an assumed calorific value of 2500 kCal/kg.
A TERI study, which offers possible solutions to the 100 km issue, provides tangible advantages of using RDF
- 15.5 million tons of carbon reduction
- 0.52 million tons of fossil fuel like coal or petcoke per annum can be replaced
With about 68 million tonnes of MSW being produced annually, it is ideally possible to generate 6.8 million tonnes of RDF annually potentially translating into 10-15% of TSR. The proposal to expand TSR could be better served with a review of guidelines provided for collection of RDF and exploring alternatives that can help increase substitution rates in cement plants.