From waste to alternative fuel
M unicipal solid waste (MSW) is one of the high potential wastes to be used as a fuel for energy production due to extremely large quantity with low cost. The production of refuse-derived fuel (RDF) from MSW is an interesting alternative to the use of high calorific portion of MSW as fuel for energy production.
MSW can be used as co-fuel for biomass power plant or as a substitute fuel in industrial boiler and co-processing in cement industry. This helps to solve the problem of waste management and conserve energy, while reducing environmental impact and greenhouse gas (GHG) emissions.
The light combustible fraction (like paper, biomass, textiles, etc.) separated from the MSW is generally called RDF fluff. It will have a calorific value in the range of about 2,200 to 3,000 kcal/kg with 15 to 20 per cent moisture. About 28-35 per cent of RDF fluff is estimated to be generated from the dry segregated MSW. The material received after pre-segregation/sorting with greater than 100 mm size contains mostly combustible materials. Before sending for final preparation of RDF, the material will be stored in the RDF storage area.
RDF storage, processing and handling
Once sorted, the material is loaded and sent for RDF storage area after weighing. The storage is to be carried on the impermeable layer (i.e.; RDF storage facility) as the waste contains high moisture content and produces leachate. After storage of RDF, material is sent to RDF processing plant for further processing. RDF process includes:
- Density separation.
- Baling and fluff
- Packing and dispatch
This RDF is being co-processed in the cement industry. The cement industry kiln is capable of burning the MSW - RDF. Since the cement kiln has high-residence time and the high temperature range is around 1,200 to 1,500 degree Celsius, this will ensure 100 per cent combustion of RDF. Thereby, the vent out gas will contain less pollutant and it will meet the specifications stipulated by the regulator. All cement industries stack emission monitoring by CEMS and report is connected online to the respective SPCB.
In the current financial year, Ramky Enviro Engineers Ltd has dispatched around 20,000 MT of RDF from its Hyderabad site to various cement industries. The below-mentioned specifications are maintained uniformly to have better fuel efficiency. Specifications of RDF is sent to the cement industry as a fuel:
1.Gross calorific value to be maintained, i.e., 2,300 to 3,200 Kcal/Kg
2.Moisture content below 20 per cent
3.No metals or earth material which poses serious threat to the shredder and the cement factory kiln
4.Un shredder size above 200 mm thickness
5.Secondary shredder size reduction below 100 mm thickness
6.Chlorine <1.5 per cent
As per the Solid Waste Management Rule 2016, mentioned in Definition 38, RDF can be used by the cement industry as a better fuel source. This can replace the fossil fuel as an endangered source in nature. Moreover, the fossil fuel is the major source of greenhouse gas emission.
Methane is a particular potent greenhouse gas. Emission from the fossil fuel is the major source. The global warming potential of methane gas is 25 times than that of carbon dioxide, the methane emitting from land fill is huge and could create a havoc to the atmosphere. By using RDF, the potent air pollutant can be reduced drastically.
By reducing 1.6 kg of carbon dioxide by using per kilogram of RDF, a holistic MSW has a positive consequence on greenhouse gas emission derived fuel. European countries like Netherland, Switzerland and Norway use more than 83 per cent of MSW RDF for co-processing. In India, the RDF utilisation is below 1 to 1.5 per cent of the huge available source.
In cement production, the fuel cost is about 30-40 per cent. By using RDF, the fuel cost will be reduced drastically. A long way is required to replace RDF as a fuel source in Indian context. The cement industry can play an important role in the urgent global need for destruction of MSW to the greater extension. Due to the availability of huge quantity, the cement industry should come forward to use RDF, thereby huge fuel cost can be saved.