7.3.3 Fuel switching, including the use of waste materials
While some industrial processes require specific fuels (e.g., metallurgical coke for iron ore reduction), many industries use fuel for steam generation and/or process heat, with the choice of fuel being determined by cost, fuel availability and environmental regulations. The TAR (IPCC, 2001a) limited its consideration of industrial fuel switching to switches within fossil fuels (replacing coal with oil or natural gas), and concluded, based on a comparison of average and lowest carbon intensities for eight industries, that such switches could reduce CO2 emissions by 10–20%. These values are still applicable. A variety of industries are using methane from landfills as a boiler fuel (US EPA, 2005).
Waste materials (tyres, plastics, used oils and solvents and sewerage sludge) are being used by a number of industries. Even though many of these materials are derived from fossil fuels, they can reduce CO2 emissions compared to an alternative in which they were landfilled or burned without energy recovery. The steel industry has developed technology to use wastes such as plastics (Ziebek and Stanek, 2001) as alternative fuel and feedstock’s. Pretreated plastic wastes have been recycled in coke ovens and blast furnaces (Okuwaki, 2004), reducing CO2 emissions by reducing both emissions from incineration and the demand for fossil fuels. In Japan, use of plastics wastes in steel has resulted in a net emissions reduction of 0.6 MtCO2-eq/yr (Okazaki et al., 2004). Incineration of wastes (e.g., tyres, municipal and hazardous waste) in cement kilns is one of the most efficient methods of disposing of these materials (Cordi and Lombardi, 2004; Houillon and Jolliet, 2005). Heidelberg Cement (2006) reported using 78% waste materials (tyres, animal meal and grease, and sewerage sludge) as fuel for one of its cement kilns. The cement industry, particularly in Japan, is investing to allow the use of municipal waste as fuel (Morimoto et al., 2006). Cement companies in India are using non-fossil fuels, including agricultural wastes, sewage, domestic refuse and used tyres, as well as wide range of waste solvents and other organic liquids; coupled with improved burners and burning systems (Jain, 2005).
Humphreys and Mahasenan (2002) estimated that global CO2 emissions could be reduced by 12% through increased use of waste fuels. However, IEA (2006a) notes that use of waste materials is limited by their availability, Also, use of these materials for fuel must address their variable composition, and comply with all applicable environmental regulations, including control of airborne toxic materials.