Cement, Energy and Environment

materials content; § possibilities to improve the qualities of raw materials by further processing The available raw materials include use of electric arc furnace (EAF) slag, using fly ash, using slag and carbide slag as an alternative to the existing raw materials. CO use: algae capture and 2 fuel production, biofuels Being the second highest emitter of CO in the world, 2 provides the cement industry a high scope for carbon capture and use. CO can be captured 2 from flue gas streams released from cement plants or their captive power plants and be used as a source of microalgae cultivation . Microalgae, water-based organisms, grow in freshwater, seawater or wastewater through photosynthesis in the presence of light, CO , water 2 and mineral salts. These can be further harvested, dried and used as either a renewable fuel thus substituting fossils like coal, or processed into animal feed, antioxidants, which bear a higher market value. Biogas from microalgae can be supplied as heat or electricity back into the processes, while biomass left after extraction of biogas can be used in the production of chemicals or animal feed. CO 2 emissions of the cement plant was reduced by 4,800 t/year (Cement Sustainability Initiative, ECRA, 2017). Depending on the characteristics of microalgae, space requirement for such an intervention in a best available technology cement kiln with an annual clinker production of 1 million tonne/year would be high. Therefore, microalgae has been cultivated and used at a small scale in cement industries in Sweden, Turkey, France, Canada, Brazil, Portugal, etc.. Use of alternative fuels A mounting problem for the world, waste management is a serious issue for developing nations like India too. The country ranks 10 in the th generation of municipal solid waste, discarding 0.6 million tonnes of plastic waste into oceans and 1.7 million tonnes of electronic and equipment waste annually (Bhatia, 2017). Nearly 74.6 lakhs of hazardous waste are generated in India annually, increasing at a rate of 2-5% per year. Approximately, 10-15% of industrial waste generated is hazardous in nature (Dutta, 2017). Being resource and energy intensive, the cement industry provides a major opportunity to reduce its cost and environmental impact through co-processing of waste; this not only reduces burden on the waste treatment plants but also alleviates additional operational costs of cement industry. Since the industry is characterized by high energy thermal process with temperatures reaching over 0 1,450 C, burning of waste in its manufacturing plants becomes viable. Materials like waste oil, disposed tyres, plastics, auto- shredded residues and sewage sludge are a few waste products to substitute traditional kiln fuels like coal, gas and oil (Baidya, 2016). An advantage of such substitution is that it precludes the need of investing in additional incinerators or landfill facilities to accommodate waste. Moreover, co-processing increases the overall energy use per tonne of clinker produced in the kiln. Many categories of waste, which cannot be recycled easily, have the potential to be sent to cement plants for further use. While high temperatures destroy the organic components in municipal solid waste and sewage sludge, they only disintegrate the metal concentrations, thereby incorporating the metal remains in end product. This can change metal concentrations in cement relative to the final product which does not undergo co- processing. Therefore, national and international standards 11