Utilization of Alternative Fuels in Cement Pyroprocessing : the Messebo Factory case study in Ethiopia

Energy costs and environmental standards encouraged cement manufacturers worldwide to evaluate to what extent conventional fuels (Furnace oil, Coal and Petcock) can be replaced by alternative fuels in cement production, i.e. biomass or processed waste materials like sewage sludge, MSW (municipal solid waste), Refuse Derived Fuels (RDF), Tire Derived Fuel (TDF), Plastic Derived Fuel (PDF), Biomass Derived Fuels (BDF), meat and bone meal (MBM), etc. High temperature of >1500 C, long residence times of up to 10 seconds and high turbulence in the cement kiln ensure complete destruction of organic constituents in the waste materials. The main benefits of using solid alternative fuels in cement kilns include enhanced energy recovery and conservation of non-renewable fossil fuels which in other words translates into an immediate reduction of greenhouse gas emissions related not only to conventional fuel mining and utilization but also helping the cement industry to clear its image of being among the most polluting and CO2 emitting industries. Most notably, a reduction in cement production costs is also expected. Varying amounts of different alternative fuels have been studied in this thesis and referred to an actual cement plant in Ethiopia, located in the northern province of Mekelle. The availability of alternative fuels in the region has been estimated. Calculations have been performed for the comparison with the reference case for each alternative fuel option. Possible technical challenges in the combustion process and the supply feed chain as well as in the resource base have been identified. The environmental benefits for the reference plant and the impact on cement costs have been evaluated and discussed. The results show a clear advantage for alternative fuel utilization, both in terms of environmental parameters and also in production costs for the cement plant.