Environmental Performances and Energy Efficiency for MSW Gasification Treatment

For the final treatment of municipal solid waste (MSW), thermal disposal by incineration is the dominant technology to obtain energy from the material. In recent years, pyrolisis and gasification technologies have emerged, with the aim to increase energy output and to reduce environmental impact. While biomass pyrolisis and gasification are well known systems and technology of biomass gasifiers is sufficiently advanced, large scale MSW plants-characterized by high gasification efficiency and high energy recovery-are not so widespread. It must be considered also that MSW gasification can be cost competitive in comparison with combustion, besides the potential for better environmental performance. The purpose of this study is, after an analysis of the state of the art of this technology, to compare combustion process with pyrolisis/gasification process, by analyzing the following aspect: feasibility, waste gas emissions and energy recovery. The main results obtained highlight that gasification can be considered a really competitive technological alternative to incineration. From the point of view of the energy efficiency, the direct combustion of MSW seems to grant higher power productions if compared to syngas recovery. Only co-firing of syngas in large power plants or the use of combined cycle gas turbine might give better energy efficiency results, anyway the use of gas engine and gas turbine for syngas recovery could allow very good fuel utilization rates. With regards to air emissions, plants based on all the technologies in connection with a conventional steam boiler and steam turbine cycle can largely meet the emissions limits.