Combustion of Municipal Solid Waste (MSW) is an important part of the waste management system in many countries. In addition to the recovered energy as heat and power, the combustion gives other advantages, i.e. a large reduction of the waste volume and destruction of toxic organic compounds and pathogens. Emissions of gaseous pollutants, such as HCl, NOx, SO2 and dioxins are restricted and minimized by existing technologies. However, the MSW contains a number of metals in different forms and these end up in the ashes. Depending on the extent of waste sorting the ashes will contain more or less of metals in various forms. The content of, for example, copper and zinc can be comparable to or even higher than the concentrations in ores considered economically feasible for mining. In addition, MSW ashes contain many metals of high value and metals that are considered as critical for the industry. In many countries the only option for MSW ash is landfilling or use as construction material on landfills. Consequently, metals that should be recirculated to the industry are hidden in landfills from where it will be difficult to recover them later on. A group at Chalmers University of Technology presently investigates processes for recovery of copper and zinc from municipal solid waste incineration ash. The processes are primarily based on acid leaching of the ash combined with selective solvent extraction and electrolysis. The work on recovery process development is supported by investigations of the chemical speciation of metals, i.e. identification of metal compounds, in ashes by, for example, synchrotron based X-ray absorption spectroscopy (XAS). The presentation will give an introduction to the chemistry of MSW ashes and speciation results for Cu and Zn, and discuss the promising results that have been obtained using the suggested recovery processes for these metals.

Resource recovery from municipal solid waste ash

247th National Meeting (2014)

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