Mechanical heat treatment of municipal solid waste

To meet the requirements of the EU landfill directive, which prohibits the disposal of waste to landfill without prior treatment, various types of waste management processes have been proposed. This paper describes the detailed investigation and analysis of a plant employing a process known as mechanical heat treatment. The plant was built, operated for a pilot period and monitored as part of Defra’s new technologies demonstrator programme. The plant treated 20 500 t of household residual waste, through a combination of heat treatment and mechanical separation technology, to produce solid recovered fuels and recyclables (glass, plastics, ferrous and non-ferrous metals). It is shown that mechanical heat treatment can be an effective and efficient way of processing mixed municipal solid wastes, but the details of the plant and process are crucially important. Modifications to the plant were made as a result of experience gained during the initial phase of operation, including the redesign of some of the equipment to avoid fouling by textiles and plastic film, and the introduction of an additional shredder. Comparison of mass and energy balances for the plant at the beginning and end of the operational period, after improvements had been made, demonstrates an increase in the rate of throughput of waste, significant improvements in the recovery of recyclable materials and fuel products, a reduction in the amount of residual material being sent to landfill and a reduction in the process energy used.