Commercial production of accelerated carbonated aggregate from MSWI APCR

The incineration of municipal waste is set to more than double in the UK in the next six years; increasing the percentage of municipal waste managed by this method from 10% to 32%. The scrubbing of the flue gases generates alkaline hazardous air pollution control residues (APCr), which may contain significant trace levels of contaminants, including lead and zinc. The bulk of UK APCr is currently sent to landfill. Its diversion into products with value presents an alternative and more sustainable management strategy. An accelerated carbonation-treatment process has been developed for managing the risks associated with hazardous wastes including APCr. Carbonate-solidified APCr is a stabilised, engineered material that can be used in construction. Waste carbon dioxide gas provides the source of carbon and a lightweight aggregate can be produced. The present work describes the development of a process for manufacturing carbonated aggregates from laboratory scale, through pilot-scale production, to the construction of a full-scale commercial plant. The commercial production plant is currently producing 36,000 tonnes of lightweight aggregate per year from a number of sources of UK ash. The aggregate produced from carbonate-solidified APCr is being used in the manufacture of medium-weight concrete blocks.