What happens to waste-to-energy incineration ash?

Fly ash—or air pollution control residue (APC)—consists of the hazardous and fine particulates removed from a WtE plant’s flue gas, the fumes produced from incineration. Fly ash generally undergoes treatment to reduce its negative environmental impacts, largely in the form of air and water pollution of nearby ecosystems. While there are efforts to recycle and reuse fly ash, it’s commonly sent to hazardous waste landfills.

Bottom ash—or incinerator bottom ash (IBA)—is all ash left over that is not fly ash. It consists mainly of silica, calcium, iron oxide and aluminum oxide. Large magnets can remove some of these materials for recycling and repurposing. For example, construction companies might use bottom ash to make concrete or bulk fill. The rest is sent to landfills.