The availability and binding of heavy metals in compost derived from household waste

Organic waste can be recycled as compost which has traditionally been used as a soil improver. As more waste is recycled as compost, it is becoming in creasingly important to find alternative uses for compost. Leachability dat a are used to determine the environmental availability of Cd, Cu, Pb, and Z n contained in natural compost. Batch sorption data are used to determine u ptake of additional Cd, Cu, Pb, and Zn by compost and assess its potential use in remediation work, as an alternative to natural materials such as pea t. The relative binding of these additional metals to compost is found to b e in the order Pb > Cd approximate to Cu > Zn. The sorption of metals on co mpost takes place, at least in part, by exchange of calcium bound to the co mpost and there is evidence that the sorption occurs in both humic and non- humic sites in the compost. The use of compost to bind metals in remediatio n work is discussed. (C) 1999 Society of Chemical Industry.