ABSTRACT
Soils heavily polluted with metals are common in and around industrial areas where mining, processing and smelting of ores have taken place. The concentrations of metals like cadmium, (Cd), copper (Cu), lead (Pb) and Zinc (Zn) may be so high that it is dif—cult to establish plants on these soils to prevent erosion and spreading of pollutants by wind and water. In polluted areas surrounding such industrial sites, crop plants grown on less contaminated soil may grow well, but become too rich in heavy metals to be suitable as food or feed. Alternative soil use, like cultivation of nonfood crops (e.g., —bers or bioenergy), may be a solution, but often the metals contained in such crops will cause problems later in their life cycle. Two solutions then remain: to use biotic or abiotic amendments that reduce metal uptake in plants, or to use amendments that enhance metal uptake, in order to collect aerial plant parts and treat this biomass as hazardous waste. In the latter case, if the ashes are collected and the fumes treated properly, the biomass can still be used for, e.g., bioenergy. This provides a gain from the crop, removes pollutants from the soil and reduces the volume of metal rich waste. The fact that light ash fractions commonly contain more metals than heavy ash fractions (Vervaeke et al. 2006) can be used to treat these ash batches differently, possibly recycle metals in some cases, and further reduce the costs of special treatments.
