Composting organic residues: trace metals and microbial pathogens

Industrialized societies are responsible for increasing environmental pollution by trace metals, and pathogenic micro-organisms associated with products and wastes of industrial processes and agricultural production, as well as household activities. The objective of this paper is to discuss the effect of composting on the behavior of trace metals and pathogenic micro-organisms, and to present the latest finding on sanitizing and stabilizing organic fractions and trace metals in composted biosolids. Evidence provided by long-term scientific studies in North America and Europe on toxic effects of trace metals on soil micro-organisms and on pathogenic micro-organisms suggests that revisions of the current guidelines on sludge applications on agricultural soils are needed to protect long-term soil fertility. In addition, the antagonism between harmful characteristics of biosolids and their usefulness for agriculture and land reclaiming purposes could be mitigated by using efficient composting treatments. The production and use of harmless organic wastes should be one of our highest priorities in order to protect our health and environment, and to hand over a sustainable agriculture to future generations.