COMPOST QUALITY - PHYSICAL CHARACTERISTICS, NUTRIENT CONTENT, HEAVY-METALS AND ORGANIC-CHEMICALS

Bio- and yard waste composts show a high standard of quality. Due to t heir valuable characteristics it is possible to utilize them in plant production. Average heavy metal contents of bio- and yard waste compos ts is low. Nevertheless, the results presented reveal that nine biocom posts do not comply with the requirements necessary to obtain the ''se al of approval for quality compost''. A first check of the data sugges ts that soil contamination of geological, respectively pedological ori gin, is responsible for limit violation. Other limit violations are du e to increased soil contaminant levels, caused by anthropogenic activi ties. Increased heavy metal contents in two more composts is likely du e for above average degree of undesirable materials in the separately collected organic refuse. Dioxins can be found ubiquitously in the env ironment, consequently therefore in composting raw material and in the end product. According to current knowledge, levels of PCDD/F found i n bio- and greencompost can be classified as low. It is recommended to urgently standard use the separate collection and processing methods of bio- and yard waste compost to minimize the introduction of organic trace contaminants. This is the most efficient way to reduce the intr oduction of contaminants. Furthermore, it is urgently demanded to elim inate all sources of dioxins and PCB, such as specific thermal process es (e.g. cable pyrolysis) and chlorinated chemicals (e.g. PCP), to pre vent the further addition of these substances. Irrespective of the cur rent contents of organic trace contaminants in compost, there is gener ally a considerable need for research in the field of contaminant tran sfer (soil-plant; plant-animal; animal-human being) and in the field o f contaminant metabolism, both in the soil and during the composting p rocess. Further knowledge is also needed with regard to their formatio n and origin.