For bioplastic materials to be accepted in composting plants, biodegradability alone is not sufficient. As important is the disintegration during composting. This is the physical falling apart of the bioplastic material, or more precisely of the product that has been made from it, into fine visually indistinguishable fragments at the end of a typical composting cycle. The property of disintegration is measured in a pilot-scale or full-scale composting test. The test substance is subjected to a spontaneous composting process for a duration of 12 weeks. At the end, a sieving over 2 mm followed by a precise sorting analysis is executed. It may be that a bioplastic passes the test at a specific thickness but fails the test at a higher thickness. It must also be demonstrated that the bioplastic materials have no negative effect on compost quality. This involves chemical analyses, e.g. heavy metals, required to evaluate conventional compost quality. In addition, ecotoxicity tests are advised, including plant germination tests as well as animal toxicity tests. The purpose of these tests is to make sure that small additives (e.g. in the <1% range) falling beyond the sensitivity of biodegradation tests as well as metabolites from biodegradation do not exert any negative biological effect. Technical aspects include the compatibility of pre-and posttreatment in a compost plant to the inclusion of bioplastics in the compost feedstock. The most important aspect is to schedule sieving at the end of the composting cycle. (C) 1998 Elsevier Science Limited. All rights reserved.
