Biodegradation of aliphatic-aromatic copolyesters: evaluation of the finalbiodegradability and ecotoxicological impact of degradation intermediates

The biological degradation behaviour of the aliphatic-aromatic copolyester Ecoflex((R)) was investigated with regard to the degree of degradation and the intermediates formed during the degradation process. The individual the rmophilic strain Thermomonospora fusca, isolated from compost material, was used for the degradation experiments in a defined synthetic medium at 55 d egreesC. After 22 days of degradation more than 99.9% of the polymer had de polymerized and with regard to the degradation of the diacid and diol compo nents of Ecoflex((R)) only the monomers of the copolyesters (1,4-butanediol , terephthalate and adipate) could be detected by gas chromatography/mass s pectroscopy (GC-MS) measurements in the medium. In interrupted degradation experiments predominantly the monoesters of adipic acid and terephthalic ac id with 1,4-butanediol were observed in addition to the monomers. In toxico logical tests with Daphnia magna and Photobacterium phosphoreum no signific ant toxicological effect was observed, neither for the monomeric intermedia tes nor for the oligomeric intermediates. From a risk assessment it can be concluded that there is no indication for an environmental risk when alipha tic-aromatic copolyesters of the Ecoflex-type are introduced into compostin g processes. (C) 2001 Elsevier Science Ltd. All rights reserved.