EFFECTS OF INTENSIVE MICROBIAL-METABOLISM ON STARCH-FILLED POLYETHYLENE FILMS IN CONTROLLED COMPOSTING WINDROWS

Low density (LDPE) and high density (HDPE) polyethylene films filled w ith starch up to a maximum level of 20% by weight were tested for biod egradation under different environmental conditions. Composting windro ws consisting of various putrescible waste and assembled for controlle d biostabilization management under static conditions were used. The p hysical and chemical deterioration of the polyethylene-starch films ex posed to a controlled composting environment were recorded and analyze d with respect to the different composting evolution and were compared with the data collected in pure culture systems and in bench scale te sts simulating an aerobic biostabilization process. Evidences are pres ented on the partial removal of starch from the different films as a c onsequence of massive surface colonization by various microorganisms. Loss of starch is accompanied by a small but significant drop in the a verage molecular weight and decrement in mechanical strength. In the c ase of a composting trial experiencing prolonged severe temperature co nditions, a small but spectroscopically detectable oxidation of the po lyethylene matrix was also observed. Efficiency of the controlled comp osting systems can be claimed in assessing reproducible conditions in an accelerated biostabilization of putrescible matter and hence versat ility in the evaluation of the degradation of plastic manufacts.