Biodegradability of degradable plastic waste

摘要

Plastic waste constitutes the third largest waste volume in Malaysian municipal solid waste (MSW), next to putrescible waste and paper. The plastic component in MSW from Kuala Lumpur averages 24 percent (by weight), whereas the national mean is about 15 percent. The 144 waste dumps in the country receive about 95 percent of the MSW, including plastic waste. The useful life of the landfills is fast diminishing as the plastic waste stays un-degraded for more than 50 years. In this study the com-postability of polyethylene and pro-oxidant additive-based environmentally degradable plastics (EDP) was investigated. Linear low-density polyethylene (LLDPE) samples exposed hydrolytically or oxidatively at 60 deg C showed that the abiotic degradation path was oxidative rather than hydrolytic. There was a weight loss of 8 percent and the plastic has been oxidized as shown by the additional carbonyl group exhibited in the Ecu-' rier transform infra red (FTIR) Spectrum. Oxidation rate seemed to be influenced by the amount of pro-oxidant additive, the chemical structure and morphology of the plastic samples, and the surface area. Composting studies during a 45-day experiment showed that the percentage elongation (reduction) was 20 percent for McD samples [high-density polyethylene, (HOPE) with 3 percent additive] and LL samples (LLDPE with 7 percent additive) and 18 percent reduction for totally degradable plastic (TDP) samples (HOPE with 3 percent additive). Lastly, microbial experiments using Pseudomonas aeroginosa on carbon-free media with degradable plastic samples as the sole carbon source, showed confirmatory results. A positive bacterial growth and a weight loss of 2.2 percent for degraded polyethylene samples were evident to show that the degradable plastic is biodegradable.