Unchalee Suwanmanee

Biodegradable kinetics of plastics under controlled composting conditions.

This study models and evaluates the kinetics of C-CO(2) evolution during biodegradation of plastic materials including Polyethylene (PE), PE/starch blend (PE/starch), microcrystalline cellulose (MCE), and Polylactic acid (PLA). The aerobic biodegradation under controlled composting conditions was monitorated according to ISO 14855-1, 2004. The kinetics model was based on first order reaction in series with a flat lag phase. A non-linear regression technique was used to analyze the experimental data. SEM studies of the morphology of the samples before and after biodegradation testing were used to confirm the biodegradability of plastics and the accuracy of the model. The work showed that MCE and PLA produced the high amounts of C-CO(2) evolution, which gave readily hydrolysable carbon values of 55.49% and 40.17%, respectively with readily hydrolysis rates of 0.338 day(-1) and 0.025 day(-1), respectively. Whereas, a lower amount of C-CO(2) evolution was found in PE/starch, which had a high concentration of moderately hydrolysable carbon of 97.74% and a moderate hydrolysis rate of 0.00098 day(-1). The mineralization rate of PLA was 0.500 day(-1) as a lag phase was observed at the beginning of the biodegradability test. No lag phase was observed in the biodegradability testing of the PE/starch and MCE. The mineralization rates of the PE/starch and MCE were found to be 1.000 day(-1), and 1.234 day(-1), respectively. No C-CO(2) evolution was observed during biodegradability testing of PE, which was used for reference as a non-biodegradable plastics sample.

Assessment of Greenhouse Gas (GHG) Emissions of Polylactic Acid (PLA)/Starch and Polyethylene Terephthalate (PET) Trays

This study aims to assess greenhouse gas (GHG) emissions of Poy(lactic acid) (PLA) with cassava starch blend (PLA/starch) and Poly(ethylene terephthalate) (PET) trays from cradle to grave. The various waste treatment scenarios were considered. The functional unit is specified as 10,000 units of 8 x 10 x 2.5 cm. of PLA/starch and PET trays which weigh 597.6 and 582.7.5 kilograms, respectively. The results from cradle to production gate were found that GHG emissions of PLA/starch has 51.38% lower than that of PET. This is because PET has higher weight of the trays. The resin production stage of PET tray has the highest of greenhouse GHG emissions. The results from cradle to grave show that the highest total GHG emissions are observed from PLA/starch or PET trays with 90% of landfill and 10% of incineration. The lowest GHG emissions from disposal PLA/starch and PET trays are from landfill with biogas recovery and incineration with heat recovery. This can be reduced GHG emissions by 3.11103 and 1.28103 kg CO2 equivalent.