Composting studies of poly (beta-hydroxybutyrate-co-beta-hydroxyvalerate)

The compost activity of poly (beta-hydroxybutyrate) [P(B-HB)] and a copolymer of 20% beta-hydroxyvalerate [P(beta-HB-co-20% beta-HV)] were studied in a simulated municipal solid waste compost test at a constant temperature of 55 degrees C and a constant moisture content of 54%. The goal of this study was to compare the biodegradation rate of the polymer at various time points during the composting cycle as well as to investigate the effect of the acclimation or exposure time of a sample. The test films were divided into two groups. Group one was made up of samples which were exposed to the bioreactor continuously for a total of eighteen days with the sample weight loss being measured at time increments of three days of exposure. Group two was made up of samples which were each individually only exposed to the bioreactor environment for a total of three days but the exposure was at various time points during the composting cycle. Biodegradation was measured through weight loss and normalized for thickness (mu g/mm(2)). The compost activity was found to be divided into three stages with the maximum rate of polymer degradation occurring between the tenth and fifteenth day. Higher degradation rates were observed for the continuously exposed samples. The weight loss of the P(beta-HB-co-20% beta-HV) was found to be significantly faster than that for the P(beta-HB) in this compost test.