Biodegradation of poly-ε-caprolactone under controlled composting conditions

The biodegradation of the biodegradable plastic poly-epsilon-caprolactone(PCL) was examined by measuring the release of CO2 when the plastic was mixed not with matured compost, as in the conventional method, but with dog food used as a model fresh waste under controlled laboratory composting conditions. From the composting in which the PCL was mixed with the dog food at various ratios, it was found out that the quantity of PCL decomposition, calculated as the difference in the quantity of CO2 evolution in the presence and absence of PCL, was in proportion to the PCL mixing level. It was thus confirmed that the mixing of PCL to the dog food scarcely exhibited any effect of promoting or inhibiting the decomposition of the dog food itself within the mixing ratio employed in this experiment (less than 33% on a dry weight basis) and thus the difference in the quantities of CO2 evolved in the presence and absence of the biodegradable plastic could be regarded as the quantity of CO2 evolution in association with the decomposition of PCL, i.e. the quantity of PCL decomposition. The percentage of PCL decomposition, which is calculated as a ratio of the quantity of PCL decomposition to the mixing level of PCL, was 84% after 11 days in the composting using dog food, but was 59% after the same period using matured compost. Therefore, it was confirmed that a higher PCL decomposition rate was achieved by mixing PCL with fresh waste than by mixing it with the matured compost. (C) 1998 Elsevier Science Limited. All rights reserved.