Akihito Ohtaki*, Nobuyuki Uehara*, Haruo Nishida** and Kiyohiko Nakasaki*

* Department of Materials Science & Chemical Engineering, Faculty of Engineering, Shizuoka University
** Tsukuba Research Laboratory, Tokuyama Co. Ltd.

+ Correspondence should be addressed to Kiyohiko Nakasaki:
(3-5-1 Johoku, Hamamatsu, Shizuoka 432 Japan)

Abstract

Biodegradability of poly-b[beta]-propiolactone (PPL), one of the biodegradable plastics, under thermophilic composting was examined by using a bench-scaled composting apparatus. Since the PPL can be converted to CO2 and H2O when it is completely decomposed by microorganisms, the percentage of biodegradability was obtained by determining the percentage of carbon in the PPL that was converted to CO2 during composting. Quantity of CO2 evolution accompanied with PPL decomposition was estimated by the difference of cumulative CO2 evolution between compostings with and without addition of PPL. The difference in CO2 evolution became larger with the composting progress suggesting that the degradation of PPL occurred at the late stage. Biodegradation of PPL proceeded faster at around 40-50*C[Celsius degeree] than at 60*C[Celsius degeree] when dog food was used as a composting raw material, and approximately 37% of PPL decomposed to CO2 no more than 8 days at the 50*C[Celsius degeree] composting. In addition, biodegradability of PPL was found to be dependent on the kind of seeds used for composting. Furthermore, it was also confirmed that the PPL was degraded ca. 40% for 19 days of thermophilic composting process where garbage was tried to use as a composting raw material instead of dog food.

Key words: waste treatment, plastic waste, composting, biodegradable plastic, microorganisms