Biodegradability in Soil and Composting of Microbial Polyester

A petri dish burial test was carried out with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) [P (3HB-co-3HV)] films at 25°C in 11 kinds of soils and one mature moist compost preparation. The rate of biodegradation of the films was strongly dependent on the soil textures. The fastest rate of soil was 100% weight loss of the film at 50 days, while the slowest rate of soil was 20% at 3 months. Relationships between this test, the field testing at the collecting places of 9 kinds of soils and other factors were investigated. The degrading films seemed able sometimes to remain in soils for one year or more depending on the properties of soils and the environment. Next, the garbage with 3% addition of P (3HB-co-3HV) bags was applied to the composting verification test plant. It was found that P (3HB-co-3HV) bags were able to compost with garbage. It was confirmed that shredded P (3HB-co-3HV) bags did not prevent garbage from aerobic fermenting and composting; thus the material was degraded and became invisible to the naked eye in approximately 10-20 days.