Degradation of Compostable Plastics - Danielle Bellmer, Food Process Engineer
Concern about plastic pollution has spurred interest in biodegradable plastics. Many new products exist, but most won’t break down in a landfill; they require a commercial composting environment to degrade properly. One problem is that not many commercial compost facilities exist. Another problem is that many commercial composters don’t want to deal with the ‘compostable’ plastics because they are difficult to handle, and they have a slow and incomplete degradation process. The long-term goal of this project is to develop a pretreatment process for compostable plastics that will make them a welcome addition to commercial compost facilities. The pretreatment could be done locally, before the waste is taken to a regional compost facility.
Work continues on evaluation of the compost process parameters that will help increase the rate of degradation of compostable PLA (Poly lactic acid) coupons. Laboratory compost trials are being conducted in both 250 ml flasks and in 6 L compost vessels, each in controlled temperature environments. Parameters being evaluated include heat pretreatment of the plastics, C/N ratio in the compost substrate, and different compost substrates, including spent mushroom compost. Results show that the PLA coupons disintegrate completely in all treatments, but at different rates. Time of breakdown varies from about 24 to 45 days, with the fastest rates corresponding to both heat pretreatment and added inoculum. Future work will include evaluation of images of some of the samples using scanning electron miscroscopy.
