Comparison of Two End-of-Life Options for Post-Consumer Polylactic Acid (PLA) Waste.

Municipal solid waste (MSW) management is a costly necessity. Petroleum-based plastics are commonplace in MSW of modern, throwaway societies. Petroleum-based plastics do not breakdown from natural processes in landfills and take up large amounts of valuable space. Compostable plastics offer a sustainable solution to petroleum-based plastics. Polylactic acid (PLA) is a plastic made from 100% renewable resources, is compostable at industrial composting conditions (high heat, high moisture) and also easily breaks down in a recycling process. Published research describing responsible waste management of PLA waste is scarce. This research compares two end-of-life options of PLA: industrial composting and chemical recycling. To test industrial compostability, PLA products were composted in a controlled environment in two separate experiments. The preliminary study shows that PLA composted at 50°C successfully degraded an average of 97% (weight loss) after 120 days, while PLA composted at 40°C did not successfully degrade after 120 days. Compost containing degraded PLA was then applied to plants and physical and nutrient analyses were performed. A more thorough composting experiment was then performed using controlled conditions at 55°C and 60% moisture comparing the degradation effects on 5, 10, 20 and 30 % (by weight) additions of PLA cups vs. paper cups. All PLA treatments degraded over 99% after 12 weeks. Paper treatments did not show consistent breakdown with average weight loss of -19.4, 25.38 and 67.89% for the 5, 10 and 20% treatments respectively. A subsequent germination trial will evaluate the effects of this compost on plant growth. Composting of PLA will be compared to chemical recycling of PLA. Industrial rinsing methods for chemical recycling of post-consumer PLA will be assessed. The University of Wisconsin-Stevens Point (UWSP) currently implements PLA plastic ware at dining facilities on campus. Collection for chemical recycling has been implemented, titled the FRESH project, and is being evaluated by the WI Institute for Sustainable Technology. Post-consumer waste from this project is being used to test for industrial rinsing method effectiveness on the lactic acid product.