The effect of livestock manure composting on the degradation of polylactic acid (PLA)

This study focused on expanding the environmentally friendly applications of livestock manure by investigating the condition of compost piles when polylactic acid (PLA), a biodegradable plastic material, is used in the composting process.Livestock manure has long been used for organic fertilizer and soil improvement, and recently, biodegradable plastics like PLA, which decompose efficiently in high-temperature environments, have noted as a place where environmental benefits will arise.When shredded PLA particles were added at approximately 8% by volume (23%/dry matter) to a 2.5-ton livestock manure mixture, the compost piles did not show decreased heating compared to the control pile without PLA.However, the treatment pile with PLA particles exhibited higher levels of odorous gases such as ammonia.The total microbial count per gram was slightly higher or significantly higher (p<0.05) in the treatment pile compared to the control pile.The rate of PLA particle degradation was assessed by counting the number of particles, showing a 44.1% reduction after 30 days and a 73% reduction by the end of the 100-day trial.This study examined the impact of PLA on livestock manure composting at a field level and suggests the need for further research on unexplored factors, as well as the possibility of environmental benefits of using PLA as a composting material.