Overlooked Risk of Microplastic from Kitchen Waste Short Stacking Phase

Current research on microplastics (MPs) in kitchen waste primarily focuses on their end-of-life disposal processes, neglecting the rapid decomposition phase prior to disposal. This study investigated MPs’ instantaneous release during a 20 h kitchen waste stacking process. The results revealed significant temperature-dependent release, with up to 96.1% entering the liquid phase and 5768 items/kg released and with an average of 85.7% of the MPs transferring into the entrapped water released from the tiny tissue structures and membranes. These MPs were primarily in small sizes (4–400 μm) as particles and fragments. Hydrolysis acidification primarily influences MPs’ release, with temperature and stacking time as intermediate factors. Acetic acid drives MPs’ release, contributing up to 38.5%. High temperatures accelerate organic matter dissolution and MP migration, while low temperatures slow down the release of MPs. The findings confirmed MPs’ release risks during kitchen waste stacking and contributed to optimize kitchen waste management to control MP pollution at its source.