Field studies on the deterioration of microplastic films from ultra-thin 1 compostable bags in soil

Authors: ACCINELL, CESARE - University Of Bologna, Italy; Abbas, Hamed; BRUNO, VERONICA - University Of Bologna, Italy; KHAMBHATI, VIVEK - Oak Ridge Institute For Science And Education (ORISE); Little, Nathan; Bellaloui, Nacer; SHIER, THOMAS - University Of Minnesota

Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2021
Publication Date: 3/1/2022
Citation: Accinell, C., Abbas, H.K., Bruno, V., Khambhati, V.H., Little, N., Bellaloui, N., Shier, T.W. 2022. Field studies on the deterioration of microplastic films from ultra-thin 1 compostable bags in soil. Journal of Environmental Management. 305:114407. https://doi.org/10.1016/j.jenvman.2021.114407.
DOI: https://doi.org/10.1016/j.jenvman.2021.114407

Interpretive Summary: The use of cornstarch-based bioplastic sheeting in agriculture has increased recently as a more environmentally safe alternative to polyethylene. The findings in this study show that microplastic particles of biodegradable film remain after industrial composting of bioplastic, when it is applied to soil, and that they attract and presumably feed the population expansion of microbes such as Aspergillus flavus, that produce important toxins, in this case aflatoxins. Aflatoxins produced by the expanded populations could contaminate the crops grown in those fields, and thus impact the safety of the food and feed supply. Therefore, it is important to monitor the microplastic levels left at the end of industrial composting operations to prevent this problem.

Technical Abstract: In recent years, some countries have replaced single-use plastic bags with bags manufactured from compostable plastic film that can be used for collecting food wastes and composted together with the waste. Because industrial compost contains uncomposed fragments of these bags, application to field soil is a potential source of small-sized residues from these bags. This study was undertaken to examine deterioration of these compostable film microplastics (CFMPs) in field soil at three different localities in Italy. Deterioration of CFMPs did not exceed 5.7% surface area reduction during the 12-month experimental period in two sites located in Northern Italy. More deterioration was observed in the Southern site, with 7.2% surface area reduction. Deterioration was significantly increased when fields were amended with industrial compost (up to 9.6%), but not with home compost. Up to 92.9% of the recovered CFMPs were associated with the soil fungus Aspergillus flavus, with 20.1% 35 to 71.2% aflatoxin-producing isolates. Application of industrial compost resulted in a significant increase in the percentage of CFMPs associated with A. flavus. This observation provides an argument for government regulation of accumulation of CFMPs and elevation of hazardous fungi levels in agricultural soils that receive industrial compost.