Microplastics in sewage sludge and municipal solid waste

Abstract

Sewage sludge comes from wastewater treatment, whereas municipal solid waste comprises a broad range of non-liquid waste materials from households, businesses, and institutions. Both share similarities in composition, origins as waste products, and in their final use. Biosolids are the stable form of sewage sludge, while the organic fraction of municipal waste can be useful after being composted. The agricultural application of biosolids and composted organic wastes offers an appealing approach to sustainable agriculture, enriching soil fertility, enhancing water management, and reducing wastes. However, although soil amendment with wastes offers numerous benefits, their usage must be carefully managed to prevent any potential risks to the environment and human health. Regulations and guidelines are in place to ensure the safe handling of biosolids and composted fractions, but none of them is still considering the presence in them of microplastics (MP). The incorporation of MPs into soil matrixes may induce alterations in physical, chemical, and biological soil properties. It has also been shown that MPs can release a wide range of additives and may interfere with the fractionation and distribution of pollutants including trace metals. There is an urgent need to limit the dispersion of MPs due to the agricultural use of biosolids and the composted fraction of organic municipal waste. Especially the latter, due to their high production volume and higher plastic content compared to biosolids. Only by harnessing the potential of organic wastes, can agricultural systems move closer to achieving resource efficiency, and long-term productivity while contributing to sustainability goals.