Predicted Growth in Plastics Entering Biosolids and Agricultural Lands Exceeds Efforts to Control Source Emissions

Plastic production and consumption have increased exponentially since the latter half of the 1900s. With this has come an extensive release of plastics into every environment on earth. Municipal sewage, for which the solids (biosolids) are recovered and widely used as fertilizers on agricultural lands, is a source of plastics inadvertently and potentially accumulating in soils. Following on from our previous work estimating plastics in Australian sewage biosolids from 1970 to 2016, we estimated and extrapolated the annual global release of plastics to agricultural lands via biosolids application from 1970 to 2050. We show that plastics entering the environment from biosolids increased from an annual 6 metric tonnes (Mt) in the year 1970 to 472,600 Mt in 2021. Extrapolating to 2050, we estimated a global release of around 584,250 Mt annually, for a cumulative global total from 1970 to 2050 of 37 million Mt released to biosolids, 18 million of which to land for agricultural purposes. This was equivalent to 340 g of plastics entering biosolids annually per person in 2021. Identifying and controlling plastics at the source or removing plastics from waste streams is an important focus for reducing contamination in biosolids end-use applications for a circular economy.