Material flow analysis of plastic in organic waste in Switzerland

Abstract

AbstractSoils have been shown to be a major sink for plastic that is released to the environment. Several agricultural practices have been identified that can result in large plastic flows onto soils, among them the use of plastic‐polluted compost and digestate. However, the magnitude of this flow is currently still unclear. The aim of this work was to quantify the flows of plastic with compost and digestate onto soils based on data from Switzerland using material flow analysis (MFA). Input data to the model were based on published data on organic waste management and plastic content in compost. In order to quantify the plastic in the biomass input, measurements were made at an anaerobic digestion plant. Together with published data on the plastic content in compost, the full fate of plastic in organic waste in Switzerland could be obtained from 1985 to 2017. 6,300 t year−1 of plastic enter the system together with organic waste, and 6,200 t year−1 are removed and are incinerated. 34.5 ± 7.1 t year−1 are contained in the solid digestate, 50 ± 11 t year−1 in compost, 12.4 ± 3 t year−1 in windrow compost and 2.0 ± 0.4 t year−1 in solid digestate from codigestion. Overall, 71 ± 11 t year−1 of plastic are transferred to agricultural soil, 22.4 ± 3.3 t year−1 to horticulture and 3.6 ± 0.7 t year−1 to private consumers. Using dynamic MFA, we predict that 1,390 ± 390 tonnes of plastic have accumulated in Swiss soils through compost addition since 1985. These values can serve as basis for evaluating the contribution of composting to the plastic pollution in soils.