Soils 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.

中文翻译：

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瑞士有机废物中塑料的物质流分析

事实证明，土壤是释放到环境中的塑料的主要储水池。已经确定了几种农业做法，这些做法可能导致大量的塑料流到土壤中，其中包括使用塑料污染的堆肥和消化物。但是，目前尚不清楚这种流量的大小。这项工作的目的是根据瑞士使用物质流分析（MFA）的数据，对堆肥和消化到土壤中的塑料的流动进行量化。该模型的输入数据基于有关有机废物管理和堆肥中塑料含量的公开数据。为了量化生物质输入中的塑料，在厌氧消化设备中进行了测量。连同已发布的有关堆肥中塑料含量的数据，⁻¹的塑料与有机废物一起进入系统，并且6,200吨^-1的年垃圾被清除并焚化。固体消化物中含有34.5±7.1 t年^-1的堆肥，50±11 t年^-1的堆肥，12.4±3 t年^-1的堆肥堆肥和2.0±0.4 t年^-1的共消化固体消化物。总体上，71±11吨年^-1的塑料转移到农业土壤，22.4±3.3吨年^-1到园艺和3.6±0.7吨年^-1私人消费者。我们使用动态MFA预测，自1985年以来，通过添加堆肥，瑞士土壤中已积累了1,390±390吨塑料。这些值可作为评估堆肥对土壤中塑料污染的贡献的基础。