Effects of climate and soil properties on the mineralization and disintegration of biodegradable polymers: A meta-analysis

In recent years plastic use in agriculture has led to higher crop yields as well as decreased resources needed to grow crops, such as agrochemicals and irrigation water. However, the complete retrieval of plastics such as mulch films is challenging, leaving plastic fragments in the soil and forming macro-, micro- and nano- plastic residues over time. The sustainability of fully replacing conventional plastics with biodegradable plastics in agriculture is still widely debated due to variable rates of biodegradation which have been observed across various soil and climatic conditions. Understanding which factors control the processes of biodegradation is critical for the development of models to predict the biodegradation of these plastics across various soils.

To this end, we conducted a global meta-analysis of the degradation of biodegradable plastics in agricultural soils. Studies across field, mesocosm and laboratory experimental scales were included to determine which soil, environmental, and polymer parameters are the most impactful on biodegradation rates and how these rates vary across experimental scales. Parameters investigated included but were not limited to temperature, precipitation, land management practices, soil physicochemical properties, polymer surface area, polymer type, and polymer detection methodologies. We found that a large proportion of research on this topic do not report basic soil properties such as soil texture. Despite this shortcoming, we still were able to identify the most relevant soil, environmental, and polymer parameters that affect the biodegradation rates of biodegradable plastics. Results from this meta-analysis will be used in the development of a conceptual process-based fate model to predict the degradation rates and steady-state concentration of biodegradable plastic residues in agricultural soils across various soil types. The development of such model will provide critical information to stakeholders who seek to find alternative biodegradable materials to conventional agricultural plastic products.