Effect of degradable microplastics, biochar and their coexistence on soil organic matter decomposition: A critical review

Biodegradable plastics often degrade into microplastics within the natural environment, where they interact with soil organic matter (SOM). Concurrently, biochar is applied to soil as a photosynthesis-derived negative carbon technology. However, the efficacy of biochar in carbon sequestration may be compromised by the priming effect triggered by the presence of degradable microplastics. This review critically examines the interaction between degradable microplastics and soil organisms and their collective impact on SOM dynamics. It synthesizes current knowledge on the influence of biochar and degradable agricultural films on SOM, the mineralization processes of degradable microplastics, and the resulting stability of SOM. Special attention is given to the priming effect induced by microplastics and the implications of their coexistence with biochar on SOM decomposition. The review underscores the need for further research to elucidate the long-term carbon budget implications of biochar application and the fate of microplastics on carbon pools within biochar-amended soils.