Life cycle assessment of compostable plastics: critical review and gap analysis

Bio-based and biodegradable plastics are increasingly considered sustainable alternatives to fossil-based plastics due to their potential for environmental benefits and circularity. However, evaluating their overall sustainability requires assessment of environmental impacts across the entire life cycle to avoid burden shifting and unintended consequences. This study presents a critical review and gap analysis of 63 published life cycle assessments (LCA) studies on bio-based compostable plastics, focusing particularly on compostable plastic and how end-of-life is modelled. The review identifies key data gaps and methodological limitations that affect the accuracy of environmental evaluations. Key findings reveal the inconsistent modelling approaches for composting processes, with significant data gaps concerning the temporal dynamics of CO₂ emissions during biodegradation, the environmental consequences of compost application to soil, and polymer-specific degradation rates that determine the persistence of materials and their potential contribution to plastic leakage. The analysis highlights the need for material-specific life cycle inventory (LCI) data capturing emissions to air and impacts on soil, as well as improved reporting of plastic leakage and microplastic flows, for which inventory methods and characterization factors are increasingly available but remain unevenly applied. Addressing these gaps is essential for improving the reliability and completeness of environmental assessments of compostable plastics.