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Abstract
Global production and consumption of plastics and its deposition in the environment are growing rapidly, while their life-cycle impacts to the environment are yet to be fully understood. This study reviews the existing literature with the goal of evaluating the state of current data and knowledge on plastics’ life-cycle environmental impacts. We identified 98 peer-reviewed journal papers, 25 reports, 8 databases as well as 21 existing reviews on the environmental impacts of plastics. Our review shows that life-cycle approaches have been instrumental in gaining new insights on the environmental implications of plastics. Global life-cycle greenhouse gas (GHG) emissions from plastics, for example, is estimated to be around 1.7 Gt CO2e yr-1, which is substantially larger than the GHG emissions from global aviation. LCAs have also been widely employed in various comparative studies such as biomass v.s. petroleum-based plastics, single-use plastics v.s. multi-use alternatives, which often result in counterintuitive outcomes. However, our analysis also indicates that there still is a paucity of reliable data and tools for conducting LCAs of plastics. In particular, we find that Asia, the major plastic-producing region, is scarcely covered by existing literature and databases. In addition, the life-cycle impacts of plastic additives, and the degradation pathways and associated environmental, human and ecological impacts of plastics are poorly understood, limiting our ability to gauge the life-cycle impacts of plastics. Furthermore, we find that a consensus on the allocation of environmental impacts for the recycling and reuse of plastics is yet to be reached. We identify four major areas of future research including: (1) developing the method for reliable estimate of the amount of plastics entering the environment, (2) understanding plastics’ environmental degradation pathways, degradation byproducts, and their human and ecological impacts, (3) expanding the coverage of life-cycle inventory data across geographies and additives, and (4) building consensus on key methodological issues including those around allocation.