Carbon reduction of plastic’s circular strategies: tracking the effects along supply chains with waste input–output modeling

摘要

Plastic is a material associated with various Greenhouse Gas (GHG) emissions along the life cycles of different products. Many economies have adopted or planned for strategies to reduce, reuse, and recycle plastic goods and materials. The benefits of reductions in waste generation and GHG emissions need to be evaluated for setting the priority to select policy instruments for managing various plastic materials, products, and wastes. Several studies have made evaluations for the circulation of plastic using different models. However, many models for the circular economy focused on the effect on the macroeconomy rather than the detailed supply chain effects of an individual policy proposal. The reason could be the lack of an environmental assessment model with sufficient clear resolutions in the sectors, waste types, and waste treatments. In addition, the structure of the models limits many studies in modeling the scenarios diverting end-of-life products from waste treatments to recycling and reuse as secondary materials. To bridge this gap, this study adopted the waste input–output analysis methodology and compiled the models of baseline and four scenarios using the material flow and waste stream data of Taiwan with reference to a classification of four kinds of circular intervention from a review paper. We provide the details about the modeling results and settings for diverting plastic to the solid recovered fuel for power generation, closing the loops of plastic bags, extending the life of plastic cabinets and other plastic products, and improving the plastic products supply chain’s resource efficiencies. In the illustration of the results of GHG reductions in the supply chains and waste treatment activities, we present Sankey diagrams, which make the analysis of supply chains more straightforward. The developed method to render the Sankey diagram from the modeling result of an input–output-based model is presented in this article.