Accounting for carbon flows into and from (bio)plastic in a national climate inventory

Abstract

Despite the time-dependent behavior of carbon stored in plastic materials, literature assessing carbon flows into and from plastic typically applies a static approach. To better understand the climate impacts of such storage, this study explores how carbon stored in plastics can contribute over time to the national climate inventory with various emphasis on recycling. This is accomplished by implementing material stock change estimations for carbon in plastic materials that follow first-order decay and include impacts from recycling rates in the Integrated MARKAL-EFOM System model generator for Sweden (TIMES-Sweden). Thereafter, three approaches to how carbon released from the plastic material stock is accounted for in the national climate inventory were applied to determine how each approach affects resulting emission and net-zero pathways in different recycling rate scenarios. An accounting approach that follows the first-order decay pattern of material stocks was found to be important for capturing the impacts of recycling and for neither over- nor underestimating the emission impact from carbon stored in plastics. Accounting for carbon stored in plastics may provide important incentives for producing renewable plastics and reducing dependence on carbon removal technologies. Because of its synergies with recycling, the carbon storage potential of plastic products is well worth recognizing and promoting in a policy setting that aims for circularity. For Sweden, this reduces the need for bioenergy carbon capture and storage and makes more biomass-based carbon and electricity available for use elsewhere in the energy system.