Selection cannot be made solely using MIs and value. System-level properties of the material and product must be considered, such as feedstock renewability, end-of-life management, product recyclability, and circularity . To fit into a circular economy framework, a renewable feedstock is one in which the carbon has been recirculated, including carbon obtained from biomass, industrial by-products, waste CO2, or recycled plastics. While all of the plastics discussed can be made in whole or in part from bio-based feedstocks, several are disproportionately petroleum-derived (PS foam, virgin PET, PP) . The social costs of petroleum-derived feedstocks extend beyond CO2 emissions, water usage, and environmental persistence discussed above . For example, human and ecosystem health impacts from oil spills , and methane venting by the oil and gas industry pose substantial social costs that are not considered in the current framework (Figure ) . Meanwhile, the sustainability of PLA, CDA, and paper feedstocks depends on agricultural practices, which can vary considerably . CDA has historically been a mixed feedstock wherein the cellulose was bio-derived, and the carbon within the acetyl modification was derived from coal. Recognizing the non-renewability of coal as a carbon source for the acetyl functionality, more sustainable grades of CDA are being produced in which the acetyl carbon is derived from molecularly recycled mixed waste that would otherwise be landfilled. Today, the vast majority of managed plastic waste is landfilled , some is incinerated, and even less is recycled and composted . For example, municipal mechanical recycling facilities currently do not accept foams , resulting in their disposal in landfills or by incineration. Landfills contribute ~10% of global methane emissions, and their leachates can diminish fresh and groundwater resources . Although incineration of waste can reclaim embedded energy, the process releases GHGs and reduces air quality. The social costs of methane emissions and air pollution were estimated to be $3.5 per kg CH4 (~16 times that of CO2) and to range from $100-172 per kg particulate matter with a diameter less than 2.5 µm (PM2.5) (~450-782 times that of CO2), respectively . While direct exchange constants for the social costs of landfilling and waste incineration are challenging due to their dependencies on geographic location and facility specifications , these figures for methane and PM2.5 emissions illustrate the magnitude of their costs to society and in turn, the potential costs of these waste management strategies.