Life Cycle Assessment and Social Benefits of Producing Bioplastic Polyhydroxyalkanoates (PHAs) via Integrating Electrochemical CO₂Conversion and Microbial Fermentation

Integrating the carbon dioxide reduction reaction (CO₂RR) with fermentation to produce polyhydroxyalkanoates (PHAs) offers a novel and cutting-edge approach to synthesizing bioplastics compared with other state-of-the-art technologies, such as fossil fuel-based plastics and other renewable-sourced plastic production routes. However, the sustainability of this type of integrated chemical and biological process has not been quantitatively assessed, and the environmental impacts and potential social benefits have not been analyzed. In this study, rigorous life cycle analyses and a comprehensive environmental impact analysis were performed to evaluate CO₂RR-based PHA products, encompassing both raw material sources and polymer production. Sensitivity and scenario analyses were conducted to evaluate its potential for sustainability, including the social benefits associated with end-of-life management. In the base scenario using the US electricity mix without byproduct displacement, the system resulted in net emissions of 176.3 kg of CO₂e per kg of PHA, which establishes the baseline for comparison. The results show that, compared to fossil fuel-based plastics, CO₂RR-based PHA has the potential to reduce carbon emissions by up to 80.34 kg of CO₂e/kg of PHA when utilizing renewable energy and byproducts. The identified factors, such as PHA yield, the intermediate (C2+) production rate, and nutrient utilization, are key parameters responsible for up to 108% of the variance in greenhouse gas (GHG) emissions and other environmental performance. Considering the conversion and end-of-life management, CO₂RR-based PHA has the potential to reduce up to 84.84 kg CO₂e/kg PHA. In terms of social benefits, this process can avoid total social damage costs of about $1.45 trillion, which is nearly twice the global plastic industry market value. However, under less favorable conditions, the process could increase emissions, resulting in an additional $69 billion in social damage. Overall, the findings suggest that converting CO₂ to PHA via an electro-biointegrated pathway offers a promising pathway to reduce GHG emissions and associated environmental and social impacts compared to fossil-based and other renewable plastics.