Life cycle assessment of polyols for polyurethane production using CO2 as feedstock: insights from an industrial case study†
Polyethercarbonate polyols from carbon dioxide (CO2) are starting to be synthesized on industrial scale. These polyols can be further processed into polyurethanes enabling CO2 to be utilized in large amounts. Utilization of CO2 as alternative carbon feedstock for polyols is motivated from the potential to reduce greenhouse gas (GHG) emissions and fossil resource depletion. This article presents a life cycle assessment for production of CO2-based polyethercarbonate polyols in a real industrial pilot plant. The considered cradle-to-gate system boundaries include polyol production and all upstream processes such as provision of energy and feedstocks. In particular, provision of CO2 from a lignite power plant equipped with a pilot plant for CO2 capture is considered. Production of polyols with 20 wt% CO2 in the polymer chains causes GHG emissions of 2.65–2.86 kg CO2-eq kg−1 and thus, does not act as GHG sink. However, compared to production of conventional polyether polyols, production of polyols with 20 wt% CO2 allows for GHG reductions of 11–19%. Relating GHG emission reductions to the amount of CO2 incorporated, up to three kg CO2-eq emissions can be avoided per kg CO2 utilized. The use of fossil resources can be reduced by 13–16%. The impacts reductions increase with further increasing the CO2 content in the polyols. All other investigated environmental impacts such as eutrophication, ionizing radiation, ozone depletion, particulate matter formation, photochemical oxidant formation, and terrestrial acidification are also lowered. Therefore, synthesis of polyethercarbonate polyols from CO2 is clearly favorable compared to conventional polyether polyols from an environmental point of view.