Life cycle assessment of polyols for polyurethane production using CO2 as feedstock: insights from an industrial case study

Abstract

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.