Towards sustainable elastomers from CO2: life cycle assessment of carbon capture and utilization for rubbers

Abstract

Elastomers have been recently proposed to integrate CO₂ as carbon feedstock. These elastomers are produced by reacting carbon dioxide with propylene oxide and maleic anhydride. The resulting cross-linkable polyether carbonate polyols can be combined with isocyanates to form a novel class of polymers: CO₂-based rubbers. These CO₂-based rubbers are able to substitute conventional rubbers in synthetic elastomer products, such as sealants or flexible tubes. In this work, we present the first Life Cycle Assessment for CO₂-based rubbers. To compare CO₂-based and conventional rubbers our assessment considers all relevant life cycle stages from cradle-to-grave. The production system of CO₂-based rubbers encompasses a nearby ammonia plant as a CO₂ source, the conversion of CO₂ to polyols, the reaction of polyols with isocyanates and finally, the incineration of CO₂-based rubbers. Our analysis shows that CO₂-based rubbers containing approx. 20% wt. CO₂ have a global warming impact of 4.93 kg CO₂-eq. Thus, CO₂-based rubbers are no carbon sink. However, CO₂-based rubbers reduce global warming impact by up to 34% if they substitute, for example, hydrogenated nitrile butadiene rubber on an equal mass basis. Fossil resource depletion is reduced by up to 33%. In contrast, other impact categories like ionizing radiation are increased by the utilization of CO₂-based rubbers in some cases. Thus, our study indicates that CO₂-based rubbers provide a promising pathway to reduce global warming impact and fossil resource depletion. However, it is likely that some other environmental impact categories such as ionizing radiation and freshwater eutrophication are increased.