Environmental potential of carbon dioxide utilization in the polyurethane supply chain

Abstract

Potential environmental benefits have been identified for the utilization of carbon dioxide (CO₂) as a feedstock for polyurethanes (PUR). CO₂ can be utilized in the PUR supply chain in a wide variety of ways ranging from direct CO₂ utilization for polyols as a PUR precursor, to indirect CO₂ utilization for basic chemicals in the PUR supply chain. In this paper, we present a systematic exploration and environmental evaluation of all direct and indirect CO₂ utilization options for flexible and rigid PUR foams. The analysis is based on an LCA-based PUR supply chain optimization model using linear programming to identify PUR production with minimal environmental impacts. The direct utilization of CO₂ for polyols allows for large specific impact reductions of up to 4 kg CO₂-eq. and 2 kg oil-eq. per kg CO₂ utilized, but the amounts of CO₂ that can be utilized are limited to 0.30 kg CO₂ per kg PUR. The amount of CO₂ utilized can be increased to up to 1.7 kg CO₂ per kg PUR by indirect CO₂ utilization in the PUR supply chain. Indirect CO₂ utilization requires hydrogen (H₂). The environmental impacts of H₂ production strongly affect the impact of indirect CO₂ utilization in PUR. To achieve optimal environmental performance under the current fossil-based H₂ generation, PUR production can only utilize much less CO₂ than theoretically possible. Thus, utilizing as much CO₂ in the PUR supply chain as possible is not always environmentally optimal. Clean H₂ production is required to exploit the full CO₂ utilization potential for environmental impact reduction in PUR production.