Closing carbon cycles: Evaluating the performance of multi-product CO₂ utilisation and storage configurations in a refinery

Carbon capture and utilisation (CCU) has the potential to provide business cases as CO₂ waste streams are turned into feedstock for the synthesis of marketable products. Although CCU could reduce fossil resource demand, its capability as a climate change mitigation option is under debate. In contrast to single-product CCU, this prospective study explores the techno-economic and environmental feasibility of novel systems that include more than one CO₂ utilisation product. The combination of multi-product CCU with CO₂ storage is also investigated. Two configurations have been designed, in which CO₂ is captured in a refinery and converted into dimethyl ether (DME) and polyols, simultaneously (parallel configuration) or in two consecutive cycles (cascade configuration). Compared to a reference system without capture, results show that the largest direct CO₂ emission reductions are achieved with CCS without utilisation (−70%) but at the expenses of higher total costs (+7%). Multi-product CCU systems show lower fossil depletion and costs than the reference without capture (−10% and −9%, respectively) because of feedstock replacement by the CO₂ utilised. Combination of multi-product CCU with storage turns to be the best alternative for reduced climate change potential (−18% relative to the reference) while still been economically feasible. In addition to lower upstream emissions due to fossil feedstock replacement by utilising CO₂, process direct emissions diminish owing to storage. No significant differences were found between the cascade and the parallel configurations. The extra effort to recycle CO₂ in the cascade configurations is neither penalised nor rewarded.