(718a) Hybridization Potential of Carbon Capture and Utilization: A Smoother Transition Towards a Decarbonized Ethylene Production.

Meeting the Paris Agreement will require global climate change mitigation efforts, among which carbon capture and utilization (CCU) emerges as an appealing strategy as it can bring value to industrial activities while utilizing captured CO₂. With this spirit, at present, direct electro- and thermo- catalytic routes are being investigated extensively to produce a myriad of valuable CO₂-based chemicals. The main difference between these routes is that the former activates the CO₂ molecule directly with electricity, whereas the latter is based on the hydrogenation of CO₂ in tandem with electrocatalytic water splitting.

So far, however, these two leading CCU technologies, electro- and thermo- catalytic routes, have been mostly assessed as stand-alone systems. In addition, even though significant high costs characterize both routes compared to the fossil-based alternative, the hybridization potential of fossil and CCU technologies, from a process perspective, remains mostly unexplored. Hence, a comparative analysis of these routes and their hybridization is considered critical for establishing future research directions and developing effective environmental regulations.

In our work, we focus on ethylene, an important building block of the chemical industry, and cover this research gap considering various power (i.e., wind, solar, and nuclear) and CO₂ sources (i.e., capture from natural gas or coal power plants, or directly from the air). Our results show that CCU can help to significantly reduce the carbon footprint of ethylene and the impacts on human health, ecosystem quality, and resource depletion can be significantly reduced. The thermo-route is currently economically and environmentally superior when compared to the electro-route, yet the latter shows the highest potential for improvements, being at an earlier stage of development with respect to the thermo-route. The substantial energy needs, for both routes, make the production of CO₂-based ethylene, at present, economically unappealing, i.e., a 1.7 to 3.9-fold decrease in costs would be required to become competitive with the fossil-based alternative. In order to overcome this barrier, we apply optimization tools and the concept of hybridization to smooth the transition towards more sustainable chemicals. In particular, we developed a Linear Programming (LP) model considering the whole range of power and CO₂ sources to quantify the optimal hybrid for different decarbonization levels. Accordingly, we find that it is possible to produce cradle-to-gate carbon-neutral ethylene with only a 1.3-fold increase in cost by optimally combining fossil and CCU routes.