Can CO₂ and Renewable Carbon Be Primary Resources for Sustainable Fuels and Chemicals?

Abstract

RecommendationsW ith the increasing global population, the demands for fuels and chemicals are greater than ever.Greenhouse gas (GHG) emissions from the use of fossil fuel-based conventional feedstocks are also a matter of great concern.A revolution is needed to replace the conventional feedstocks, processes, and the materials that enable these processes with more sustainable alternatives such as renewable biomass, recycled carbon, and carbon dioxide (CO 2 ).In fact, we are at the verge of witnessing a shift from conventional fossil fuelbased petrochemical conversion to more sustainable processes that utilize unconventional feedstocks.Specifically, CO 2 can be viewed as a renewable source of carbon, which can be used as a C1 building block to valuable chemicals.Replacing petrochemical-based hydrocarbons would require massive sourcing of renewable hydrogen and carbon.Advances are underway in producing so-called "green" hydrogen, as the costs of renewable energy has significantly reduced in recent times.However, major renewable energy sources, such as solar and wind, are distributed with intermittent supply and spatiotemporal variability and uncertainty.Natural gas-based hydrogen generation is mature, but we must remove CO 2 to make it sustainable.Significant scientific and research challenges need to be resolved in the areas of hydrogen generation, separation, storage, and utilization to envision a sustainable future hydrogen economy.On the other hand, CO 2 capture and utilization/storage (CCUS) not only shows great promise for decarbonizing the hydrogen, energy and manufacturing sectors, it allows one to tap into large volumes of CO 2 that are available from stationary/point sources (e.g., fossil power plants, cement, iron and steel, agricultural processing, etc.) and from air via direct air capture.CO 2 capture remains expensive, and the associated parasitic energy penalty remains high.CO 2 is a stable gas that is mostly available as a combustion product after we burn fossil fuels.The energetics of CO 2 utilization is a key challenge.We need novel materials, methods, and multiscale approaches before we envision large-scale implementation of CO 2 as a primary resource for fuels and chemicals.Biomass and recycled plastics can constitute a major portion of a future feedstock portfolio for both hydrogen and carbon toward meeting our increasing demands for hydrocarbons.To that end, the concepts of integrated biorefineries and circular economy require further work in terms of resource utilization, materials development, and process intensification, among others.To overcome the intrinsic thermodynamic stability of CO 2 , a large amount of chemical energy is required.Thermocatalytic CO 2 conversion is a known pathway for CO 2 upgrading and,

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