Carbon-dependent net-zero emission energy systems without reliance on fossil fuels and bioenergy

Abstract Existing climate change mitigation scenarios for attaining the 1.5°C goal generally phase out hydrocarbon use through decarbonization of the energy system to eliminate fossil fuel usage. However, they require rapid changes in energy-demand technologies and human behaviors or extensive reliance on bioenergy for carbon dioxide removal (CDR). Carbon capture and utilization (CCU) presumably could support to alter such energy systems, considering recent technological advancements in direct air capture (DAC) and renewable-based hydrogen. Here, we developed a CCU-based scenario under the 1.5°C climate goal using a global energy system model. In the scenario where CCU is mainly introduced by limiting demand-side electrification, bioenergy, and CDR, CCU-based synthetic fuel reaches 30% of global energy demand to achieve net-zero emissions by 2050. In contrast to existing 1.5°C scenarios, this CCU scenario is characterized by greater availability of hydrocarbons in energy demand, reaching 280 EJ in 2050, whereas fossil fuel and bioenergy supplies decrease to 60 EJ and 100 EJ, respectively. Despite moderate demand-side electrification, this scenario involves rapid upscaling of renewable energy and DAC, which reach 600 EJ and 10 Gt-CO2 per year by 2050, respectively. While the CCU-based scenario involves multiple challenges on energy supply transformation and associated energy investments, it provides an alternative mitigation option that considers the difficulties in rapid demand-side changes and the risks of bioenergy and CDR.