Linking the deployment of carbon dioxide removal to emissions from hard to abate sectors

In this study we used the Global Change Analysis Model (GCAM) to analyze how existing mitigation levers impact the deployment of carbon dioxide removal (CDR) technologies when the demand for CDR is linked to emissions from sectors with higher marginal abatement costs. We compare an array of scenarios with differing assumptions regarding total energy demand and availability of renewable resources. We find that CDR is necessary to reach mid-century net-zero emissions goals even in scenarios with low energy demand and readily available renewable energy, as sectors with higher marginal abatement costs have trouble decarbonizing even late in the century. In all scenarios, emissions from the electricity sector have a net zero target of 2040 for OECD countries and 2060 for non-OECD countries. The portfolio of CDR technologies available for deployment is also broader than those normally accounted for in GCAM, we include Direct Air Capture (DAC), Oceanic Enhanced Weathering (OEW), and Terrestrial Enhanced Weathering (TEW), as criticisms regarding more popularly modelled CDR technologies such bioenergy carbon capture and sequestration (BECCS) have drawn attention to these less widely acknowledged technologies (1). We keep demand for these technologies linked to CO emissions not originating from the electricity sector, while manipulating energy demand and supply. Figure 1 shows a scenario matrix wherein these demand and supply side levers are being manipulated. On the supply side, there are the default renewable scenarios and advanced renewable scenarios, where we assume that renewable energy becomes more widely available earlier in the century. On the demand side, we utilize assumptions from the shared socioeconomic pathways (SSPs), using SSP5 as a basis for a high energy demand future, SSP2 as a basis for a middle of the road energy demand future, and SSP1 as a basis for a low energy demand future, following the assumptions made by Grubler et al. (2).