Costs to achieve target net emissions reductions in the US electric sector using direct air capture

Abstract

This paper examines the scale and costs of using direct air capture (DAC) with CO2 storage to reduce net CO2 emissions from the US electric sector by 70% in 2050 relative to 2010. Least-cost emission and technology trajectories are generated using an optimization-based stock-and-flow model of electricity generation to meet the 70% target. The analysis finds that the 30%–44% reduction in emissions projected under a least cost business-as-usual (BAU) scenario dominated by natural gas would fall well short of the 70% reduction target at 2050. Delaying reductions in BAU emissions beyond 2030 would require deployment of DAC to achieve the 70% target. Further delays to reduce BAU emissions until 2035 would require up to 1.4 Gt CO2 of DAC capacity to achieve the 70% target. Delaying reductions in BAU emissions beyond 2035 would require so much DAC deployment as to be implausible, placing the 70% target out of reach for most scenarios. Each year of delay in reducing CO2 emissions beyond BAU after 2020 increases costs to achieve the 70% target. A DAC-based emissions reduction future could cost an additional 580–2015 billion USD through 2050 compared to emissions mitigation starting immediately. This translates to approximately 100–345 million USD per day of delay starting in 2020. These costs arise not just from building DAC plants, but from replacing relatively young fossil fuel plants being built today with renewables as well as for the electric power needed for DAC. These results make clear that minimizing the costs of DAC deployment depend on reducing BAU emissions as early as possible, and if done quickly enough, DAC can be avoided altogether—which reduces costs the most. Hence there should be no delay in aggressively reducing emissions from the US electric sector.