A potential for climate benign direct air CO2 capture with CO2-driven geothermal utilization and storage (DACCUS)

Abstract

Abstract To reduce the overaccumulation of carbon dioxide (CO2) in the atmosphere, direct air CO2 capture (DACC) technologies must (a) satisfy the process requirements for heat and electricity with energy that has few if any CO2 emissions, and (b) physically isolate the CO2 from the atmosphere after its extraction from the air. To isolate the CO2 from the atmosphere at meaningful scale, the CO2 will likely need to be geologically stored in deep saline aquifers. Here we propose to leverage geologic CO2 storage (GCS) in sedimentary basin geothermal resources to produce geothermal heat and electricity for the process energy requirements of solid sorbent DACC. This sedimentary basin CO2-driven geothermal utilization (SB-CO2DGU, also known as CO2 Plume Geothermal) circulates some of the emplaced CO2 to extract geothermal heat in a closed loop between the subsurface reservoir and surface geothermal facility. The proposed integration of DACC and CO2-driven geothermal Utilization and Storage (DACCUS) adds CO2 from the air to this closed loop system that produces renewable energy for use in the DACC process. The strategy first primes the GCS reservoir with CO2 from large point sources, and then integrates CO2 from DACC facility to form the DACCUS system. We focus on the process integration of DACCUS and present a case study of its potential deployment and scaling in the Gulf Coast of the United States. We combine data from prior analyses for a novel investigation of two DACCUS configurations: (1) a DACCUS heat system uses the geothermal heat to regenerate the solid sorbent in the DACC process, and (2) a DACCUS heat and power system uses the electricity generated from the produced geothermal heat for the DACC process. In general, deeper CO2 storage reservoirs (>3.5 km) with higher geothermal temperature gradients (>35 °C km−1), may provide sufficient production wellhead temperatures (>100 °C), and satisfy the electric load in 93% of the combinations of reservoir characteristics we examined.