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

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.