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 (CO _2 ) in the atmosphere, direct air CO _2 capture (DACC) technologies must (a) satisfy the process requirements for heat and electricity with energy that has few if any CO _2 emissions, and (b) physically isolate the CO _2 from the atmosphere after its extraction from the air. To isolate the CO _2 from the atmosphere at meaningful scale, the CO _2 will likely need to be geologically stored in deep saline aquifers. Here we propose to leverage geologic CO _2 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 CO _2 -driven geothermal utilization (SB-CO _2 DGU, also known as CO _2 Plume Geothermal) circulates some of the emplaced CO _2 to extract geothermal heat in a closed loop between the subsurface reservoir and surface geothermal facility. The proposed integration of DACC and CO _2 -driven geothermal Utilization and Storage (DACCUS) adds CO _2 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 CO _2 from large point sources, and then integrates CO _2 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 CO _2 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.

Keywords

• direct air CO2 capture
• geothermal energy
• CO2 capture
• utilization
• storage
• negative emissions