System-level benefits of extracting and treating saline water from geologic formations during national-scale carbon capture and storage

Despite economic, political, legal, and technical challenges, carbon dioxide (CO2) capture and storage (CCS) holds promise as a means to substantially reduce anthropogenic atmospheric emissions of carbon dioxide. One of the technical challenges to CCS is an accurate quantification of the potential geologic storage resource. This analysis uses the publically available national-scale, systems-level Water Energy and Carbon Sequestration simulation model (WECSsim©), to show that, depending on assumed boundary conditions, the majority of storage associated with large-scale CCS in the U.S. (on the order of 90-100 GT of total reduced emissions) would occur at a small number of well-located sites with favorable geologic properties. WECSsim, through the use of marginal abatement cost curves, shows that under such a scenario, added costs associated with resident saline water extraction, transport, and treatment (SWETT) are justified by resulting increases in carbon dioxide storage efficiency in the geologic formation. This argument is strengthened when geologic uncertainty is taken into consideration. Like an insurance policy, the enhanced carbon dioxide storage efficiency that comes from SWETT adds well-defined costs to reduce potential economic risks associated with overestimates of the available geologic storage resource.