Carbon Negative Geothermal: Financial Analysis for Combined Geothermal, Bioenergy and Carbon Dioxide Removal

Abstract

Coupling bioenergy with carbon capture and storage (BECCS) is a net carbon negative process that has been highlighted by the Intergovernmental Panel on Climate Change as an important technology for offsetting greenhouse gas emissions. Despite their proposed efficacy as both a power production and negative emissions tool, BECCS technologies currently lack widespread use due totheir high costs. Coupling geothermal fields with BECCS operations by dissolving biogenic CO2 in geothermal brine could reduce the transportation and injection costs by leveraging geothermal reinjection apparatus for sequestration.
Dissolved biogenic CO2 could be stored more safely in a geothermal reservoir through pressure maintenance, sidestepping leakage concerns from storing buoyant supercritical CO2. Additionally, geothermal and bioenergy synergize as electricity generation technologies, leading to higher utilization efficiencies.
Our analysis shows that geothermal-BECCS plants could have operational emissions intensities of -137 gCO2/kWh to -928 gCO2/kWh, offsetting 30% to 206% of the emissions from a standard natural gas plant. For the CO2 price of NZD 80/tonne in 2022, geothermal-BECCS could have a levelized cost of electricity (LCOE) of NZD 163 to 203/MWh, cheaper than overseas standalone BECCS estimates NZD 267 to 426/tonne. For a projected CO2 price increase of NZD 160/tonne by 2035 suggested by the Climate Change Commission, geothermal-BECCS plants could have LCOEs as low as NZD 29 to 54/MWh. This would be more competitive than geothermal plants while also removing up to 110,000 tonnes of CO2 a year.