Carbon capture via accelerated weathering of limestone: Modeling local impacts on the carbonate chemistry of the southern North Sea

Abstract

Human activities are responsible for a > 45 % rise of atmospheric CO2 since the industrial revolution started; burning of fossil fuels being the largest source. Via accelerated weathering of limestone (AWL), CO2 can be captured from effluent gas streams and stored in the marine environment primarily in the form of bicarbonate. We studied the CO2 storage capacity and how AWL-derived water impacts the carbonate chemistry of the southern North Sea. Therefor, a three-dimensional hydrodynamic model was coupled with a sub-module to model the carbonate chemistry. We studied three scenarios: 1) scrubbing effluent gas streams of a combined heat and power plant (60 kW), 2) scrubbing 10 % or 3) 100 % of the flue gas of a coal-fired power plant (750 MW). Whereas, impacts on seawater carbonate chemistry due to AWL discharge were imperceptible in the first scenario, a maximum change in pHT and calcite saturation state of 0.1 and 0.6 was found in scenario 2. In scenario 3, the decrease in pHT exceeded 1 around the discharge site and the calcite saturation state reached 8 in large parts of the Jade Bay, posing the possibility of significant impacts on the marine ecosystem. Abiotic precipitation of calcite might occur around the discharge site. In all three scenarios, 50 % of the captured CO2 re-entered the atmosphere after the simulated time period of one year. This study shows that care is needed in siting, sizing and operating AWL facilities to maximize climate and ocean ecosystem benefits while minimizing negative environmental impacts.