Integration of adsorption-based carbon capture with alkaline wastewater neutralization: Pilot-scale techno-economic and environmental assessment

Abstract

The integration of carbon capture and utilization (CCU) technologies into industrial processes opens new pathways to mitigate climate change while aligning with the principles of the circular economy. This study evaluates the technical, environmental and economic performance of using CO2 captured via vacuum swing adsorption (VSA) for the on-site neutralization of alkaline wastewater generated in a food processing facility. The pilot-scale VSA unit of this study treated flue gas from a natural gas-fired boiler, producing 79 tons of CO2 per year with 76% (w/w) of CO2 purity, 67% of CO2 recovery and specific energy demand of 0.61 kWh/kgCO2, including energy for final CO2 compression. The captured CO2 was successfully used to neutralize the alkaline wastewater. A life cycle assessment (LCA) was carried out to compare three neutralization scenarios: (i) conventional treatment with sulfuric acid (H2SO4), (ii) the use of commercial CO2, and (iii) a circular scenario with the on-site reuse of the CO2 captured through VSA. The LCA results indicate that the circular scenario reduces the climate change impact by 65% and 48% compared to the commercial CO2 and H2SO4 scenarios, respectively. The environmental impact in the circular scenario is at least 78% lower than the worst-case scenario across nearly all impact categories. From an economic perspective, the circular scenario achieved similar costs to using H2SO4 while offering a 40% cost reduction compared to commercial CO2. These findings demonstrate that on-site CCU for alkaline wastewater treatment is technically feasible at pilot scale and a more sustainable alternative.