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/kg_CO2, 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.