Carbon Dioxide Sequestration and Carbon Crediting Using CO ₂ -Neutralized Alkaline Wastewaters

Industrial alkaline wastewaters (AWW) require neutralization prior to discharge into rivers to meet environmental and regulatory constraints. Conventional approaches use strong mineral acids, which pose corrosion risks and fully neglect the potential for urgently needed carbon sequestration. Neutralizing AWW with CO2 preserves and exploits existing alkalinity to permanently sequester CO2 as bicarbonate within the riverine and ultimately the ocean’s dissolved inorganic carbon (DIC) pool. We introduce and implement Wastewater Alkalinity Preservation (WAP): a process that converts hydroxide alkalinity into carbonate alkalinity without decreasing Total Alkalinity, enabling persistent (>1,000 years) carbon sequestration and direct, on-site monitoring, reporting, and verification (MRV) for carbon crediting. A global sensitivity analysis across river systems supports high and sustainable carbon retention. A robust, bottom-up analysis indicates a current global potential of 11–32 Mt CO2 per year at present AWW volumes. In support of Carbon Dioxide Removal (CDR) eligibility and crediting across global river systems, the proposed process control ensures accounting via pCO2 matching of incoming and discharged waters, minimizes losses, and provides redundant consumption metrics to establish effectivity. A CO2 sequestration potential of WAP of several hundred Mt CO2 per year can be projected until 2100 depending on economic growth, underlining the capacity of WAP as a powerful climate change mitigation measure.