Combining enhanced basalt weathering with soda saline soil: A novel CO₂ mineralisation strategy

Enhanced rock weathering in saline–alkaline soils can couple CO₂ mineralisation with reclamation of salt-affected land. We incubated 30 g basalt with 30 g sodic saline soil for 90 days at 15 °C using three particle sizes (0.074, 0.42 and 5 mm) and two water additions (30 and 60 g). Endpoint aqueous chemistry, SEM–EDS, thermogravimetric analysis and PHREEQC saturation modelling were integrated with a regional life-cycle assessment for Jilin Province, China. Endpoint Ca accounting yielded apparent weathered-basalt masses, which were converted using a primary Ca-only carbonate capacity of 0.072 g CO₂ g⁻¹ basalt and an all-base-cation carbonate-equivalent upper capacity of 0.142 g CO₂ g⁻¹ basalt. Particle-size-specific effective rates linked the incubation results to 30-year weathering trajectories. Gross CDR reached 72.45–72.47 kg CO₂ t⁻¹ basalt in the primary case and 141.92–141.96 kg CO₂ t⁻¹ basalt in the upper case. Across twelve scenarios, primary-case net CDR ranged from −5.53 to 38.45 kg CO₂-eq t⁻¹ basalt, while upper-case net CDR ranged from 63.96 to 107.92 kg CO₂-eq t⁻¹ basalt. Net-removal costs ranged from USD 1327–29,328 t⁻¹ CO₂ in the primary net-removing scenarios and from USD 473–4667 t⁻¹ CO₂ in the upper case. The identified 6376,490 ha of Jilin cropland, equivalent to 482.06 Mt basalt at 75.6 t ha⁻¹ , had gross capacities of 34.93 Mt CO₂ (primary) and 68.43 Mt CO₂ (upper). Finer particles reached the composition-controlled capacity sooner, whereas coarse basalt had lower supply-chain emissions in the evaluated scenarios.