Using desulfurization wastewater to mitigate lime disinfectant inhibition and enhance anaerobic digestion of swine manure.

Biogas production from swine manure is hindered by excessive Ca2+ introduced through lime disinfectants, causing microbial inhibition and process instability. Meanwhile, NaOH-based alkaline solutions widely applied for biogas purification generate desulfurization wastewater enriched with carbonate ions. Leveraging this connection, this study proposes an integrated strategy that couples NaOH-based biogas upgrading with mitigation of lime-induced inhibition. CO2 removal via NaOH bubbling increased CH4 purity to 83.1 % at 80 g/L NaOH. The resulting desulfurization wastewater was subsequently reused as an alkaline additive for anaerobic digestion of lime-contaminated manure. This approach increased cumulative biogas yield by 4.8-fold, reduced Ca2+ from 7.8 to 2.1 g/L, and lowered volatile fatty acids by nearly 80 %. SEM-EDS and XRD confirmed the formation of CaCO3 and Ca5(PO4)3OH, enabling simultaneous calcium removal and phosphorus recovery. Enhanced acetate-driven methanogenesis aligned with the rise in biomethane. Overall, this carbon-alkali synergistic strategy stabilizes anaerobic digestion, promotes desulfurization wastewater utilization, and improves renewable energy generation.