Acid-regulated ensiling as an efficient pretreatment mitigates antibiotic resistance and enhances methanogenesis from...

EFR poses severe environmental and public health risks due to residual antibiotics and enriched ARGs. Traditional treatments are hindered by high costs, limited detoxification efficacy, and resource waste, heavily restricting EFR valorization. This study developed a sequential ensiling and AD process, regulated by a formic acid, to achieve pollutant elimination and bioenergy recovery. The results showed that during the 56-day ensiling stage, the addition of 2 mL/kg formic acid facilitated rapid acidification and shifted the dominant microbial community to Lactobacillaceae, significantly reducing the absolute abundances of specific ARGs and MGEs, including ermF, ereA, mphA, and IS613. Other ARGs and MGEs experienced a transient increase at day 7 but declined to their initial levels by day 56. Conversely, a high formic acid dosage of 4 mL/kg caused severe abiotic inhibition, which hindered microbial succession and maintained a bacterial community composition similar to the raw material, while successfully preserving 72% of WSC and 95% of dry matter. In the subsequent AD stage, all ensiled substrates achieved COD removal efficiencies exceeding 54%. The cumulative methane yields of the ensiled groups increased compared to the unensiled control, with the high-dose and low-dose treatments achieving increases of 9.9% and 3.6%, respectively. Although the vast background ARGs concentration in the inoculum sludge influenced the final digestate, ARGs and MGEs were not further enriched following AD. These findings indicate that pretreatment with 2 mL/kg formic acid optimally balances ARGs elimination with energy recovery. Ultimately, this study provides a highly cost-effective technical framework for EFR valorization and offers profound mechanistic insights into microbial community-driven ARGs suppression via niche preemption.