Mechanisms of biochar-mediated reduction of antibiotic-resistant bacteria and biogas production enhancement in anaerobic digesters

This study examined the impact of different biochar (BC) as an anaerobic digestion (AD) additive on antibiotic-resistant bacteria (ARB) survival and AD performance using dairy cow manure. Bamboo BC and Olive BC with different particle sizes were added into the mesophilic AD at 15 g/L and 30 g/L dosages (Bamboo-15, Bamboo-30, Olive-15, and Olive-30). The study provides a detailed analysis of biogas production, organic metabolism, and ARB and microbial dynamics, elucidating the mechanisms by which BC influences AD. Findings reveal significant reductions in CEZ-resistant bacteria (CEZ-r) across all reactors, ranging from 12.88 % to 76.47 %. Both Bamboo and Olive BC increased CEZ-r removal by 3.08–5.94 times compared to the control. Additionally, BC supplementation prevented the rise in CEZ-r percentage within the total bacteria count observed in the control reactor. Bamboo BC outperformed Olive BC in enhancing biogas yield, with Bamboo-15 and Bamboo-30 showing significant increases of 43.2 % and 48.0 %, respectively, compared to the control. Adding BC in AD regulates ARB by decreasing potential ARG hosts and impeding the transmission of resistance. It also enhances biogas production by improving the efficiency of methanogenic bacteria and optimizing the methanogenic pathway. This research provides insights into how BC can be used to enhance AD performance and mitigate ARB proliferation, offering a sustainable approach to waste management and energy production.