Biochar has been reported as an effective additive to improve methane production during anaerobic digestion (AD). However, the mechanism for such a stimulatory impact remains unclear. Here we investigated the capability of three pyrolytic biochars with distinctive electrochemical properties (BC300, BC500, BC700) to promote methanogenic performance of anaerobic digesters treating waste activated sludge (WAS). The cumulative methane production and the maximum methane production rate were increased by 46.9% and 181.6%, respectively, with BC300 amendment. By characterizing the electrochemical properties of biochar, we found out that methane production in AD of sludge was positively correlated to biochar’s electron-donating capacity (EDC) rather than its bulk electrical conductivity. These results indicate that the electron transfer mediated by the redox-active functional groups may prevail over the direct electron migration as the predominant mechanism to facilitate interspecies electron transfer in syntrophic communities for enhanced methanogenesis. Microbial community analysis suggests that biochar enriched Methanosarcina and Methanobacterium. Overall, this study shows that functional groups-mediated electron transfer contributes greatly to the improved methane production in WAS digester with biochar amendment.

据报道，生物炭是在厌氧消化（AD）期间提高甲烷产量的有效添加剂。但是，这种刺激作用的机制仍不清楚。在这里，我们研究了三种具有独特电化学特性的热解生物炭（BC300，BC500，BC700）促进厌氧消化池处理废活性污泥（WAS）的产甲烷性能的能力。BC300修正案后，累计甲烷产量和最高甲烷生产率分别提高了46.9％和181.6％。通过表征生物炭的电化学特性，我们发现污泥AD中甲烷的产生与生物炭的电子给体容量（EDC）呈正相关，而不是其整体电导率。这些结果表明，由氧化还原活性官能团介导的电子转移可能胜于直接电子迁移，这是促进在营养界的种间电子转移以增强产甲烷作用的主要机制。微生物群落分析表明生物炭富集甲烷藻和甲烷杆菌。总的来说，这项研究表明，官能团介导的电子转移极大地促进了生物炭改良剂对WAS消化池中甲烷产量的改善。