Comparative Analysis of the Biochar Derived from Antibiotic Fermentation Residue and Corn Straw and its Role in Promoting Anaerobic Digestion: a Characterization of the Biochar, Microbial Community, and Metabolic Pathways

The employment of biochars was an effective strategy for addressing the challenges associated with inadequate gas production, acid inhibition, and system instability associated with the anaerobic digestion (AD) of food waste. The resource-based and harmless disposal of antibiotic fermentation residue was a matter of great urgency, and presented a good opportunity for the preparation of biochars. The effects of biochars derived from spectinomycin fermentation residue (DGBC), tylosin fermentation residue (TLBC), and corn straw (YMBC) on the performance of AD employing food waste (FW) were compared in the current study. The results obtained from sequential batch experiments demonstrated that the addition of DGBC resulted in highest levels of methane production (161.02 mL·g −1 ), which could quickly stabilize after the fluctuation of environmental pH, revealing a certain ability to regulate acidification. Moreover, DGBC effected the enrichment of hydrolytic acid–producing bacteria and methanogenic archaea to accelerate the transformation of organic matter. Additionally, the presence of Syntrophorhabdus , an electroactive microorganism, indicated that DGBC potentially generated methane via electron transfer. Overall, the current study demonstrated that porous DGBC rich in alkali and alkaline earth metals was conducive for both methane production and the stable operation of AD systems by enhancing the activity of anaerobic microorganisms as well as accelerating substrate utilization and transformation. Graphical Abstract Highlights The abundant pore structure and alkali metal elements in DGBC facilitated enrichment of hydrolytic bacteria and methanogens. The presence of electroactive microorganism demonstrated the potential of DGBC to facilitate interspecific electron transfer. DGBC enhanced the abundance of genes associated with the acetate and hydrogen methanogenic metabolic pathways (mtrA, mtrD).