Partitioning Ganoderma lucidum residue biochar differentially boosts anaerobic fermentation performance of cow manure via mediation of anaerobic microbiota assembly

Biochar is a promising strategy to solve the problem of low efficiency and ammonia inhibition during anaerobic digestion (AD). However, the correlation between biochar partitioning and its stimulatory effects on AD remains uncertain. Here, the effects of partitioned Ganoderma lucidum residue biochar (GLRB) on biogas and methane production were investigated. The GLRB produced at 450 °C, with richer functional groups on its surface, had the optimal enhancement effect on AD, resulting in a 20.59% increase in methane production compared with control. The doses of water-soluble GLRB (LZ450-W) and water-insoluble GLRB (LZ450-R) were not proportional to their enhancement effect on AD. However, the enhancement effect on AD by LZ450-R was better than that of LZ450-W. The optimal dosage of LZ450-W was 0.015 g, which increased methane production by 14.28%. Similarly, methane production increased by 26.91% with the addition of 0.603 g of LZ450-R. LZ450-R had more abundant functional groups on the surface and promoted the abundance of bacteria in the dominant phyla Bacteroidetes, Synergistetes, and Spirochaetes, increasing the rate of hydrolysis. Additionally, methanogens such as Methanobacterium and Methanospirillum were enriched, facilitating methane production by promoting the hydrogenotrophic pathway. Methanobacterium was also negatively correlated with most acid-producing bacteria, whereas Methanobrevibacter was positively correlated with Methanosphaera, Acetivibrio, and other acid-producing bacteria. These findings provide a basis for constructing synthetic microbial communities using biochar as a carrier of microbial inoculum. [Display omitted] •Enhancement of anaerobic digestion was not proportional to GLRB dose.•Water-insoluble GLRB enhances anaerobic digestion more than soluble GLRB.•Both fractions promote efficient methanogenesis by reshaping anaerobic microbiota.•Hydrogenotrophic methanogenesis is the dominant pathway that was enhanced.