Game changer for anaerobic fermentation of paper mulberry: Sucrose-loaded biochar enhancing microbial communities and lactic acid fermentation

[Display omitted] •Biochar promoted the in-situ enrichment of Lactiplantibacillus.•Biochar elevated acetic acid yields to 37 % during early fermentation.•The sucrose-biochar combination increased lactic acid content by 15 %.•The sucrose-biochar synergy reduced CH4 by 24.15 % in vitro rumen tests.•Biochar is a favorable strategy for anaerobic fermentation of paper mulberry. This study investigated biochar effects, either alone or combined with sucrose, on fermentation quality, microbial communities, and in vitro rumen digestion of anaerobic fermented paper mulberry. The biochar alkaline functional groups bind to lactic acid, reducing acid inhibition and promoting Lactiplantibacillus proliferation. Owing to the low sugar content of paper mulberry, lactic acid bacteria in the biochar group primarily underwent heterofermentation, resulting in the lowest lactic and highest acetic acid contents. Treated with sucrose-loaded biochar, the increased substrate supported homofermentation, leading to the highest lactic and lowest acetic acid contents, with a 15.0 % increase in lactic acid and a 22.2 % decrease in ammoniacal nitrogen compared with the control after 75 days. In vitro rumen tests showed that the biochar-sucrose group had the highest dry matter degradation rate (45.9 %) and a 24.2 % reduction in methane emissions. Concludingly, sucrose-loaded biochar is recommended as effective for lactic acid production under anaerobic conditions.