Effects of Lychee Wood Biochar and Lignin-Degrading Bacteria on Performance of Aerobic Composting Coupled with Vermicomposting for Cow Dung and Rice Husk
This study investigated the effects of lychee wood biochar and lignin-degrading bacteria on compost maturity, substance transformation, and bacterial communities during the coupled process of aerobic composting and vermicomposting of cow dung and rice husk. Four treatments were established: no addition (CK), 5% (w/w) lychee wood biochar addition (T1), 0.5% (w/w) lignin-degrading bacteria (Bacillus subtilis, Aspergillus niger) addition (T2), and combined addition of 5% biochar and 0.5% bacteria (T3). Results showed that biochar and/or bacteria addition accelerated temperature rise, extended high-temperature duration to 13 days, and increased maximum temperature. Compared to CK, T1–T3 increased organic matter degradation by 3.97%–9.56%, humic acid content by 12.30%–24.09%, available phosphorus and potassium by 14.48%–32.50% and 6.97%–18.85%, respectively. NH3 emissions were reduced by 25.86%–34.26%, while nitrate nitrogen and total nitrogen increased by 12.83%–43.34% and 5.73%–13.18%, respectively. Seed germination index improved by 11.62%–29.20%. T3 exhibited the best overall performance. During aerobic composting, biochar and/or bacteria significantly increased relative abundances of Bacteroidota, Planctomycetota, and Acidobacteriota, but effects were not significant during vermicomposting. Functional genera such as Bacillus, Pseudomonas, and Chryseolinea were enriched in both stages. The study concludes that adding 5% lychee wood biochar and/or 0.5% lignin-degrading bacteria to cow dung and rice husk in coupled composting-vermicomposting improves bacterial community structure, promotes organic matter degradation, enhances humification, reduces nitrogen loss, and accelerates compost maturity, with combined addition being most effective.