Enhancing compost quality: Biochar and zeolite's role in nitrogen transformation and retention

This research evaluated how addition of biochar and zeolite affected nitrogen transformation and retention during the composting of kitchen waste. Four treatments, control (CK), 10 % biochar (B), 10 % zeolite (Z), and 5 % biochar +5 % zeolite (BZ) were used to study nitrogen transformation and retention. The results showed that biochar and zeolite can significantly reduce the loss of NH₄⁺-N during the thermophilic phase (CK: 42.6 %, B: 35.1 %, Z: 35.7 %, and BZ: 31.3 %). Network analysis showed that biochar and zeolite increased the number of microorganisms associated with nitrification genes while decreasing the number of microorganisms associated with denitrification genes, preventing nitrogen volatilization in N₂O. Mantel tests further demonstrated that biochar and zeolite enhanced the correlation between bacterial communities and the relationship between NH₄⁺-N, NO₃^--N, and organic nitrogen was weakened, thus inhibiting the mineralization of organic nitrogen. Therefore, biochar and zeolite played an active role in promoting the transformation and retention of nitrogen components. Biochar and zeolite for kitchen waste also provided a new perspective on the treatment of kitchen waste.