Green waste composting with bean dregs, tea residue, and biochar: Effects on organic matter degradation, humification and compost maturity

The effects of bean dregs (BD), tea residue (TR), and biochar (BC) as additives on the organic matter (OM) degradation, humification, and maturity of green waste (GW) composting was examined. A 30-day aerobic composting study was conducted using six combinations of GW, BD, TR, and BC [GW, GW+BD, GW+TR, GW+BD+TR, GW+BD+BC, GW+BD+TR+BC]. The results showed that the additive treatments promoted OM degradation. The OM degradation of the additive groups was 28.75%-51.81% higher than that of the control group (GW as the control), and the degradation of hemicellulose and cellulose was 9.48%-25.39% and 10.12%-21.19% higher, respectively. Meanwhile, the synthesis of humic substances (HS) was significantly better than that of the control treatment. Bacterial community analysis showed that optimized composting increased bacterial community diversity. In addition, the amended composting enhanced maturity indices, including the C/N ratio, cation exchange capacity (CEC), germination index (GI), and electrical conductivity (EC). Canonical correlation analysis (CCA) suggested that the GI and CEC were positively correlated with HS but negatively correlated with the OM concentration. The evaluations of OM degradation, humification, bacterial dynamics, and maturity indicated that the GW+BD+TR+BC treatment was the best for improving GW composting and achieved an optimal maturity and stability. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The addition of bean dregs, tea residue, and biochar can promote the degradation and humification of organic matter in green waste composting, increasing the synthesis of humic substances and improving maturity indicators. Molecular analysis and bacterial community changes indicate that optimized composting not only increases diversity but also enhances compost stability, making the GW+BD+TR+BC treatment the most effective combination for improving composting outcomes.