Synergistic application of biochar and compound microbial inoculant improves the performance of green waste composting.

Composting of green waste (GW) is a sustainable strategy for organic waste recycling; however, its efficiency is often constrained by the recalcitrant nature of lignocellulosic components. This study evaluated the synergistic effects of biochar (BC) and a compound microbial inoculant (VT) on lignocellulose degradation and overall composting performance. Nine treatments were established with varying BC (0 %, 3 %, and 6 %) and VT (0 %, 0.2 %, and 0.4 %) additions over a 35-day composting period. Among all treatments, the co-application of 6 % BC and 0.2 % VT (T8) produced the greatest improvement, with the highest peak temperature (PK, 63.7 °C), an extended thermophilic phase of 8 days and a shortened composting duration of 26 days. The sustained high temperatures enhanced lignin peroxidase, laccase and cellulase activities, which promoted lignin, cellulose and hemicellulose degradation by 22 %, 27 % and 12 %. At the same time, T8 improved nutrient retention, increasing total nitrogen, phosphorus and potassium by 22 %, 27 % and 12 %, and supporting stronger organic matter (OM) mineralization that contributed to a higher germination index (129 %). BC improved the composting environment by enhancing aeration, increasing water permeability, and moderating pH, thereby supporting microbial activity, while VT strengthened lignocellulolytic enzyme secretion. Their synergistic interaction regulated carbon-nitrogen turnover, enhanced OM mineralization, and reduced nutrient loss. These findings demonstrate that coordinated BC-VT application can create a more favorable composting microenvironment, accelerate lignocellulose decomposition, enhance nutrient retention, and improve final compost quality. This synergistic approach offers a promising strategy for efficient and sustainable GW composting and resource utilization.