OpenLB
Open Library of Bioscience

The composting process is accompanied by CO and CH emissions, leading to environmental pollution and lower fertilizer efficiency. Biochar has been widely applied to mitigate CO and CH emissions, while its effect when added at different composting stages is till unclear. Therefore, this study investigated the effects of biochar added on day 0, 10, or both days on CO and CH emissions during composting process, and explored the mechanisms from multiple aspects including physicochemcial properties of compost matrix, degradation of organic matter (OM) components, functional enzyme activities and genes abundances. The findings showed that biochar enhanced the activities of lignocellulolytic enzymes, thus facilitating the degradation of cellulose, hemicellulose and water-soluble organic carbon (WSOC). All biochar addition strategies resulted in higher CO emissions and C cycling genes abundances, while addition of 5% or 10% biochar on day 10 effectively reduced CH emissions by 17% and 50%, respectively. Mantel analysis and partial least squares path modeling revealed that OM components played the primary role in influencing CO emissions , with physicochemical properties, such as temperature, C/N and pH, playing a secondary role by influencing the degradation of OM and WSOC, while no significant factors were found to directly affected CH emissions. Moreover, the lignocellulolytic enzymes and C cycling genes did not show significant impacts on their emissions. This study provides important insights for improving the mitigation on CO and CH emissions by biochar.