Nitrification plays a key role in N2O emission in electric-field assisted aerobic composting

[Display omitted] •Electric field applications inhibited nitrification in composting.•Electric-field assisted composting promoted nosZ expression.•N2O was mainly from nitrification in electric-field assisted aerobic composting. Nitrous oxide (N2O) emission is a serious environmental problem in composting. Previous studies have indicated that electric field assistance results in lower N2O emissions in aerobic composting; however, the exact mechanisms involved in electric-field assisted aerobic composting (EAAC) are not clear. In this study, the biological N transformation processes and the N-associated genes were investigated. The results demonstrated that electric field application inhibited nitrification, weakened the nitrifying functional genes (the hao and nxrA genes declined maximally by 86% and 86.8%, respectively), and increased the N2O consumption-related gene (nosZ) by a maximum factor of 2.76 compared with that in CAC. The correlation analysis demonstrated that nitrification was the main source of N2O emission in EAAC. The findings imply that EAAC is a promising process for mitigating N2O emission at the source during aerobic composting.