Selective enhancement and verification of woody biomass digestibility as a denitrification carbon source

•Combined lime and peracetic acid was efficient pretreatment for sawdust.•Carbon digestibility was enhanced 1–21.8 times under controllable conditions.•The DOC released was positively correlated with the carbon source digestibility.•Carbon source with appropriate digestibility improved denitrification efficiency. The denitrification efficiency of woody biomass as carbon source is low because of its poor carbon availability. In this study, representative poplar sawdust was pretreated with lime and peracetic acid to enhance the biomass digestibility to different degrees; sawdust was then mixed with soil to investigate its denitrification efficiency. Under controllable conditions (25–95°C, 12–24h, varying dosages), sawdust digestibility (characterized by reducing sugar yield) was selectively enhanced 1.0–21.8 times over that of the raw sawdust (28.8mgeq.glucoseg−1 dry biomass). This increase was mainly attributed to the removal of lignin from the biomass. As a carbon source, the sawdust (digestibility enhanced by 5.4 times) increased the nitrate removal rate by 4.7 times, without N2O emission. However, the sawdust with high digestibility (12.6 or 18.0 times), despite releasing more dissolved organic carbon (DOC), did not exhibit further increase in denitrification efficiency, and emitted N2O.