Distribution of C and N in soluble fractionations for characterizing the respective biodegradation of sludge and bulking agents

► Routine C/N ratio is not a sensitive parameter to characterize the biodegradation. ► Distribution of C and N in soluble fractionations gave an insight of degradation. ► For sludge, 36.9% of C loss and 52.4% of N loss were contributed by W35 °C. ► For straw, 22.4% of C and 89.8% of N lose in W35 °C. ► HEM and CEL fraction of straw contributed a lot to C loss, while little to N loss.