The aim of this study was investigated the effects of acidic additives apple pomace (AP), citric acid (CA), elemental sulphur (ES), phosphoric acid (PA), magnesium hydrogen phosphate (PM), and calcium superphosphate (CP)) on N conservation and greenhouse gas (GHG) emissions during sewage sludge composting. Results showed that adding the additives have no negative effects on compost hygienisation, but could improve the N conservation. Treatments with additives showed 2.56-5.48% N loss of initial N, which is lower than the control (9.73%). Compared to other compost products, ES-and PA-treatments had the lower NH3 volatilizations (0.80% and 0.98% of initial N, respectively) and germination index values (0.52 and 0.74, respectively), while the higher N2O emissions (2.48% and 2.29% of initial N, respectively) and salinities. Comprehensive evolution of N loss, GHG emissions and compost maturity in this study, the feasibility of using AP, CA, and PM in high-quality compost production is promising.