The influence of biochar amended dewatered fresh sewage sludge (DFSS)-wheat straw co-composting on nutrients transformation and end products quality was investigated. This is the first study to examine the biochar applied compost quality with different kg ha (1) TKN on Brassica rapa L. growth. Seven mixtures were composted over 8-weeks period in 130-L reactor using the same DFSS with different concentration of biochar (2%, 4%, 6%, 8%, 12% and 18% on dry weight basis) and without additive added treatment served as control. The results indicated that compost with 8-12% biochar became more humified within 35 days of composting, and the compost maturity parameters also showed that this could be much more feasible approach to increased water-soluble nutrients including NO3, DOC, DON, PO43 ,K+ and Na+, but bioavailability of Cu, Zn, Ni and Pb content reduced as compared to control. Finally, results showed that 8-12% biochar was recommended for DFSS composting and 150 kg ha (1) TKN of compost dosages for organic farming. (C) 2017 Elsevier Ltd. All rights reserved.