This method describes a procedure for the determination of ""Kjeldahl Nitrogen"" in sludge and sludge products. The digestion is catalysed by selenium or copper, the temperature being raised by a high concentration of sodium sulfate. Although wet samples are normally taken for analysis, it is recognised practice to report results on a dry mass basis (g/kg). Consequently, it is also necessary to determine the dry residue of the homogenised sample used for analysis (see prEN 12880:2000)