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 sulphate. 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 EN 12880).