This International Standard describes methods for the determination of sulfur and chlorine content in solid biofuels and pyrogenic biocarbon and specifies two methods for decomposition of the fuel and different analytical techniques for the quantification of the elements in the decomposition solutions. The determination of other elements such as fluorine and bromine is also possible with the methods in this document, however performance data for these elements are not provided. The use of automatic equipment is also included in this International Standard, provided that a validation is carried out as specified and that the performance characteristics are similar to those of the method described in this International Standard.