This document specifies a method for the determination of the content of heavy extraneous materials (HEM) larger than 3,15 mm by the use of sink-and-float separation combined with elutriation. This document is applicable to woody biomass in accordance with ISO 17225-1, and especially for hogfuel in accordance with ISO 17225-9.

NOTE 1        This method is designed to determine the level of impurities larger than 3,15 mm with a specific density >1 g/cm3, such as stones, glass, rubber, metal and certain types of plastics.

NOTE 2        During the processing of the sample, hand sorting of light impurities with a specific density ≤1 g/cm3 (e.g. plastic foil) can also be done.

NOTE 3        Some heavy extraneous materials (e.g. lumps of clay) can fall apart when submerged in water.

NOTE 4        Heavy extraneous materials smaller than 3,15 mm can damage milling equipment, when reducing the material in size to produce laboratory samples.