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.
BSI recommends this version of standard for organisations operating in or with the UK. The ISO edition is available here if required.