Table 2.

Flow classes.

Flow Class	Resource/Emission	Definition	Example Flowable(s)
Biological	Both	Biomass or organic matter (i.e., microorganisms)	‘Wood’ or ‘Bacillus subtilis’
Element or Compound	Both	A unique chemical element or compound	1,1,2,2-Tetrachloroethane
Energy	Both	Energy input NOT associated with consumed materials including heat	Energy, Geothermal
Geological	Both	A mineral or metal in an ore or aggregate material extracted for use or refining	Anthracite
Groups of Chemicals	Both	A group or mixture of chemicals	Dioxins
Land Use	Input	Land types	Land
Water	Both	Water	Water, fresh
Other	Both	None of the above. May include water quality parameters	Biological oxygen demand