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2. Definition of i-WESTAT items and conversion factors

The woodfuel types and flows that compose the “items” of the i-WESTAT database refer to the definitions formulated in the Unified Bioenergy Terminology and summarized in the following figure.

Woodfuel balance scheme, from supply source to end user

Definition of relevant terms

The following is a selection of the more relevant terms from the Unified Bioenergy Terminology.

black liquor

alkaline spent liquor obtained from digesters in the production of sulphate or soda pulp during the process of paper production, in which the energy content mainly originates from the content of lignin removed from the wood in the pulping process


solid residue derived from carbonization distillation, pyrolysis and torrefaction of fuelwood

energy density

ratio of net energy content and bulk volume

NOTE The energy density is calculated using the net calorific value determined and the bulk density


cut and split oven-ready fuelwood used in household wood-burning appliances such as stoves, fireplaces and central heating systems. Firewood usually has a uniform length, typically in the range 150 to 500 mm.


energy carrier intended for energy conversion


woodfuel where the original composition of the wood is preserved

gross calorific value (qgr)

absolute value of the specific energy of combustion, in joules, for unit mass of a solid fuel burned in oxygen in a calorimetric bomb under the conditions specified. The results of combustion are assumed to consist of gaseous oxygen, nitrogen, carbon dioxide and sulphur dioxide, of liquid water (in equilibrium with its vapour) saturated with carbon dioxide under conditions of the bomb reaction, and of solid ash, all at the reference temperature and at constant volume. The old term is higher heating value

NOTE Adopted by ISO1928:1995

net calorific value (qnet)

under such conditions that all the water of the reaction products remains as water vapour (at 0.1 MPa), the other products being as for the gross calorific value, all at the reference temperature. The net calorific value can be determined at constant pressure or at constant volume. The old term is lower heating value. Net calorific value as received (qnet,ar) is calculated by the net calorific value from dry matter (qnet,d) and the total moisture as received

oven-dry wood

wood free of moisture, produced by drying to constant weight under specific conditions

recovered construction wood

used wood arising from construction of buildings or from civil engineering works


fine particles created when sawing wood

NOTE Most of the material has a typical particle length of 1 to 5 mm


parts of woody biomass created when cuts are made into the edges of logs and whereby one side shows the original rounded surface of the tree, either completely or partially, with or without bark

stacked volume

volume of stacked wood including the space between the wood pieces

used wood

wood substances or objects which have performed their intended purpose

NOTE 1 See also recovered construction wood and demolition wood

NOTE 2 Proposal within the Draft CEN Report Solid Recovered Fuels [11]

wood chips

chipped woody biomass in the form of pieces with a defined particle size produced by mechanical treatment with sharp tools such as knives. Wood chips have a sub-rectangular shape with a typical length 5 to 50 mm and a low thickness compared with other dimensions

NOTE See also cutter chips, forest chips, green chips, stemwood chips, and whole-tree chips.

wood energy, forest energy

energy derived from woodfuels corresponding to the net calorific value of the fuel

wood energy systems

All the (steps and/or) unit processes and operations involved for the production, preparation, transportation, marketing, trade and conversion of woodfuels into energy

woodfuels, wood based fuels, wood-derived biofuels

all types of biofuels originating directly or indirectly from woody biomass

NOTE See also fuelwood, forest fuels, and black liquor.

wood processing industry by-products, wood processing industry residues

woody biomass by-products originating from the wood processing as well as the pulp and paper industry

NOTE See also bark, cork by-products, cross-cut ends, edgings, fibre board by-products, grinding dust, particle board by-products, plywood by-products, sawdust, slabs and wood shavings

wood shavings; cutter shavings

shavings from woody biomass created when planning wood

woody biomass

biomass from trees, bushes and shrubs

NOTE See also forest wood, wood processing industry by-products, fibre board by-products, particle board by-products, plywood by-products and used wood

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