Terminology

Archimedes screw (auger) - rotating spiral of metal inside a tube used in boiler feed mechanisms for woodchips or pellets, and in automated ash extraction mechanisms.

Auger (Archimedes screw ) – rotating spiral of metal inside a tube used in boiler feed mechanisms for woodchips or pellets, and in automated ash extraction mechanisms.

Biodiesel – diesel made from biomass, such as oilseed rape.

Bioenergy – a term used to describe energy produced from biomass. Sometimes describes potential energy within biomass.

Bioethanol – ethanol made from biomass.

Biofuel – term generally used to encompass liquid fuel made from biomass, such as biodiesel or bioethanol.

Biomass – potential fuel energy in the form of biological material such as timber, miscanthus, dung or straw.

Boiler – device for extracting heat energy from fuel to provide hot water or steam.

Briquette - larger diameter cylindrical section of compressed dried sawdust used as fuel in a similar way to logs.

Bulk density – the weight per unit volume for a solid materials.

Calorific value – the amount of heat produced by the complete combustion of a unit weight of fuel, often expressed in megawatt hours per cubic metre.

Chipper – machine, mobile or static, used for the production of woodchips.

Chipping – the process of making small fragments of timber (usually to a specified size) by passing larger logs or pieces of timber through a chipper.

Chips – (shortened form of woodchips) small fragments of timber sliced from a larger log or piece of timber by a chipper, usually to a specified size.

Combined heat and power (CHP) – a term used to describe systems that derive and utilise both thermal and electricity energy from a given fuel source.

Combustion – the process of converting fuel into heat energy.

District heating scheme – system by which heat is distributed via underground pipe-work from a single centralised boiler to a number of individual users, usually domestic dwellings.

Energy crop – typically a crop of trees, woody plants or grasses grown for the purpose of providing biomass for energy.

Flue – a chimney-like tube for the venting of gases and vapour from the boiler after combustion.

Fossil fuels – fossilised fuel such as coal, mineral oil and natural gas. When burnt fossil fuel releases carbon into the atmosphere that has been trapped beneath the earth’s surface for millions of years. Thus fossil fuel use can contribute to an increase in current atmospheric greenhouse gases and lead to global warming.

Gas turbine – device for turning thermal energy from gasified biomass into electrical energy.

Gasification - conversion of solid material such as woodchip into a gas for use as a fuel.

Heat exchanger – device, within a boiler or water tank, to transfer heat from one system to another.

Hopper – fuel storage container usually adjacent to a boiler house.

Kilowatt – a unit of energy equal to 1000 watts.

Kilowatt hour (Kwh) – the basic unit of energy equal to 1 kilowatt or 1,000 watts of power used for one hour. A single bar electrical fire would typically use about 1 kilowatt hour (kwh) of electricity if operated for 1 hour.

Logs – section for a tree or branch cut/split to a specified length for use in a wood burning stove or automated log boiler.

Megawatt - unit of energy equal to one million watts, or one thousand kilowatts.

Megawatt hour (Mwh) - measure of energy production or consumption equal to one million watts produced or consumed for one hour (equal to 1000 kilowatt hours).

Miscanthus – a grass often planted as an energy crop.

Moisture content (mc%) – the percentage by weight of water in a material.

Oven dry tonne (odt) – 1 tonne of material (woodfuel) at 0% moisture content.

Pellets – small diameter cylindrical section of compressed sawdust formed by passing dry sawdust under high pressure through a dye. Usually between 6-8mm in diameter and 10 to 30mm in length.

Pyrolysis – the chemical decomposition of woodchips by the action of heat to produce a liquid fuel.

Silo – fuel storage container usually adjacent to a boiler house, can be below ground.

Solid fuel – fuel in solid form, typically wood or coal, often used in stoves, open fires and some boilers.

Steam turbine – device for converting thermal energy from steam into electrical energy.

Stove – device for use indoors to provide room heat, usually from solid fuel.

Watt - a unit of energy defined as one joule transferred or dissipated in one second.

Woodchips - small fragments of timber sliced from a larger log or piece of timber by a chipper, usually to a specified size.

Carbon emissions – term generally used to describe the level of carbon, usually in the form of carbon dioxide, exhausted into the atmosphere by a process.

Carbon neutral (low carbon) – a term used to describe processes that have a zero or very low contribution to atmospheric carbon. Using woodfuel for heat and power can be described as carbon neutral because the carbon emitted during combustion is equal to the carbon absorbed by the trees when they were growing.

Fossil fuels - fossilised fuel such as coal, mineral oil and natural gas that, when burnt, releases carbon into the atmosphere that has been trapped beneath the earth’s surface for millions of years. Burning fossil fuel can contribute to an increase in atmospheric greenhouse gases.

Global warming – the rise in the earth’s atmospheric temperature. Consider to be partly due to man-made atmospheric pollution contributed to by the use of fossil fuels.

Greenhouse Gas (GHG) – gas capable of absorbing infra-red radiation before it escapes the earth’s atmosphere (e.g. carbon dioxide, methane).

Renewable energy – energy that has been obtained from a potentially infinite resource such as wood, sunshine or the wind.

Renewable fuel – fuel that is considered to be an infinite resource if its source is sustainably managed. Examples can include woodfuel, miscanthus or the wind.

Sustainable - meeting the needs of the present without compromising the ability of future generations to meet their needs.
Sustainable forest management – the process of managing forests to provide goods and services without degradation of the site quality, and without a decline in the yield of goods and services over time. These goods and services can be disparate and may include, for example, timber, amenity value, inherent biodiversity, landscape value (see ‘sustainable’).

Arboricultural arisings – woody material produced during arboriculture.

Arboriculture - the management of individual trees or groups of trees primarily for their amenity value.

Brash – the branch-wood and leaf material that is generally too small in diameter to be considered part of the timber product from a harvesting site.

Clear felling – term used to describe a harvesting operation that removes all the trees from a given area.

Clones – genetically identical trees propagated commercially because of desirable properties. Often used in, for example, short rotation coppice.

Coppice – the practice of harvesting the above ground part of a tree for timber and allowing the new shoots to regrow in a cycle normally extending over a number of years.

Crop – a term used to collectively describe the trees in a productive woodland.

Felling – the cutting of standing trees.

Forward – the process of extracting harvested timber from a woodland whilst keeping the timber off the ground (involving a tractor and trailer unit known as a forwarder).

Hag - the branch-wood and leaf material that is generally too small in diameter to be considered part of the timber product from a harvesting site.

Harvesting - the practice of felling and removing trees from a woodland.

Haulage – the movement of timber from site to site, usually by lorry.

Log – a product of normal forestry harvesting operations; sections of a tree cut to a specific length.

Lop & top - the branch-wood and leaf material that is generally too small in diameter to be considered part of the timber product from a harvesting site.

Rotation – the period of growth of a forest crop before it is considered mature.

Short rotation coppice – the practice of growing and harvesting the above ground part of a crop, usually of willow, for biomass and then allowing new shoots to regrow from the harvested stumps (also known as stools) in a short cycle (3 to 5 years).

Short rotation forestry – the practice of growing a specific crop of trees, usually poplar, for biomass over a relatively short rotation (usually no more than 15 years).

Silviculture – the care and cultivation of forests.

Skid – the process of extracting timber from a woodland site by winch, usually dragging part of the timber on the ground.

Thinning – the process of removing selected trees from an immature woodland to allow other trees to increase in diameter.

Yield – the timber volume increment of a specified area of woodland over a specified time. Usually expressed in m³/ha/year.