To help with the use of the information, guides and materials produced in FOREST, we have produced a Glossary defining the commonly-used terms throughout the site.

Accumulator

A water-storage tank which is integrated into the heating system, used to collect and store heat energy and smooth out demand variation.

Arboriculture

Cultivation of trees and shrubs, and the study of how they grow and the environment they grow in. Arboricultural arisings can be a source of low-quality wood fuel, with high moisture content.

Ash

Ash is a non-combustible, mineral content of biomass formed during combustion. There are two types: bottom (or bed) ash left behind, in or under the grate. It can melt or fuse, when it is then referred to as slag or clinker. The other type of ash is the very small particulate type, carried out of the system along with the flue gases. This is referred to as fly ash, and can be removed by filtering.

Auger

Corkscrew type feed mechanism for automatic transfer of chip or pellet to the boiler.

Agitator

A rotating arm at the base of the fuel store to prevent bridging and maintain consistent feedstock to the auger.

Buffer Tank

A small thermal store used to absorb the output of a the boiler during shut down, and provide initial heat from stored capacity on start up whilst boiler comes up to operating temperature.

Base Load

The minimum heat demand from a system which is
maintained throughout a defined period.

Batch Boiler

A (typically) log boiler that will fully burn the fuel load for a period of time, with the output typically being used to heat a thermal store to meet daily demand.

Back Boiler

A small water boiler for domestic hot water fitted to stoves used for hot water and central heating.

Biomass Energy Centre (BEC)

The Forestry Commission’s UK Centre of Expertise on Biomass.

Briquette

Larger log-type fuel made from compressed sawdust/co-product/energy crop.

ConFor

Confederation of Forest Industries –Trade Association for Commercial Forestry in the United Kingdom.

Co-Product

Wood fuel produced as a secondary product from virgin timber that is ‘clean’ wood (i.e. sawdust from saw mill activity made into pellets, or fro tree felling).

Energy Crops

Crops grown specifically for dedicated energy production purposes (e.g. miscanthus).

ESCO

Energy Supply Company – contracts to supply heat to the end user, and may or may not own, operate and maintain boiler as well as supplying fuel.

Forestry Commission

The United Kingdom Government Agency responsible for strategic direction and management of Woodland.

Heat Log

Another word for Briquette.

Renewable Heat Incentive (RHI)

A new UK scheme to give payments to the end user of renewable heat rather than a grant for installation, due for introduction in 2011.

Short Rotation Coppice

Fast growing wood fuel crops, such as Willow.

Slabwood

The offcuts from sawmilling of felled trees – a useful co-product for wood fuel.

Stove

An enclosed fire.

Space Heater

A hot/warm air stove that heats room through convection.

Thermal Store

A large heat store (hot water) used to balance the overall heat load of the system, allowing a smaller size boiler to run more efficiently over a daily cycle. Often run with a buffer vessel, which can also be integral to the thermal store. Thermal stores can also contain multiple heating cols to allow other heating systems (such as solar thermal panels) to be integrated.

Waste Wood

Wood that is used for wood fuel that has been contaminated in some way in its primary use (i.e. painted timber, demolition timber), which if used as fuel, needs to be burnt in conditions that conform to the Waste Incineration Directive.

Wood Chip

Wood fuel of a certain size and quality suitable for auger – type mechanisms to automatically feed into boilers.

Wood Pellet

Co-Product compressed so that natural bonding agents within the wood bind it together into uniform sized fuel pieces that are suitable for automatic handling. Have a higher energy density than woodchip, and is suitable for smaller/restricted sites.