Woodfuel and other Woody Biomass

Biomass is the name given to living and recently dead organic material that can be used to create energy. This includes wood and also other plant, vegetable or animal matter. Biomass is also sometimes called ‘bioenergy’ or ‘biofuel’.

There are two main kinds of biomass. The first kind is woody biomass. This includes wood from forestry, energy crops (such as miscanthus) and short rotation coppice like willow. The second kind includes animal waste, food waste and agricultural residues. Woody biomass is of particular interest for small scale domestic users as well as businesses looking for cost effective green energy solutions.

• are there any local opportunities for using heat from woodfuel or other biomass products instead of fossil fuel?
• are any businesses or public sector buildings due for boiler replacements and have they considered biomass?
• are there any biomass resources available locally, such as unmanaged woodlands which could be brought back into management or any farms which could grow energy crops?

Considerations

In general, biomass technologies work best with fairly constant heating demand. Biomass boilers in particular are most efficient when operating close to full load. There are several things that can be done to ensure this is achieved:

Install a hot water accumulator tank as part of the system to store excess heat until needed, which allows a smaller and therefore cheaper boiler to be used. Design the biomass system to cover the main heating demand e.g. during the winter, and use another heat source, such as a small fossil fuel boiler, to meet the much lower heating demand in the summer for larger heat demands have several smaller boilers instead of one large one so that all can run when heat demand is at its highest, but not all need to run when heat demand is lower woodchips are cheaper than pellets, but have a lower energy density so need more storage space and/or more frequent deliveries. It is preferable to source a local biomass fuel supply for cost and sustainability reasons. Sufficient space for the stove or boiler and for storing the fuel is needed, as well as good access to the fuelstore for fuel deliveries. 

Also, if the project is located within a smoke control zone only certain types of stove or boiler can be installed. In the south west, a limited number of urban areas are smoke control zones.

The Technology

Biomass technologies use wood or other plant materials as fuel. Biomass stoves can provide space heating for individual rooms and water heating if they have a back boiler connected to them, while biomass boilers provide space and water heating for whole buildings or a group of buildings. Biomass heating is suitable for ‘new build’ or existing buildings.

The main fuels for biomass stoves and boilers are woodchips, pellets, or logs, with most stoves and boilers only being able to take one of these fuel types. Biomass is almost CO2 neutral as the CO2 released by burning wood is approximately equal to the CO2 absorbed by the tree when it was growing. The CO2 and cost savings from installing biomass will depend on the fuel being replaced.

Operation and Maintenance

Pellet stoves and pellet or woodchip boilers are usually automatic, while stoves are usually manual. All systems require the ash removing, although in general very small amounts of ash are produced and ash bins only need emptying once or twice a week. Fuel stocks need to be monitored.