Biomass energy

Biomass is a generic term for plants that are grown for energy generation. This can be in the form of wood, plant oils, straw and other natural plant materials. The main positive of using biomass is that it is carbon neutral, i.e. the carbon dioxide given off when burning the biomass is equal to the amount of carbon dioxide absorbed by the plant during its life.

The main sources of biomass fuel is wood. This comes in a variety of formats: logs, chips and pellets. These have different applications depending on the management of the building.

Logs are the easiest to manufacture and so have the lowest embodied energy, however they are more difficult to transport and to feed into boilers. They are commonly used more for decorative fires or in large industrial boilers.

Chips are still quite bulky and have to be actively fed into boilers either through gravity or by mechanical means. This makes them ideal for larger applications and many schools are now being fuelled by woodchip.

Wood pellets are the most energy intensive, as they go through the most processing, however they then can be used domestically since biomass pellet boilers are gravity fed with a large-ish hopper that is enough for up to a week's worth of fuel. These boilers are no bigger than a conventional gas or oil boiler, but are floor mounted rather than wall hung.

Boiler technology is such that these biomass boilers are very efficient (comparable to condensing gas boilers), programmable and easy to use. The only constant is the issue of storage of the fuel. A minimum of 1 tonne of fuel should be allowed for, since if less is bought then transport costs really start to make the option less viable.