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Wood Fuels

wood burning stoveWood or fuel derived from wood is often called biomass. It is included as renewable energy because it is organic matter of recent origin. It doesn't include fossil fuels, which have taken millions of years to be created. The CO2 released when biomass fuels are burned is balanced by that absorbed while the wood was growing in the recent past. This is therefore, at least in theory, a carbon neutral process.

There are many wood burning boilers and stoves available, and the fuel takes the form of wood pellets, wood chips or wood logs.

There are two main ways of using biomass to heat your home:

  • Stand alone stoves providing space heating for a room. These can be fuelled by logs or wood pellets but only pellets are suitable for automatic feed. Generally they are 6-12 kW in output, and some models can be fitted with a back boiler to provide water heating.
  • Boilers connected to central heating and hot water systems. These are suitable for pellets, logs or chips, and are generally larger than 15 kW.

What are the costs and savings?

Stand alone pellet stoves generally cost around £3000-£5000 installed, while log-burners are much less expensive. Savings will depend on how much they are used and which fuel you are replacing. The cost for a typical 15kW (average size required for a three-bedroom semi detached house) pellet central heating boiler is around £7000 - £12,000 installed, including the cost of the flue. For larger properties, the total could exceed £20,000. A manual log feed system is slightly cheaper.

A biomass powered boiler could save you anything from £100 to over £500 per year in energy bills, depending on what type of fuel it replaces, and up to around 8 tonnes of C02 per year. The Energy Saving Trust gives more details on costs and savings. Beware that biomass is relatively more expensive to run than an oil-fired boiler of the same capacity, but will give considerable carbon savings.

Incentives for installing biomass boilers

Apart from their environmental benefits, biomass boilers and certain types of biomass stoves qualify for payments under the domestic Renewable Heat Incentive. Payments typically are in the range £500 to £1200 per year.

Important Points

  • Log boilers must be loaded by hand and may be unsuitable for some situations.
  • According to building regulations the top opening of the boiler flue or chimney must be at least 4.5 m above the top of the appliance, and ideally should rise straight up to near the roof ridge to end at least 600 mm above the roof ridge.
  • A carbon monoxide alarm should be fitted in any room containing a wood-burning or multi-fuel-burning appliance.
  • Automatic pellet and wood chip systems are more expensive.
  • Many boilers are suitable for both wood chips and pellets, although the wood chip boilers need larger hoppers
  • Consult an accredited installer to provide more detailed advice.
  • It is most cost effective when a local fuel source is used, which results in local investment and employment and also minimises transport miles to your home. Wood pellets currently need to be imported, but can be delivered in the Stafford area.
  • To qualify for payments under the Renewable Heat Incentive, from October 2015 the fuel must meet certain sustainability criteria.
  • You need storage space for the fuel
  • Unlike other forms of renewable energy, biomass systems require you to pay for the fuel, rather than using free energy from the sun, wind, earth etc.