Burning wood to provide domestic heating is hardly a new phenomenon: we humans have been doing it for about half a million years. Indeed, the Western world’s love affair with fossil fuels began in earnest little more than 150 years ago when coal and, later, oil became widely available. In that short span of time, however, the use of wood as a primary source of energy for domestic heating in Britain has all but disappeared.
Log fires and wood-burning stoves may add warmth and character to country homes but rarely are they used to do other than provide additional space heating in the principal living rooms. In most houses the bedrooms, bathrooms, halls, kitchens, offices and utility rooms are heated via radiators by a central heating boiler which burns either oil or gas.
Central heating technology has been designed around the convenience of these two fuels. They are clean, easy to store and to pipe to the point of combustion, have a high calorific value and are easily delivered. But they mostly have to be imported from overseas, are expensive and will get more so as world supplies start to run out. And, as nobody who so much as looks at a newspaper will have missed, burning oil and gas is responsible for adding large amounts of carbon dioxide (CO2) to the atmosphere.
The latter disadvantage is true, of course, for wood. However, the thing about wood fuel is that it is a renewable resource. Yes, it kicks out a whole lot of CO2 when you burn it. But when it grows, most of that CO2 is sucked straight back out of the atmosphere and photosynthesised into oxygen and a new supply of carbon-based fuel. As a result, burning wood produces about 97 per cent less carbon emission into the atmosphere than fossil fuels.
In some Western countries such as Austria, where there are plenty of productive forests and the tradition of using wood fuel has not been lost, modern central-heating technology has been applied to the age-old practice of burning timber in the home, and the result has been a completely new generation of wood-fired boilers. They are highly efficient, extracting more than 90 per cent of the heat energy from the fuel. Furthermore, they produce virtually no ash or smoke and they are fully automatic. Wood chips or pellets are delivered to the combustion chamber by means of an auger and are electronically ignited when the boiler’s temperature drops below a pre-set level.
For the estate owner with plenty of timber or forest thinnings, the new generation of wood-fuelled boilers has obvious advantages. With the help of a mobile chipper and a front loader, a couple of days’ work will provide all the fuel needed for an entire year. Woodchip is bulky but if you’ve got the space, you can store it like grain in a hopper or floor store, and once it is below about 30 per cent moisture content it will burn cleanly and efficiently. So you can run the heating all day without burning a hole in your pocket – and feel virtuous?
Hi-tech wood fuel poses slightly more complex problems for those who do not own extensive woodlands, and the question of continuity of fuel supply was the main reason why I hesitated before installing a wood-fuelled boiler in the new commercial barn conversion on my farm in Suffolk. Any number of local oil suppliers will turn up in my yard at 48 hours’ notice; woodchip suppliers, on the other hand, are notably absent from Yellow Pages. But when Suffolk County Council replaced the oil-fired central heating boilers in a number of its primary schools with wood-fuelled ones, I realised there was some guarantee that commercial supplies of wood fuel would be available locally, at least for the foreseeable future.
Slowly but surely, wood fuel is making an impression in Britain, and particularly East Anglia. The National Trust (NT) installed a 60kW wood-burning central heating system in its new regional headquarters near Bury St Edmunds in 2004. The centre, a block of converted farm buildings, is heated with softwood thinnings from the Trust?s Ickworth estate two miles away. Timber is felled in March and stored by the roadside until September when it is chipped and stored. Woodchip is delivered to a top-fed hopper adjacent to the boiler once a week in winter and once every eight weeks in summer, and a bucketful of ash is removed from the boiler once a week during peak usage.
In 2005 Roger Combe, owner of Bayfield Hall in north Norfolk, installed a 60kW boiler to heat the 12-bedroom hall, a four-bedroom self-contained flat and approximately 190sq metres of converted stable block. Wood is harvested from the estate or other local properties and chipped, and the house is heated 24 hours a day and has unlimited quantities of hot water.
Both the NT and the Bayfield projects were installed by Bedfordshire-based Econergy. When considering a wood-fuelled installation for Bridge Farm, Chediston, in north Suffolk we looked locally for an installer and found Energy Innovations, near Woodbridge, which proposed a 45kW boiler manufactured by the Austrian firm Gilles to supply the underfloor heating, radiator circuits and hot-water system for our barn development, and came up with an ingenious means of delivering the woodchip.
Our problem here was that the only possible location for our fuel hopper was immediately adjacent to the barn within a range of traditional, tiled cart lodges, so there was no prospect of using a tractor and front loader to fill it from above. Instead, Energy Innovations fitted a pneumatic filling system whereby woodchip is blown from the delivery truck via a 6in-diameter flexible pipe. Thanks to this method we were able to accommodate the 22m3 hopper within the cart lodge. Clad with weatherboarding, it blends perfectly with the adjacent barn.
The boiler and associated works were commissioned in May 2007 with the aid of a capital grant from the then Department of Trade and Industry?s Low Carbon Building Prog-ramme stream 2A. Even with grant aid, the cost was two or three times that of an oil-fired system, and there is an element of blind faith that reduced fuel costs will in due course repay the higher capital outlay. Altruism and commitment to reducing one?s carbon footprint are all very well, but wood-fuel technology can take off only if it makes genuine business sense.
At present oil costs around 3.4p per kW/h with gas at 3.2p. Wood pellets from sawdust and pulverised wood waste cost about 2.9p, reflecting the high calorific value of this fuel and the cost of pellet production. Pellets are a tempting option but there are no local manufacturers: supplies to East Anglia come from Ireland. Woodchip should cost around 1.8p, but the limited number of producers in the region means added transport costs. There is thus a real opportunity for estate owners to produce woodchip for commercial supply in their neighbourhood.
Woodchip for the open market will have to meet reasonable standards of calorific value and moisture content, but with the establishment of a regional supply network there should be the real prospect of sourcing renewable central heating fuel from local woodlands.
Get fired up
Biomass Energy Centre Advice on using, producing and supplying wood fuels, legislation and grants; Biomas Energy Centre.
Anglia Woodfuels A wood fuel supply producer group in the East of England. It offers a wood fuel chipping service to woodland
owners, technical advice/support; Anglia Wood Fuels.
Grant availability National funding from Defra’s Bio-energy Capital Grants Scheme, the third round of which was launched in December 2006. Subsequent rounds are intended. For current status visit DEFRA (can be found via www.biomassenergycentre.org.uk). Funding may be available from your regional Development Agency.