Burning trees is good for you
At least that's the theory according to farmers who are adapting the ancient art of coppicing to combat global warming. by Daniel Butler
Saturday 06 January 1996
He is convinced growing and burning wood to generate electricity is the environmentally friendly answer and has put his beliefs into practice by planting 10 hectares (24 acres) of poplar cuttings on his farm near Bath. He says wood for fuel is "green" in every way.
Maggs's conviction that burning trees is an answer to global warming comes as a surprise to most people. After all, isn't the destruction of the rainforest one of today's worst environmental disasters and surely, burning creates carbon dioxide, the cause of rising world temperatures?
Not a bit of it, according to Maggs: "For three years my trees take carbon dioxide from the atmosphere. They provide shelter for wildlife and employment for men who would otherwise be laid off. Then they are burnt to produce electricity, putting no more gas back into the atmosphere than they absorbed as they grew. The stumps regenerate and three years later they're ready for another harvest."
The key to this approach lies in the centuries-old art of coppicing which makes use of the natural ability of many trees to survive being cut down, with new withes rocketing up from an established root network - far faster than a new seedling fighting to grow both underground and above the surface. Now coppicing looks set to undergo a revival as government researchers investigate using wood to generate electricity on an industrial scale.
In theory this makes good economic and environmental sense because a tree's growth is greatest during its early years and young trees are a particularly rich source of food and shelter for wildlife. "We counted 33 species of bird in our two-year-old wood, which is more than last year," says Maggs. "But that's probably the peak; we think they drop off again in the third year." This is fortunate, as it coincides with the three- yearly harvest.
In case the concept of growing fuel to compete with oil sounds implausible, it is worth remembering that until the 18th century, Britain was fuelled by wood and charcoal. Even today, some countries still take the principle very seriously. The Swedes, for example, have 9,000 hectares of deciduous coppice and even the US is not immune: "Most people are shocked to learn Oregon gets 40 per cent of its electricity from wood," says Peter Billings of British Biogen, the trade association for wood-burning interests. "Getting the farmers to coppice is the whole reason for British Biogen," he explains. "We have to bridge the gap between an energy industry used to planning 15-20 years ahead and farmers who are more concerned about the next six months."
The Government is helping by funding half-a-dozen trial projects around the country to establish the costs and project yields. Alec Barnes, a Devon farmer, is conducting one of these near Tiverton. He says he could only afford to invest in the scheme with the help of grants.
So far, the researchers - based at the Energy Technology Support Unit (ETSU) and ADAS (formerly the Agricultural Development Advisory Service) - are two years into their studies. Although the initial results are encouraging, the scientists admit there is much to learn: "We still don't know enough about the crop," says Gareth Ellis, woodland consultant for ADAS. "We only harvested our first trial sites at the end of November. We have to experiment with the machinery and there are lots of questions to answer - whether to leave the poles whole or chip them like silage, and which machine is least harmful to the stumps left behind? Then, because it typically contains about 50 per cent water which reduces its burning efficiency, we've got to work out how to dry it down to 30 per cent."
The results are sufficiently encouraging, however, for the energy industry to be interested. Three wood-fuelled power stations are in the pipeline - to be built near Eye in Suffolk, Swindon in Wiltshire and Selby in Yorkshire. The last of these is being developed by Yorkshire Environmental, a subsidiary of Yorkshire Water: "We're applying for planning permission to build a plant," says Keith Pitcher, development manager. "Eventually we should be able to heat 16,000 homes."
The plant, which should come on line in late 1997, uses the latest gassification technology to convert wood chips into gasses by intense heat and pressure. The result is surprisingly efficient, converting 30-45 per cent of the available energy into electricity, compared with 20-25 per cent in a conventional coal plant. Many remain sceptical: "The technology is unproven," admits Ellis. "Critics say it's one step too far - an untried crop being used in untried technology."
Keith Pitcher dismisses this with a shrug: "We know from experience with wind power that prices will come down as the technology is more fully understood," he says. "We'll get an industry emerging from this and as the yields from the trees improve, returns will be better for everyone."
For all his enthusiasm, however, Pitcher has to concede he cannot compete with gas on price. The Renewable Energy Bureau estimates wood-powered electricity costs an average of 8.7p per kW, compared with 5.3p for wind power. In contrast, gas costs about 2p and coal around 3p. Underwriting Yorkshire's investment is the Non-Fossil Fuel Obligation (NFFO), a commitment placed on electricity companies to buy a percentage of their power from sustainable sources. Under NFFOs (three have been negotiated so far and a fourth is in progress), investors in new technology are guaranteed high prices for 15 years. This in turn means Pitcher can provide a long-term market to local farmers, allowing them to establish coppices while he waits for his plant to be built: "One of the reasons we are going ahead is to break the vicious cycle of no market until there's a product and no product until there's a market," he says.
Although he refuses to give details, Yorkshire is believed to be offering about pounds 20 a ton. With the research showing possible annual yields of up to 45 tons per hectare, this could be enough: "At pounds 20 a ton, farmers should be able to get about the same profit as they do on winter wheat," says Gareth Ellis.
In Devon, Alec Barnes is unconvinced: "It's not worth going into unless you can get pounds 25 a ton," he says. As a result he is looking with interest at a neighbour who is experimenting with making composite boards from coppiced wood. "As with any business, the only way you can keep prices up is to have various outlets. If you're dependent on one customer, you're at his mercy," he explains.
In the end, however, the real driving force behind wood power may lie not with relatively big plants, but on a smaller scale: "The advantage of wood energy is it is very flexible," says Dr Keith Richards, ETSU's deputy manager for Biomass Resources and Statistics. "We have several housing and industrial estates which are interested in small plants. The great thing about wood is once you have located your user, you can design the plant around them.
"Wood is only expensive if you are talking about selling the power wholesale, but if you are producing the energy on a small-scale rural site it is very competitive," agrees Peter Billings. In the end this is the attraction for Brian Maggs and Alec Barnes, who both intend to use their coppices to heat their homes and businesses: "We should make money by saving money," says Barnes.
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