Coppicing: How it worksThe project for farmers in the south-east is a prerequisite for establishing a viable biomass industry, writes Iva Pocock
A pilot scheme sponsored by the Forest Service has been welcomed as a positive step in promoting renewable energy crops.
Under the scheme farmers in the south-east are being paid a premium rate to grow short rotation coppiced (SRC) willow.
The Irish Bioenergy Association (IrBEA), which promotes the production of renewable energy from plant sources called biomass, said the scheme is a prerequisite for establishing a viable biomass industry in Ireland.
Clearpower, a renewable energy company, forestry consultants Purser Tarleton Russell and a Wicklow farmer initially approached the Forest Service in 1999, having completed a feasibility study funded by Barrow Nore Suir Leader, on the viability of SRC willow as an energy source.
The scheme was officially approved in 2001 and is presently funding 50 hectares of willow for five years. Four farmers in Wicklow, Kildare and Kilkenny are participating to date.
"We've one two year old crop and it's going very well," said forester Mr Paddy Purser. "But after 50 hectares we don't know. We are pressing the Forest Service to take further leadership in this area."
The Clearpower Energy Crop Scheme promoters are interested in the energy value of the crop and are exploring its use for powering Combined Heat and Energy (CHP) plants and as a raw material for energy pellets.
"The CHP would be fuelled by willow and sawmill residue and the heat from it used to dry raw willow, reducing its volume by 50 per cent," said Mr Simon Dick, director of Clearpower.
"Once the willow is dried it is then milled and compressed under intense heat and pressure to produce a hard pellet, which can be used as a fuel,", he added.
CHP plants produce both heat, which can be used for district heating systems, and electricity. The advantage of fuelling CHP plants with biomass such as willow is that it is a carbon neutral energy source.
"The crop fixes carbon dioxide from the atmosphere as it grows and then releases it when it is converted into energy," explained Mr Dick.
"Crops such as this can replace the combustion of oil, peat and other fossil fuels, reducing harmful greenhouse gas emissions while also providing sustainable incomes to rural communities," he said.
Fuel pellets produced from SRC willow are hugely popular as a domestic fuel supply in Scandinavia, said Mr Dick. He claimed that 40,000 pellet stoves have been sold there.
He also said that in Austria substantial grants are available to house builders wishing to install pellet stoves and that pellets are being imported because of a shortfall in local supply.
In Ireland, the promotion of biomass projects such as the Clearpower Energy Crop Scheme has suffered a setback following announcement of the new Alternative Energy Requirement (AER) programme, despite current support from the Forest Service. The new price offered for electricity produced from bioenergy is "probably unrealistic for attracting people to generate from biomass such as SRC," said Mr Malcolm Dawson, president of the Irish Bioenergy Association.
"The price being offered is significantly below that being offered to similar willow-fired stations in the UK," said Mr Dick. Although there are a number of planned small scale biomass projects he reckons none will go ahead because of the poor prices offered under the AER programme. By small scale he means power plants producing less than 10 megawatts of electricity, enough to supply the electricity demands of 18,000 homes. Mr James Kennedy of Natural Power Supply Ltd, which is interested in growing SRC willow, said he recently visited the UK and "power plants are out there looking for people to grow SRC willow" because of the incentives.
Coppicing is a woodland management technique traditionally used for producing firewood and small dimension timber for building, fencing and basket making. The practice had died out, but is now being resurrected in the search for sustainable energy sources.
Oak, willow, hazel, birch and sweet chestnut were the most popular coppicing species but currents efforts at using coppicing to produce industrial scale biomass as an energy supply are focused on willow.
Coppicing depends on the species' ability to grow multiple new shoots from a single stem after it is cut back to ground level. When cut, each plant develops a "rootstock" that feeds new shoots.
To establish a crop of short rotation coppiced (SRC) willow, year old single-stemmed trees are cut back in the winter, ensuring four or five shoots the following spring. Once established, the coppiced wood is left for three years before harvesting, usually in the winter when the leaves and sap are down. Thereafter it is harvested on a three year rotation, with yield increasing over the first three or four cycles.
SRC willow is planted in rows at high density with approximately 15,000 trees per hectare. The average annual yield from a hectare of SRC is 10 tonnes of dried wood.