Growing willow for energy is nothing new for the UK – it’s has been done for very nearly the last 40 years – but with today’s mounting interest in both energy saving and renewable energy, the idea is becoming increasingly popular.
While the whole issue of growing energy crops instead of food has been heavily criticised of late, unlike approaches which divert edible materials to biofuel production, growing willow coppices doesn’t take the food from anyone’s table.
In addition, since the economics of the whole thing works best when the wood produced is burnt relatively close to where it was grown, coppiced willow helps reduce “energy miles” – and an energy saving in transport means better energy efficiency overall.
It’s not really something that’s likely to work in the average back garden – although you can certainly do it for a bit of fun – but on a larger scale and particularly for rural communities, it can be a worthwhile option to consider.
How Does It Work?
Willow “whips” – long, thin cuttings taken when the trees are dormant, during winter – are planted in the spring, in long rows to make eventual harvesting easier. Apart from needing the ground around them to be weeded to keep down competition until they become established, willows are a fairly undemanding crop to grow and thrive in the British climate.
In many places, they will put on around 6ft (1.8m) of growth a year, which means that by the time they are ready for harvest – after three years – the whips will have become sizeable trees.
Harvesting takes place in the winter, normally using a converted sugar-cane harvester, which travels along the rows, cutting the willows at the base and dicing the wood into 4 inch (10cm) “billets” which are then stored and allowed to air dry.
Once dry, the wood can be delivered for use – normally for local heating schemes, although in 2004 the huge Drax power station near Selby began using willow material alongside coal to generate electricity and number of other large power stations have also done so since then.
Energy Saving and Energy Efficiency
For large premises, especially farms, local schools of nursing homes, willow can be an ideal heating solution, especially since it can be grown either on site, or very close by, which makes a great deal of sense from the perspective of both energy saving and carbon reduction.
Compared with the transport cost of coal or oil to relatively remote areas, where gas is not available, the straightforward economic part of the energy saving is obvious, while additionally, there is also the saving in diesel – another fossil fuel – to consider. With much reduced delivery distances, locally grown willow clearly scores highly in the sustainability stakes.
Burning willow requires a specialised type of boiler, with an automatic feeder and associated controls to ensure everything keeps working at its best – and these do not come cheap. However, the systems themselves normally have a very long lifespan – often as much as 30 years – and if properly serviced seem remarkably robust in operation.
Aside of the design of the boiler itself, the main influence on overall energy efficiency tends to be the heat distribution system – responsible for moving the heat around to where it’s needed – and the levels of insulation in the buildings themselves.
However, making sure that lofts, walls and pipes are properly insulated is a major part of any energy saving project – so using willow doesn’t make much in the way of extra demands in that respect.
Carbon Neutral, Renewable Energy
Technically known as “Short Rotation Coppicing” – often abbreviated to SRC – this form of energy production is sustainable and carbon neutral, which accounts for much of its appeal. After harvesting, the trees once again begin growing from the root which remains in the soil, providing a new energy crop every three or four years, for around 30 years or more of useful life.
Since when the trees are burnt, they only release the carbon they took up when they were growing – rather than the “pre-historic” carbon released by fossil fuels – they don’t make a net contribution to the atmosphere and hence the claim to carbon neutrality.
A growing number of farmers have started producing willows, so in addition to providing energy, there are benefits to the rural economy and employment, while the coppiced woodland makes a valuable habitat for birds, mammals and other forms of wildlife.
Although this form of renewable energy isn’t always going to be the most appropriate, it can be a very effective alternative way of heating fairly large buildings and if nothing else, it gives a whole new meaning to the expression “grow your own”!