Wood has been burned by mankind since first we harnessed fire. It has been the fuel behind the provision of heat, cooking, defence and craft to name but a few things. Nowadays, when we are quickly watching our fossil fuel reserves dwindle away, we are seeking 'a great and sustainable resource'. Well, we need look no further than wood to provide a significant alternative; Wood for fuel, that old chestnut. Before I explain the argument behind the use of wood, let me just explain my background in this subject. I work for an organisation in the Highlands of Scotland, which, for the past four years has been managing a project which has aimed to promote the development of woodfuel supply chains, utilising the vast timber resource in Scotland.
Fossil fuels, such as coal, oil and gas have been the back bone of our energy supply since the dawn of the industrial revolution. The "Black Gold" and its two cohorts have also been responsible (according the the majority of informed opinions)for the increased pressure on our planet. Why? Carbon Dioxide. The main cause of the negative impact on the environment from the use of fossil fuels is the subsequent release of carbon dioxide. The production of fossil fuels takes millions of years worth of heat and pressure applied to fossilised remains of organic material (including plant and animal). It is non-renewable i.e. we are depleting the resource before it has time to replace what has been removed. Like it's name, fossil fuel, the carbon which is released when it is burned is also ancient. This means that when the fuel is burned, this "fossilised" carbon dioxide is released back into the atmosphere. This addition of this carbon dioxide overloads the atmosphere and causes Global Warming, via the infamous Greenhouse effect. This is an important fact in the argument for the use of woodfuel.
How is burning woodfuel different to burning fossil fuels? Simple, it is, if managed properly, a "carbon neutral" fuel source. What does carbon neutral mean? Well, if we go back to our fossil fuel for an example; I mentioned that fossil fuels are not renewable. They cannot be replaced as quickly as we use them. In addition to this fact, when they are burned, fossil fuels release ancient carbon dioxide back into the atmosphere, which contributes heavily to Global Warming. The reason why it contributes so heavily to Global Warming is because the carbon cannot be removed and as such the atmosphere becomes over-loaded with it. Woodfuel offers a real alternative to this by being "carbon neutral". The Carbon dioxide emitted from wood when it is burned does escape into our atmosphere, that much is granted. However, unlike fossil carbon, this carbon dioxide can be reabsorbed by more plantations of trees as they grow. This means that provided plantations of wood resources designated for woodfuel use are replaced and managed as they are utilised, there will always be more new and growing trees to absorb the carbon dioxide released as it is burned, therefore offsetting the carbon balance. The carbon dioxide released by burning wood is therefore re-entering the carbon cycle and not being added into our atmosphere like when fossil fuels are burned.
The use of woodfuel cannot provide the energy to the same extent that fossil fuels do, especially considering that over 80% of our global man produced energy comes from burning fossil fuels. However it can be utilised to provide a very real and sustainable alternative to many areas of the world. Let me explain using the Highlands of Scotland as an example.
In the Highlands of Scotland there is a vast resource of mature woodlands. Mostly plantations of pine and conifer species. These woodlands do not have a strong market value, and as such it does not make financial sense for a forestry contractor to harvest them. As such, this huge resource is not being utilised. If the woodfuel market became better established and stronger in Scotland, this resource would have a market and would therefore be harvested. Once this is harvested the wood can be either used as one of three sources of fuel. It can be chopped into logs and burned in log burning stoves; it can be chipped and dried and then burned in chip burning boilers; or it may be chipped, dried then turned into sawdust before being forced under extreme pressure into a wood pellet. I will explain the benefits of each of these alternative fuel sources individually.
The image of a log burning on a fire is enough to make me turn to jelly with relaxation. It's beautiful, cosy and environmentally sound. The burning of logs can be very "carbon neutral" indeed. If you harvest it yourself and do not transport it using a vehicle (which burns fossil fuels and emits carbon dioxide into the environment), then the only carbon released into the environment is offset by that which is absorbed by the growing trees. If you are chopping the tree with nothing but an Axe and sweat then you can sit back and bask in the warm glow of your log fire coupled with a sense of environmental well-being! However, you may want to use a chainsaw, and that burns fossil fuel (so it's not completely carbon neutral).
Woodchips are now used widely throughout much of northern Europe and central Europe. They are also being used by several large installations in Scotland and the remainder of the U.K. So what is a woodchip? Well, once the stem of the tree has been harvested, it is sent through a multi-bladed chipping machine which, you guessed it, chips the stem into small pieces of wood. These chips are then dried so that their moisture content is between 15% and 30% (larger boilers can happily burn chips with a larger moisture content, perhaps as high as 50%). This reduced moisture content means the boiler will burn the chips with greater efficiency and release larger amounts of energy. A chip boiler can vary in size and can even be so large as to heat a district. In Finland there are many wood chip fueled boilers which can provide heating and hot water for hundreds of homes. The carbon dioxide released by the burning of wood chips is also very environmentally friendly, with the carbon dioxide released from the burning being offset by that which the tree plantations absorb. However, the carbon dioxide released by through the harvesting, transport, chipping, drying and further transport of the chips does add an impact on the environment - though it should be noted that this is no where near as bad as that of the carbon balance of fossil fuels.
3) Wood Pellets
Wood Pellets are the most efficient of all the types of wood fuel. They are produced through a technical process which applies huge amounts of pressure to sawdust, eventually forcing it into a small pellet shape, much like calf pellets used in agriculture. These pellets can be burned, much like wood chip, in a small domestic sized boiler or in a larger boiler, capable of heating many homes. The benefit of the pellet comes from its burning efficiency (approximately 97% efficiency), its small size (a small amount will produce a lot of energy, with perhaps a dozen producing enough energy to boil enough water for a cup of tea), and in addition to these two facts pellet boilers require minimal maintenance. As it burns so efficiently it will produce virtually no ash. Again, like the chips, the pellets will release carbon dioxide which is then offset by that absorbed by trees, however the stages involved in its production may release some additional carbon balance.
With these three examples of wood fuel explained, I think it is fair to say that wood can be utilised to provide us with clean and green energy. It will not be the sole replacement for fossil fuels, but combined with other renewable and sustainable fuel resources, it will certainly go a long way to doing this. In Scotland we are now seeing a huge increase in interest towards woodfuel. With some hard work and greater education, the huge timber resource can hopefully be utilised as an alternative form of energy.