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Biomass and Coppicing

For Cheap, Renewable Energy.

Biomass is a biofuel derived from plants (traditionally young plants) which are harvested and suitably processed for burning. The heat produced is the form of energy which can be harnessed. Other names commonly associated with the technique are Coppicing and Energy Fuel. Biomass is, strictly, a form of biofuel but when we talk about biofuels normally we have in mind biodiesel or ethanol and methanol which are mainly (but not exclusively) applicable to motor vehicles.

The concept becomes attractive only when the plants are replaced at a rate equal to the rate at which they are harvested. It is argued that the carbon sinking effect of the growing plants neutralises the carbon emitted when the the fuel is burnt. Young trees are better sinks than mature trees. Since, by definition, the extraction of energy is accompanied by the release of carbon, it is not such an ideal solution as the generation of solar or wind power, for example. Nevertheless, it provides a renewable source which can be called on no matter what the prevailing weather conditions are and is much more eco-friendly than burning fossil fuels such as coal and oil. Additionally, in the right circumstances, it can be a cheap option.

Coppiced Area Showing Rapid Regrowth

Recently Coppiced Area Showing Rapid Regrowth: Click to Enlarge

  Biomass methods are basically low tech and they are particularly useful where there is surplus low-grade arable land. Therefore the system is appropriate, not only for some undeveloped countries, but also for the UK and other parts of Europe where efficient agricultural techniques frequently lead to over production of food crops. The potential is attractive because it is relatively cheap (eg compared to the radical solar, wind, etc schemes) and could take advantage of the infamous subsidies currently provided simply to get farmers to do nothing with their land. Although the processing requires the input of energy (cutting, chipping, pelleting, transporting etc) it can be quite efficient and especially with a system of CHP, q.v. Where the location is suitable, for example in rural areas, end-users may have access to logs at negligible expense and others may be able to extract clean (ie untreated) timber from constructors' waste which otherwise may go into landfill.
If this process was developed fully in the UK, according to the DTI, it could become a major agricultural industry and would be capable of meeting a significant proportion of the current electrical demands. One of the most practical way of generating biofuels is to plant fast-growing trees, such as willow, and cut them back every few years, allowing further growth to occur. This is usually referred to as coppicing and the fuel is solid wood, often chipped or pelleted. Such fuels have the advantage that they are easily and cheaply storable for use as required. Another method is to grow suitable green plants from which liquid vegetable oil can be extracted. These methods can have the disadvantage of occupying land that could be otherwise used, e.g. for food crops, however by sensible management such clashes can be avoided.

Biomass implementation is not without its opponents. Apart from the underlying disadvantages that carbon is emitted and there may be toxic products of combustion, some feel that the countryside would be spoiled by the sight of disfigured forests, and there are other legitimate objections such as the hogging of arable land, as mentioned above, and a reduction in biodiversity.

On the other hand the prospect of a new, significant, cleanish, renewable energy source which is cost effective and which will provide employment is likely to appeal to government and farmers alike. Pelleted wood burners are likely to increase in use in the UK because the fuel should be reliably available and in areas where oil and electricity are the norm the capital outlay can be offset in a few years. In summary biomass has the potential to contribute to carbon reduction, convenience and possibly economic development.

For a more detailed discourse on this and related topics visit the web-site of the Network for Alternative Technology and Technology Assessment. NATTA publishes Renew, a bimonthly newsletter.
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By Gordon Shaw

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Originated: December 2000,  Last Amended : 28 October, 2013