Energy and trees

tree1

A tree is a plant form that occurs in many different orders and families of plants. Trees show a variety of growth forms, leaf type and shape, bark characteristics, and reproductive organs.

tree2

Trees are an important component of the natural landscape because of their prevention of erosion and the provision of a weather-sheltered ecosystem in and under their foliage. They also play an important role in producing oxygen and reducing carbon dioxide in the atmosphere, as well as moderating ground temperatures. They are also elements in landscaping and agriculture, both for their aesthetic appeal and their orchard crops (such as apples). Wood from trees is a building material, as well as a primary energy source in many developing countries. Trees also play a role in many of the world's mythologies (see trees in mythology).

Energy forestry
Energy forestry is a form of forestry in which a fast-growing species of tree or woody shrub is grown specifically to provide biomass or biofuel for heating or power generation.

The two forms of energy forestry are short rotation coppice and short rotation forestry:

* Short rotation coppice are crops of Poplar or Willow, grown for 2 to 5 years before harvest.
* Short rotation forestry are crops of Alder, Ash, Birch, Eucalyptus, Poplar, and Sycamore, grown for 8 to 20 years before harvest.

Benefits
The main advantage of using "grown fuels", as opposed to "fossil fuels" such as coal, natural gas and oil, is that while they are growing they absorb the near-equivalent in carbon dioxide (an important greenhouse gas) to that which is later released in their burning. Whereas by burning fossil fuels we are increasing atmospheric carbon unsustainably, by using carbon that was added to the earths carbon sink millions of years ago in processes which took millions of years to complete, and this is a prime cause of global warming.

According to the FAO, compared to other energy crops, wood is among the most efficient sources of bioenergy in terms of quantity of energy released by unit of carbon emitted. Another advantage of generating energy from trees, as opposed to agricultural crops, is that trees do not have to be harvested each year, the harvest can be delayed when market prices are down, and the products can fulfil a variety of end-uses.

Yields of some varieties can be as high as 12 oven dry tonnes every year.

These crops can also be used in bank stabilisation and phytoremediation.

Problems
Although in many areas of the world government funding is still required to support large scale development of energy forestry as an industry, it is seen as a valuable component of the renewable energy network and will be increasingly important in the future.

Growing trees are relatively water intensive.

The system of energy forestry has faced criticism over food vs. fuel, whereby it has become financially profitable to replace food crops with energy crops. For more information see issues relating to biofuels and Food vs fuel wikipedia pages.

 
 
     

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