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Modern society is becoming increasingly energy intensive, with European energy consumption increasing by1 - 2% every year.There has been much discussion in the political arena about the impact of fossil fuel consumption andconsequential carbon dioxide emission levels.Human activities have contributed to theconcentrations of greenhouse gasses in theatmosphere together with those from natural

sources such as volcanic activity and decayingvegetation.The build up of carbon dioxide and othergreenhouse gasses trap some of the Suns energyresulting in a warming of the earths surface.This is known as the Greenhouse Effect. Theconsequences of Climate Change have been thesubject of much speculation in varying degrees.

The UK is responsible for the release of around3% of global CO2 emissions caused by man,despite having only 1% of world population.International and National targets are now inplace to reduce carbon dioxide emissions byreducing dependence on finite supplies of fossil

fuels.One key element is to maximise the use ofrenewable energy sources.Other drivers for reducing reliance on fossil fuelsinclude:

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Costs:Energy charges are almost certain to rise as it becomes politic to include the environmental costs of energygeneration in prices paid by consumers.

Security of Supply:The UK can no longer meet its total energy demand from indigenous sources. Whilst coal reserves are still

potentially available, oil and gas are increasingly sourced from politically and economically unstable areas ofthe world.There are five basic categories of biomass material:

Virgin wood, from forestry, arboriculture activities or from wood processing.

Energy crops: high yield crops grown specifically for energy applications.

Agricultural residues: residues from agriculture harvesting or processing.

Food waste, from food and drink manufacture, preparation and processing, and post-consumer waste.

Industrial waste and co-products from manufacturing and industrial processes.From here onwards we will only discuss wood as a biomass heating fuel.

Wood boilers have a proven history of reliability. Other biomass heating fuels such as grain etc are reportingheavy degradation to boilers. This is due to the high levels of certain chemicals such as chlorine whichdestroy steel and stainless steel boiler surfacesWood combustion is CO2-neutral, only as much CO2 as the plant accepts during the growth can be liberatedat the combustion.Fossil energy sources liberate during the combustion additional CO2 that cant be taken up over a shortperiodWood combustion is CO2-neutral, only as much CO2 as the plant accepts during the growth can be liberatedat the combustion.Fossil energy sources liberate during the combustion additional CO2 that cant be taken up over a shortperiod.Growing 1 m of wood = 1 Tonne of CO2 is taken out of the atmosphere.

The most common fuel for domestic biomass heating systems is woody biomass from local forestry andforestry residues or energy crops such as willow coppice. Forestry residues or waste or by-products such as

from sawmills and other woodprocesses, can also be used, subjectto quality.

The most common and convenientforms of woody biomass for domesticheating are

Wood chips,

Wood pellets

Split logs.

Contrary to popular opinion, all woodspecies have a similar calorific valueper unit weight provided the moisturecontent is the same but due to thediffering densities they have adifferent calorific value per unit of volume and thus the amount of fuel storage required. The energy outputfrom a single firing when using a log boiler varies from species to species.

They key difference is moisture content when felled (high in alder, low in ash).

Traditional logs are still widely used for heating. Logs are generally suitable only for manually fed appliances

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and due to the longer period of seasoning they require a greater area for storage.

Different species of wood burn slightly differently which is significant in purchasing decisions. All woods burnbetter when well seasoned and all burn better when split.