Residue supply, wood

The burning process leaves very little solid remains only ash, made up of inorganic salts that rarely make up more than a few percent of the total mass of wood. When wood bums with a restricted supply of air, however, and there is insufficient oxygen to combine with all the carbon in the wood, the remains are made up of charcoal, a very porous and impure form of carbon. Charcoal is extremely stable it does not decay, nor is it altered by most microorganisms, and it may be preserved for very long periods of time charcoal often also preserves the morphology of the burned wood. Because of its stability, charcoal residues are often found in archaeological sites where wood was either used as fuel or otherwise burned. 

The fuel could be supplied at four rates. The fuel was wood residue consisting of a mixture of bark and wood. Below are some fuel data ... 

On a worldwide basis, wood constitutes an enormous, renewable raw material resource (biomass) for production of energy and chemical products. In connection with wood-processing industries large amounts of both solid residues and dissolved material remain as waste. A rational utilization of this organic waste is of utmost importance not only from the pollution point of view, but also because of the necessity of finding substitutes for products based on petroleum and other fossile raw materials, all expensive and limited in supply. 

Basic techniques for producing charcoal have not changed over the years although the equipment has. Charcoal is produced when wood is burned under conditions in which the supply of oxygen is severely limited. Carbonization is a term that aptly describes the thermal decomposition of wood for this application. Decomposition of carbon compounds takes place as the temperature rises, leading to a solid residue that is richer in carbon than the original material. Wood has a carbon content of about 50 percent, whereas charcoal of a quality suitable for general market acceptance will be analyzed as follows fixed carbon 74-81 percent, volatiles 18-23 percent, moisture 2-4 percent, and ash... 

Pellet fuel is made of wood residues which are left over from lumber production. The material is taken to a pellet mill where it is dried, compressed and formed into small, cylindrical pellets. Pellets are supplied directly to the storage device by specialised tanker trucks. 

In Austria the market for biofuels is established. Wood pellets, wood chips from forestry and sawmill residues have quite stable prices depending on supply and demand. The Price for pyrolysis oil is assumed to be the production cost calculated according (6). The price and the transport cost of the fuels used for the applications in this paper are listed in Table 3. The transport costs are calculated with a fixed and a variable con onent. The calculation is based on transportation by truck from the site of production to the site of use (storage of the biomass plant). 

For the pellet manufacture as well as the pyrolysis unit a raw material intake of 100.000 tons of dry substance wood per year is assumed. The amount is available within a transportation distance of 100 km in many places in Sweden. At present most of the wood fuel manufacturing is supplied with raw material from forest industries pulp industry, saw mills, etc. Residues and waste products may be obtained in a range of prices and only a very minor part of the potential raw material from forestry is actually collected today. 

Bioenergy is expected to become one of major energy resources for sustainable development of mankind. However, bioenergy supply potential cannot be infinite since land area available for biomass production is limited and a certain amount of biomass must be reserved for food and material. However, bioenergy can be produced not only from biocnergy plantations, which occupy land, but also from biomass residues (such as straw, animal dung, and wood scrap) which do not occupy land directly. These biomass residues are discliarged at various processes in biomass flow from harvest to consumption. 

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