Pellets – The Fuel

Basic facts about fuel pellets
A fuel pellet is as per definition a "short cylindrical piece of wood" intended for combustion. Fuel pellets are produced by pressing a finely powdered dry fuel from waste products typically derived from the forest industry. The diameter of the fuel pellets within the European Union today varies between 6-8 mm, with a standard length in the range 5 mm to 30 mm.
The overall effect on the environment using pellets is very low when burning pellets. Combustion is typically carried out in a pellet fired system such as for example a pellet boiler or stove. Upon combustion the stored sun energy inside the raw material is then released. The emissions of unburned hydrocarbons as well as dust are in most cases way under the limited values of most local authorities throughout the EU. The carbon dioxide which has been required during the growth cycle of the tree is then released again in the wood pellet burning process to once again be taken up by nature. In other words, this is a balanced circuit. The combustion of wood pellets does not bring additional carbon dioxide to the atmosphere, which is the case when combusting fossil fuels such as oil, gas and/or coal.
Pellets can be transported on a large-scale via bulk loaded lorries for example, either for domestic use or for use in district heating plants close to a harbor, where transportation from the boat already exists. For distribution to home-owners there are also developed alternatives such as pellets in bags (typically in 10-15kg bags), on pallets, bigger bags or bulk loads for example.
The amount of energy used for transportation, drying and pelletizing is approximately six percent of the total energy content of the raw-material, provided that the raw-material is a dry by-product from the wood industry. The actual transportation of the pellets typically accounts for less than one percent of the total energy content of the fuel (at distances under 100 km). Therefore you can produce 18 times back the energy that you have put into the process. If the raw-material has to be dried the relationship is then approximately 1:7.
Within Sweden the Pellet Industry's National Federation (PiR) has 16 member companies spread out throughout Sweden. Together they own 23 out of 25 of the total largest pellet production plants there are in the country and account for approximately 85% of the total pellet production on the Swedish market.
Some more interesting facts about wood pellet fuel
1) The compactness of the wood pellet material comes from the lignin which is contained in the wood itself, and allows the production of pellets without the use of glues or binders.
2) Good quality pellets have a density which varies between 600 kg/m3 and 750 kg/m3, with a moisture content which varies from 5% to 8% by weight.
3) Pellets also have technical advantages. While good-quality timber has a typical calorific power of 4.4 kW/kg (with 15% moisture, i.e: after about 18 months' seasoning), the equivalent figure for pellets is 4.9 kW/kg.
5) To ensure they burn well, the pellets must be stored in an area that is free of humidity and protected from dirt.
6) The poorer the quality of the fuel, the less well it will burn and the more frequently you will need to clean the internal parts, such as the grate and the combustion chamber.
7) The main certifications of quality for pellets in the European market are DINplus and Ö-Norm M7135; these ensure the following qualities:
• Calorific power: 4.9 kW/kg
• Water content: max 10% of weight
• Percentage of ashes: max 0.5% of weight
• Diameter: 5 to 8 mm • Length: max 30mm
• Contents: 100% untreated wood, with no added bonding substances (bark percentage 5% max). We strongly recommend using certified fuel in pellet stoves to European standards (DINplus and Ö-Norm M7135).
8) If you use fuel of inferior quality, or not conforming to the specification given above, it compromises the running of your stove and can lead to the termination of the guarantee and of the manufacturer's responsibility for the product.
9) Recently the supply of pellets from distributors has become very good throughout Europe. The number of manufacturers & distributors coming on line is increasing all the time. This will hopefully mean the price of pellets will get cheaper, become more competitive and they will be more readily available.

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