Compressed, cylinder-shaped pieces of residual wood with a diameter of 6 mm and a length of 2 to 4 cm. These little "bundles of energy" have a high energy content and inherent density, an excellent calorific value and their combustion is environmentally friendly. The ash produced is works very well as a valuable garden fertiliser.
Pellet is an English word meaning "small, rounded, compressed mass of a substance". The old French term "pelote" means "ball" and, in Latin, "pila" means "bundle" or "pile".
Of pure, natural, dry saw and machining dust, with no chemical additives. Preferably spruce, although with a small percentage of larch and pine wood as well. Small amounts (1 to 2 percent) of exclusively biogenic raw materials, such as corn starch or corn flour, may be added as compression additives.
Wood shavings are dried and, if necessary, chopped into even smaller pieces. Then the shavings are pressed through a matrix. Finally, the pellets are cooled, sieved and stored in a silo.
Premium pellets for private households must comply with standards ENplus and ÖNORM M 7135. The most important parameters of ÖNORM M 7135:
• Diameter: 6 mm
• Length: 30 to 40 mm (max. 1 percent up to 45 mm)
• Surface: smooth
• Density: min. 1.12 kg/dm³
• Bulk weight: min. 600 kg/m³
• Energy content: min. 4.6 kWh/kg
• Water content: max. 10%
• Ash content: max. 0.7%
• Fines content (before transport): max. 1%
• Binding agents: prohibited
• Impurities: none
Since 2010, new EU standard EN 14961-2 stipulates three common pan-European quality classes for pellets:
• Class A1 corresponds to that of the current ÖNORM
• Class A2 may have a slightly higher ash content (up to 1.5 percent)
Class B is used in the commercial and industrial sector and can have an even higher bark content as well as an ash content of up to three percent. Wood is the only permitted raw material for all three quality classes. This standard is the basis for the ENplus seal of approval, the new quality certification for pellets in the top segment.
© ÖkoFEN 2012