How are wood pellets made ?
Choosing Hase pellet stove heating means opting for an ecological, comfortable and easy-to-use heating method . But do you know how the pellets you use for your stove are made? Discover all the manufacturing secrets of wood pellets!
What is wood pellets ?
Wood pellets, or wood pellets, are heating fuels that take the form of small cylinders a few millimeters in diameter. Discover everything you need to know about their manufacture, from the manufacturing process to the conditions to be met to be certified quality pellet .
What are wood pellets made of?
Wood pellets are made from by-products of sawmills , such as wood cuts, sawdust or wood chips.
The pellet manufacturing process allows the compaction of sawdust and shavings to make them usable for boilers and pellet stoves.
The stages of manufacturing wood pellets
The manufacturing process that transforms the raw material into pellets consists of several steps to produce quality , high-performance pellets that meet standards.
- The raw material is ground in a sawdust silo.
- The fine sawdust thus obtained is dried in a dryer drum generally fed by a biomass boiler or wood residues. The moisture content is controlled to be less than or equal to 10% after drying.
- Once dried, the sawdust is pressed in a special press to form pellets . The very strong pressure of the machine naturally ensures the cohesion of the granules, without binder or additive .
- The granules are cooled (the action of the press heats up!) and sieved to remove any dust.
- Last step: packaging! The granules are packaged in bags or in bulk , ready to use at home!
What raw material to make wood pellets?
Pellets are made from residues, shavings and sawdust from the wood industry (carpentry, flooring, pallet factory, etc.), which are agglomerated together to form small, compact cylinders 15 to 25 mm long on 8 mm in maximum diameter. They can be made from hardwood or softwood trees, or a mixture of the two. It is generally preferred to manufacture from 100% softwood trees, as this makes it possible to obtain a better calorific value, and no addition of binder or chemical additive is necessary during their manufacture.
The manufacturing process of wood pellets
The pellets are produced in large quantities, in an automated way.
To begin with, we will recover raw materials (pallets and wood residues) from specialized companies or sawmills, preferably local ones. The wood thus recovered will then be crushed in a sawdust silo, then dried in a dryer drum fed with wood via a biomass boiler.
It is only once the wood is completely dry (the humidity level must be less than 10%) that we will be able to press them at high pressure in a specific press, in order to form small dense cylinders. and consistent. No synthetic binder is added if it is softwood, because the resin itself acts as a binder. All that remains is to cool the pellets, then clean them by passing them through a sieve (to remove wood dust). They can then be packaged in 15 kg bags or one tonne pallets, or sold directly in bulk.
It should be noted that due to their compact format, the pellets do not take up much space in storage. It is estimated that approximately 1.5 m3 of space is needed to store a ton of pellets! It is for this reason that they can be produced in large quantities.
In what case do we speak of sustainable manufacturing?
So that the consumer can be informed about the pellet manufacturing process, standards and certifications have been put in place to validate their durability.
To begin with, pellet manufacturers must commit to using only 100% natural wood residues and sawdust, which have not undergone any chemical treatment, at any time in the production chain. They must also undertake to comply with the manufacturing standards set by European standard EN 14961-2, which, among other things, sets the size of the pellets.
Two main certifications have also been implemented to assess the quality of pellet manufacturing: the German DINplus certification and the European ENplus certification. These certifications guarantee that the pellets do not contain glue or other additives, that they have good calorific performance, and that their moisture content and ash content are very low (respectively less than 10% and less than 0.7 %), which guarantees optimum performance.
What is the difference between Hardwood and Softwood pellets and which one to choose?
There are several types of pellets depending on the wood from which they are made. The hardwood pellet is made from 100% hardwood (acacia, ash, oak, teak, eucalyptus, chestnut…), and the softwood pellet is made from 100% softwood (spruce, fir, larch, cedar). , pine…). There are also mixed pellets, made from 20% hardwood and 80% softwood or vice versa.
Softwood pellets are of higher quality than hardwood pellets . Indeed, no binder or chemical additive is added during the manufacture of softwood pellets, because the resin acts as a natural binder. The result is better energy performance and cleaner, more complete combustion. This is why the Enplus and Dinplus certifications are awarded only to 100% resinous pellets.
To guide consumers in their purchase of wood pellets, certifications have been put in place to guarantee the quality of the pellets: the German standard Dinplus, the European standard ENplus, and the French standard NF biofuels.These certifications meet the European standard EN 14 961-2 (EN ISO 17 225-2 internationally) concerning the manufacturing process of pellets: they thus make it possible to guarantee that the pellet meets the criteria ensuring a quality of optimal combustion. Among these criteria, we find in particular the humidity rate, which must be less than 10%, the ash rate, which must be less than 0.7%, or the calorific value (PCI), greater than 4.6 kWh/kg.
Why buy certified pellets?
To guarantee the quality of the pellet and therefore its energy performance, certifications have been put in place, in particular the European standard ENplus and the German standard DINplus. Buying certified pellets will thus guarantee you the purchase of a 100% resinous and 100% natural pellet, without the addition of additives or chemical binders, and therefore not harmful. In addition, by buying certified pellets, you ensure the optimal performance of your pellet heating system, with pellets whose moisture content does not exceed 10% and whose ash content is less than 0.7%. Buying certified pellets therefore means spending more on purchase to make greater savings in use!
How to choose the right wood pellets for your stove?
Now you know everything about making pellets for your Hase pellet stove ! You just have to be careful to choose the right pellets .
The quality of the pellets has a considerable influence on the cleaning and maintenance cycles. We recommend pellets with an ash content of 0.25%, a bulk density of 650 kg/m³ and a calorific value Hu > 4.9 kWh/kg.
The ideal size for pellets is 6 to 8mm in diameter and a maximum of 30mm in length. This size allows the correct feeding of the stove and avoids possible blockages .
Finally, be sure to only use pellets that meet the ENplus-A1, DIN PLUS, Ö-Norm 7135 or DIN 51731 standards and have an ash content of < 0.7%, which are the only ones that guarantee optimal performance of your pellet stove. Ask your pellet supplier for the ash content. The weaker it is, the better.