Wood pellets can be made from a range of wood biomass materials. Besides wood biomass, other types of pellets (non wood pellets) can be made from paper, cardboard, grain, straw, corn husks, production waste and all manner of things. The process for making biomass wood pellets is principally the same that is used for other materials.
What is a Wood Pellet?
A wood pellet is simply biomass wood materials that have been shredded into sawdust and then highly compressed through a die cast (using hydraulic machines) to create a cylindrical pellet shape (form). The wood pellet is bound together by the naturally occurring lignin in the wood. In the UK, most Quality Woodpellets are formed in 6mm or 8mm sizes and are about a centimeter or two long.
Wood biomass used in the production of wood pellets can come from virgin trees (Woodpellets 2U currently supplies 100% virgin softwood from UK sustainable sources) or from waste materials used in industry - like sawdust (from processing) or waste off cuts for example in a furniture making factory. Before virgin or waste wood can be made into a wood pellet it is broken down into finer particles. Larger pieces of wood are first run through a chipping machine to break them down into fine particles. The finer the particle the stronger the pellet and the greater the energy it will produce.
The wood pellets are made by pressing this constituent material into a wood pellet die. A wood pellet die is a piece of cast metal that has pre-drilled pellet sized holes. Most people who buy wood pellets, purchase them in 6mm or 8mm sizes. The top of the holes are tapered like a funnel, so that as the material is pressed down into the die hole it becomes compressed as the hole becomes smaller. The vast amounts of compression used creates friction which heats the wood pellet and melts the lignin within.
Making Quality Wood Pellets
As soon as the woodpellets are extruded from the other side of the wood pellet die, they begin to cool. The lignin binding agent within the pellet begins to harden and act like glue, holding the wood pellet firmly together.
In order for a wood pellet to form properly, keep its shape and be transported to it's place of use (without breaking into sawdust), the wood biomass used to make the pellet must be dry enough to create high heat output, but still have the correct amount of moisture to retain its shape.
Generally speaking, the greater the sheen or gloss on the surface of the wood pellet, the higher quality the pellet is deemed to be. Woodpellets2U only supply premium quality pellets.