Raw materials brought to pellet mills can arrive in many different forms. Some of the raw material may be sawdust, wood chips, lumber mill scrap, and even full trees unsuitable for lumber. The raw materials may be green, or freshly cut, may be partial dry or even kiln dried. By processing these raw material all in the same way, the end product has consistent moisture content, heat value, ash content, and burn characteristics.
Typically, the process starts by running the raw material through a hammer mill. These machines take sawdust and wood chips and break them down into a more consistent smaller size. Large dryer drums are then used to take out any extra moisture. After the drying is complete, the material is processed further in a mill to make an even finer material.
Next, the sawdust is pressed in a large drum with perforated rollers inside at a high pressure, and sliced at programmed intervals. This heats up and releases lignin (sap) in the wood, which binds the sawdust together into the pellet shape.
The pellets come out of the mill between 200 and 250 degrees Fahrenheit, so a cooling tower is used to bring the temperature down/harden the pellets. After cooling, they are usually stored in a large silo to await bagging. Note: Most pellet mills today are working at full capacity – so sometimes there isn’t a lot of extra time for the pellets to be in the cooling tower. So, there are small holes on the sides of the pellet bags, known as bag vents. The vents help to keep pellets with any leftover warmth from creating moisture inside the bags. If you see rows of small holes – that is perfectly normal!
The most common method for distribution in the US is to put the pellets into 40 pound plastic bags and stack them on pallets. These pallets may contain one ton (50 bags) or one and a half tons (75 bags) depending on the distribution channel.
Need to top off your supply? At this time, delivery expectations are the shortest they’ve been in months. Call 1-800-735-5387, or just order online!