| With the rising costs of heating solutions based on | | | | is instantly compressed as it moves through the |
| fossil fuels, wood pellet stoves have been growing | | | | holes in the die; the process also causes the wood |
| more and more popular. Not only do they allow a | | | | pulp to heat up significantly. This heat is vital to |
| cheaper alternative to gas or oil-based heating | | | | the pellet-making process, as it not only helps to |
| solutions, but they also allow a means for | | | | remove any excess water that might have been |
| sawdust and other leftover wood products to be | | | | in the wood pulp but it also causes the lignin |
| put to a good use. Though the pellets which these | | | | contained within the cell walls of the wood to be |
| stoves use may be made of a number of | | | | released and form into a natural plastic-like glue |
| different materials, in most cases they still are | | | | that holds the pellet together without the need |
| made from some form of wood that has been | | | | for any additives or additional materials. |
| tightly compressed in order to keep them | | | | Standards to Which Pellets Conform |
| compact while still letting them burn easily. | | | | Though there may be some very slight |
| The process by which wood pellets are made is | | | | differences between pellets formed from one |
| relatively simple, regardless of the type of | | | | type of wood when compared to those from |
| materials that are used to make them. There are | | | | another wood, there are still some basic |
| some basic standards to which the pellets should | | | | standards to which most if not all stove pellets will |
| conform when the manufacturing process is | | | | conform. The standards most commonly used |
| finished, of course, though these standards are | | | | require pellets to have less than 10% of their |
| generally easy to meet regardless of the material | | | | total mass as water, to have a density larger |
| used to make them. Some materials are | | | | than 1 ton per cubic meter (which is dense |
| unsuitable for use in stove pellets, largely because | | | | enough that they won't float when placed in |
| they could present a danger to pellet stove users | | | | water), and that they are structurally sound |
| when burned. | | | | enough that they won't easily crush or fall apart. |
| Preparing the Wood | | | | Additionally the pellets should contain a low dust |
| Before sawdust and other scrap wood can be | | | | and ash content so that they will burn cleanly. |
| made into pellets, it must first be processed and | | | | These standards are generally easy to meet |
| pulped. This is generally done by putting the wood | | | | regardless of the type of wood used, since the |
| through a hammer mill, a device which spins the | | | | hammer mill pulps the wood to the point that it is |
| wood material at high speeds while it is impacted | | | | just broken down wood fiber (which generally has |
| repeatedly with pivoting hammers. This repeated | | | | the same qualities for all types of wood.) |
| pounding will pulverize the wood in the mill, | | | | Materials Which Can't Be Used |
| reducing it to a dough-like mass with a uniform | | | | Because of health and safety concerns, there are |
| consistency. It's only when the wood has been | | | | some materials which cannot be used in the |
| pulped to this degree that it can be formed into | | | | manufacture of pellets. Any wood products which |
| pellets for use in pellet stoves. | | | | have been coated with melamine, painted, or |
| Forming the Pellets | | | | otherwise treated can't be used because they can |
| Once the wood "dough" has been made in the | | | | release harmful fumes when they are burned. |
| hammer mill, it's time to form the wood into | | | | Likewise, recycled materials such as particle board |
| pellets for use in stoves. The wood pulp is placed | | | | are unsuitable because of the chemicals which are |
| into a press which injects it under high pressure | | | | generally used in the recycling and reforming |
| through a die that has holes from 6mm to 8mm | | | | process. The wood must also be free of |
| or larger in it (depending on the size of the pellet | | | | contaminants or any artificial additives, since these |
| that the manufacturer is wanting to make.) The | | | | additives and impurities can also cause the release |
| wood pulp is under a high enough pressure that it | | | | of dangerous chemicals while burning. |