Wood Pellets are made from compressed sawdust with little or no additives. They are typically sold in 40 pound bags and one-ton pallets, which are comprised of 50 bags.
Pellets are made from both softwoods and hardwoods, however since they are both highly compressed, the heat value from all types is similar. A Heat Value of 8500 BTU per pound is average.
Pellets for residential use are 1/4" thick and from 1/2" to 1" in length.
Pellets are graded according to the ash content - if they contain less than .5% ash they are Premium Pellets, while higher ash contents are classified as Standard. Pellet with extremely high ash content as classified as Industrial and are not suitable for use in residential pellet equipment.
The raw material for Wood Pellets is usually waste sawdust and chips from sawmills and wood fabrication companies.
Here is a list of N. American Pellet Plants