Pellet Boilers are the most common form of biomass boilers and use pellets which generally comprise of compacted saw dust and have a moisture content of 6 – 8%. The quality of the pellets is very important as they must be consistent in size, density and moisture content. Pellet boilers are very clean burning with very little gases emitted achieving almost complete combustion meaning they are over 90% efficient and leave very little ash. The pellets can be feed manually or a hopper is usually designed into the system so that your pellet boiler is fully automated.