||With growing production and consumption of wood pellets the question of how to assure the pellet quality has emerged. These concerns lead to creating European standard for wood pellets in 2011 and established few years later international standard. Following these standards, the ENplus® certification was established introducing quality classes and stronger requirements for pellet production.
In North America the Pellet Fuel Institute (PFI) was established to promote energy independence through the efficient use of clean, renewable biomass fuel. The PFI offers their own quality certification program, however just like in case of ENplus® certification, pellets are tested based on variety of physical and chemical properties. Still, some pellet impurities cannot be identified this way (glass, plastic, metals, ceramics, coal, coke).
Those impurities are added to pellets unknowingly or knowingly (frauds) to increase heating value and lower moisture and ash content or used to increase weight (sand) and therefore cost per kilogram. These impurities can have very negative impact on human health and durability of stoves (increased emission of CO, CO2, and NOx, bad smell, lower the heating value and cause destruction of burners due to creation of slags).
Studies conducted at the Silesian University, using commercially available pellets, have documented a range of contaminants including plastics, coal, rust, bark grains and metal, demonstrating that optical microscopy could be an effective tool to assess the purity of wood pellets.