What the specification fixes
It is the part of the solid biofuels series that deals with graded wood pellets for non-industrial use — the sack a householder buys. It names the properties a pellet is classified on and sets the classes each falls into.
The properties are physical and chemical rather than commercial: the raw material the pellet may be made from, its dimensions, its moisture, its ash content, its mechanical durability, the proportion of fines, its energy content, and the presence of certain elements. A grade is a combination of classes across all of them, which is why a single letter on a sack carries so much.
It is a specification, not a certificate. It says what a grade consists of; it does not check that a particular pallet complies.
What it does not promise
It does not promise the sack in front of you meets what it claims. That is the job of a certification scheme, and the schemes exist precisely because a specification alone is unenforceable.
It does not promise the pellet suits your appliance. An appliance is tested on a defined grade and its manufacturer states what it accepts; feeding it something else puts it outside the conditions its own figures were taken under.
And it says nothing about storage. A graded pellet that has sat in a damp garage is no longer the thing the grade described, because moisture is one of the classified properties and it is the one that changes after the sack is filled.
The documents that sit beside it
The two certification schemes a buyer meets on the front of a sack are built on this specification and add the thing it cannot do: verification. One is run by a European pellet industry body and covers the chain from production to delivery; the other is a certification mark operated by a German certification body.
The appliance standard for pellet appliances references the fuel specification rather than restating it, which is what ties the two together: the appliance’s published figures are figures on a stated grade.
Where it appears on this site
On the pellet family, on the pellet appliances, and on the igniter — because the property that decides how often a burn pot needs scraping is the ash content, which is one of the classified properties rather than a matter of brand.
Where a listing prints a grade, the page prints it. Where a listing prints only a scheme name, the page says which scheme and what it verifies. Where a listing prints neither, the page records that, which for a fuel is a more serious silence than for a piece of metal.
Questions that keep arriving by post
What does the ash class actually change for me?
How often you clean. Ash content decides how quickly the burn pot fouls and the pan fills, and on an appliance that runs for hours unattended that is the difference between weekly attention and daily attention. It is a classified property, not a brand attribute.
Are fines just dust I can ignore?
They are a classified property because they matter to the feed. A high proportion of fines changes how the auger delivers and how the burn pot behaves, and it is one of the things a certification scheme checks at delivery rather than only at production.
Does a higher grade pellet give more heat?
Energy content is one of the classified properties, so the grade does carry it. But the property owners notice first is ash, not energy: the difference in heat between grades is modest, and the difference in cleaning is not.
Last reviewed 22 September 2026