Oak pellets

Oak as a raw material

Oaks are a group of broadleaved species — in Central Europe these include pedunculate oak, sessile oak and Turkey oak. Oak wood is a valued material in joinery and furniture-making, and the by-products of its processing — sawdust, shavings and offcuts — can be used for pellet production. If they have not been chemically treated, they belong to the raw-material group allowed in class ENplus A1^[1].

As with any species, “oak” is a commercial term — the species is not a mandatory marking on an ENplus bag^[2]. Pellets sold as oak may in practice be a blend in which oak predominates; it is worth asking. More on blends in the article on mixed wood pellets.

What we know — and what we do not

The sources this site relies on contain no measurements of ash, calorific value or ash melting temperature made specifically for oak wood. This is why we do not give “figures for oak”. We can, however, rely on the typical values for hardwood as a group:

In addition, the Finnish VTT studies lead to the general conclusion that hardwood species contain more ash than softwoods^[44]. For oak pellets, this means one thing above all: the cleanliness of the raw material is key, especially the bark content — hardwood bark can contain as much as 10% ash^[45]. The A1 limit is 0.70% on a dry basis^[1].

Does hard wood make better pellets?

This is one of the most common assumptions. Oak wood is hard and heavy, so intuition suggests that the pellets will also be harder, denser and “go further”. The reality is more complex. In pellet production, the wood is first milled into a meal and then compacted in the die. The density and strength of the finished pellet therefore depend to a large extent on the moisture content of the raw material, its particle size, the press settings and cooling — we cover this in the article on pellet hardness.

The parameters that describe these characteristics in measurable terms are mechanical durability (The resistance of pellets to crumbling and abrasion, determined according to ISO 17831-1. Result: the proportion of the mass that remains in pellet form after the test.)The resistance of pellets to crumbling and abrasion, determined according to ISO 17831-1. Result: the proportion of the mass that remains in pellet form after the test. (ISO 17831-1)^[18], particle density (The mass of individual pellets relative to their volume, determined according to ISO 18847. ENplus requires the value to be stated, with no limit.)The mass of individual pellets relative to their volume, determined according to ISO 18847. ENplus requires the value to be stated, with no limit. (ISO 18847)^[27] and bulk density. ENplus requires a durability of at least 98.0% in class A1 and a bulk density of 600–750 kg/m³, while particle density only has to be stated^[1]. None of these parameters is tied to the species — oak does not guarantee them in advanceData require verification: The site’s sources include no comparative studies of the durability and density of pellets made from different species..

Where oak wood comes from

Oaks are particularly important in Hungary: they cover approx. 32.7% of the forested area, including Turkey oak at approx. 11.7% (editorial calculation from data in hectares)^[53]. In Slovakia, oaks cover 10.2% of forests^[50], in Germany 12%^[57], and in Lithuania they account for approx. 3% of the growing stock^[56]. Ukraine’s forestry agency lists oak among the country’s dominant species^[59]; we have not been able to confirm the percentage shares of individual species in Ukraine in an official sourceData require verification: Percentage shares of tree species in Ukraine are not given in the official source — the data require verification in the primary source..

More on individual countries: Hungary, Slovakia, Ukraine.

How to check oak pellets

1. Ash — the first indicator of raw-material cleanliness; see ash.
2. Ash deformation temperature — without species-specific data, this is the only way to assess the risk of clinker (more).
3. Nitrogen — up to 0.3% on a dry basis for A1^[1] (chlorine, sulphur, nitrogen).
4. Mechanical durability and bulk density — instead of assuming that “oak is hard”, check the result (durability, bulk density).
5. Certificate — in the ENplus register, not on a copy (how).