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Wood Pellets Quality Standards Review

By Jack Huang    Nov 10, 2014
Wood pellet quality standards
Wood pellet standards

Wood pellets

Wood pellets which are made from compressed sawdust or other raw materials are a heating fuel. Due to the rising prices of commodities and the consistent rise in the cost of fossil fuels, moreover, there is increased attention to the effects on the environment for the using of fossil fuels such as oil and gas. Consequently, wood pellets become popular all over the world. According to the International Energy Agency, wood pellets production has more than doubled between 2006 and 2010 to over 14 million tons. When wood pellets are burned, they can generate high temperature, if the quality can’t be guaranteed, the consequence will be severe, especially on smaller boilers and stoves used for household, so it is important to formulate wood pellets quality standards.

wood pellet specification norms and standards and quality marks
Overview on existing and future system for wood pellet quality specification

Various Wood Pellet Standards

There are some most commonly wood pellets quality standards schemes for certification: ENplus, American Pellet Fuels Institute Standards Program, CANplus (Canada), the French NF system, Ö-Norm (Austria) and DINplus (Germany) and so on. ENplus is the most widely used and the newest one which certified the wood pellets quality standards in Europe. They set the wood pellets quality standards. And in many ways they are similar, the significant difference is they are suitable in different areas or market. For instance, the products of Anyang GEMCO Energy Machinery Co, Ltd have obtained CE certification which means they can access to the European market without considering the respectively certifications. Apart from these, there are some other institutions devote themselves to the certification of wood pellets quality standards.
wood pellets standards marks
Wood pellet standard marks

Key indcaters of wood pellet quality

Even though wood pellets standards varies with different areas or markets, they share the core indicators. According to the requirements of their terms of different standards, about the wood pellets quality standards we should consider the following crucial indicators:

Ash content

We clearly understand wood pellets are generally for heating. Compared with fossil fuels, wood pellets release much less ash. Then what’s the standard of ash content?

According to Pellet Fuels Institute (PFI), the new standard about ash content requirements of wood pellets is as follows:

  • Super-Premium - <0.5% Ash
  • Premium - <1% Ash
  • Standard - <2% Ash
  • Utility - <6% Ash

While the important quality criteria of wood pellets ash content of ENplus which is the benchmark for wood pellets is that at 550 °C for ENplus -A1(the premium quality used in private household boilers or stoves) is≤0.7%/mass, and for ENplus -A2 (used in larger installations) is≤1.5%/mass.

Ash content is one of the indicators of quality standards for wood pellets, from the above description, ash content of qualified wood pellets should be below three percent.

Moisture content

One of the reasons that wood pellets are popular all over the world is that its moisture content is ralatively reasonable for heating compared to some raw materials. Now that the primary purpose of wood pellets is for heating, so the lower the moisture content is, the higher utiliztion rate it is. In accordance with European Pellet Quality Certification (DIN51731 or Ö-Norm which refers to Austrian Standards Institute- Österreichisches Normungsinstitut M-7135), no matter for household or industrial, the requirement of moisture content is less than or equal to 10 w-%, otherwise the wood pellets will not be burned completely.

Bulk density

This is another standard which can determine the quality of wood pellets. It mainly refers to the wood pellet mass per cubic foot. The bulk density of wood pellets is much higher than that of wood chips which can improve the cumbustion rate. You can detect the bulk density by this way: Use a kitchen scale to weigh a vessel larger than 1 litre, fill the vessel with wood pellets until it is full and weigh again, then fill the vessel with water and weigh. At last, deduct the weight of the vessel and the weight full of wood pellets, in accordance with the standard of Enplus, the result should be between 0.6-0.7kg/litre due to the bulk density requirement which ranges from 600 to 750kg /m³. However accroding to the Pellet Fuels Institute, it is from 38.0 to 46.0 lb/cubic foot.

Diameter and length

Wood pellets are produced uniformly, generally they are cylinder-shaped. In this case, the diameter and length must be regular, otherwise the wrong size wood pellets may alter combustion conditions which will result in an increase in emissions and a loss of efficiency. To comply with ENPlus standards the diameter must between 6mm and 8mm and the length ranges from 3.15mm to 40mm.


Durability is also a good representative parameter of wood pellets quality standards. Comply with EN Quality Class Specification, the wood pellets quality standard is greater than 97.5%, while in accordance with the PFI, it is more than or equal to 95%.

In addition, there are still some other indicators which determine the wood pellets quality standards, such as fines, ash melting temperature, etc., which will be simplify presented in diagrams in the next section.

Wood pellets quality classification

According to different wood pellet standards, the quality classification of wood pellets are differentiated with each other. EN quality class specification and PFI classification standards are presented in the following diagram for your reference:

EN Quality Class Specification

Quality Parameter Unit ENPlus-A1 ENPlus-A2 EN-B
Diameter mm 6 or 8 +/- 1 6 or 8 +/- 1 6 or 8 +/- 1
Length mm 3.15 - 40 3.15 - 40 3.15 - 40
Bulk Density kg/m3 >600 >600 >600
Net Calorific Value MJ/kg 16.5 - 19 16.5 - 19 16.5 - 19
Moisture % <10 <10 <10
Durability % >97.5 >97.5 >97.5
Ash % <0.7 <1.5 <3
Ash Melting Temp. >1200 >1100 >1100
  • Stem wood
  • Chemically untreated wood residues
  • Wholetreeswithout roots
  • Stem Wood
  •  Logging residues
  • Chemically untreated wood residues
  • Forest, plantation& other virgin wood
  • Chemically untreated wood residues& used wood

PFI residentical / commercial densified fuel standards

On comparing the above two different wood pellets quality standards, it is easy to conclude that the standards for wood pellets are altering all the time, and the certification for wood pellets quality standards is also changing, whereas at the present stage, these wood pellets quality standards can fully meet the requirements, a key advantage of the certifications for wood pellets quality standards is that they guarantee the whole supply chain from production to storage to transport which ensures customers receive a low emission, high combustion rate, high efficient wood pellets. Hence choosing wood pellets which adopt the certification of some institutions is a wise decision.