ISO 17225-2 Solid Biofuels - Fuel Specifications and Classes - Part 2: Classified Wood Pellets

The aim of the ISO 17225 series is to provide clear and explicit classification principles for solid biofuels, to serve as a tool to ensure the efficient trading of solid biofuels, to provide good understanding between sellers and buyers, and to facilitate communication with equipment manufacturers. These standards also simplify authorization procedures and reporting for competent authorities.

The ISO 17225-2 standard supports the use of rated wood pellets for residential, small commercial, and public building applications, as well as industrial energy production applications, that require graded pellet quality. Residential, small commercial, and public building applications require higher quality fuel for the following reasons:

• Small-scale equipment typically lacks advanced controls and flue gas cleaning systems.
• Appliances are not usually managed by professional heating engineers.
• These devices are typically found in residential and housing areas.

Pellets produced according to this standard can be used in pellet stoves tested according to EN 14785, pellet burners tested according to EN 15270, and pellet boilers or integrated pellet burner systems tested according to EN 303–5.

The “ISO 17225-2 Solid biofuels - Fuel properties and classes - Part 2: Classified wood pellets” standard, published by the International Organization for Standardization (ISO), describes the fuel quality classes and characteristics of classified wood pellets for industrial and non-industrial uses. This standard covers only wood pellets produced from the following raw materials:

• Forest, plantation and other virgin wood
• By-products and residues from the wood processing industry
• Used wood that has not been chemically treated

Heat-treated biomass pellets (e.g. torrefied pellets) are not included in the scope of this standard.

In the pursuit of sustainable energy, wood pellets have emerged as a cornerstone of renewable heating and power generation. These compact, cylindrical fuel pellets offer high energy density, low emissions, and ease of use in stoves, boilers, and industrial plants. The ISO 17225-2 standard is fundamental to ensuring their quality. This standard defines precise fuel quality classes (premium (A1/A2) for residential and industrial (I1-I4)) and specifications for wood pellets used in non-industrial (residential or commercial) and industrial applications.

Low-quality pellets can clog burners, increase emissions, and reduce efficiency. This standard protects consumers, enables fair trade, and supports certifications.

The main reason why the ISO 17225-2 standard is important is that it plays a critical role in the energy sector, the environment, and consumer rights by guaranteeing the quality, safety, and sustainability of wood pellets. In short, this standard is considered important for the following reasons:

• Appliance safety and longevity: Thanks to low ash, chlorine, sulfur, and nitrogen content, corrosion, clogging, and slag formation in boilers, stoves, and burners are prevented, maintenance costs are reduced, and the lifespan of the appliance is extended. Class A1 pellets are considered mandatory, especially for household stoves (EN 14785 standard). For example, high-chlorine pellets lead to rust and boiler failure within 2-3 years.
• Environmental protection and low emissions:
• Ash: A1 limit maximum 0.7%. Effect: less particulate emissions.
• Nitrogen: A1 limit maximum 0.1%. Effect: nitric oxide decreases.
• Chlorine: A1 limit maximum 0.02%. Effect: Prevents the formation of hydrochloric acid and dioxins.
• Sulfur: A1 limit maximum 0.04%. Effect: Sulfur dioxide emissions decrease.
• Trade and international market access: Major certification systems are based on the ISO 17225-2 standard. Manufacturers standardize their products with A1, A2, and B labels, gaining credibility. Some importing countries only accept pellets that meet this standard.
• Consumer confidence and reduced complaints: Mandatory labeling (moisture, ash, calories, source) allows consumers to make informed choices, reducing complaints such as "pellets don't burn" or "too much ash." It also prevents unfair competition (low-quality pellets).
• Sustainable forestry and traceability: With the ISO 17225-1 standard, it is possible to trace whether the raw material comes from the forest, sawdust, or is recycled. Wood that has not undergone chemical treatment (paint, glue, varnish) is mandatory.
• Legal and official requirements:
• EU: According to the Ecodesign directive, only A1/A2 pellets can be used.
• Germany: A1 pellets are mandatory.
• Italy: A1 pellets are mandatory.
• Türkiye: The TS EN ISO 17225-2 national standard is valid; it serves as the reference for imports.

In short, the ISO 17225-2 standard solves the problem of poor-quality pellets and makes biomass energy reliable and sustainable. The indispensable nature of this standard is based on the following reasons:

• From a technical standpoint, its contribution is device protection and high efficiency.
• Its environmental contribution is low emissions and clean combustion.
• Its economic contribution is global trade, certification, and trust.
• From the consumer's perspective, the benefit is information, performance, and satisfaction.
• From a legal standpoint, its contribution is mandatory standards and oversight.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the “ISO 17225-2 Solid biofuels - Fuel properties and classes - Part 2: Classified wood pellets” standard.