BS EN ISO 17225-4:2021

What is ISO 17225-4 about? 

ISO 17225-4 determines the fuel quality classes and specifications of graded wood chips.  

ISO 17225-4 covers only wood chips produced from the following raw materials: 

• Forest, plantation, and other virgin wood 
• By-products and residues from the wood processing industry 
• Chemically untreated used wood 

NOTE 1: ISO 17225- 4 covers only wood chips, which are produced with sharp tools, and does not cover hog fuel, which is produced with blunt tools. 

NOTE 2: Wood briquettes produced according to ISO 17225-4 can be used in boilers. 

NOTE 3: ISO 17225-4 supports the use of graded wood chips for small and medium residential, commercial and public building applications. 

Who is ISO 17225-4 for?  

ISO 17225-4 on graded wood chips is beneficial for: 

• Biofuel engineers 
• Biodiesel operators 
• Biochemical engineers 
• Biodiesel producers 
• Manufacturers and processors of solid wood products 

Why should you use ISO 17225-4? 

Wood chips is used as a biomass solid fuel and is raw material for producing pulp. Wood chip is also used as an organic mulch in gardening, landscaping, and ecosystem restoration.  

The main objective of ISO 17225-4 is to provide the user with unambiguous and clear classification principles for solid biofuels and to serve as a tool that enable efficient trading of solid biofuels 

ISO 17225-4 enables good understanding between seller and buyer as well as a tool for communication with equipment manufacturers. 

ISO 17225-4 facilitates authority permission procedures and reporting.  

ISO 17225-4 supports the use of graded wood chips for small and medium residential, commercial, and public building applications. 

Depending on the type of energy conversion technology used the tolerances for a particular quality of wood chips will be different. 

Scales of applications and their typical operation range: 

• Below 100 kW (Residential) 
• From 75 to 500 kW (Small; e.g. residential, public, and commercial buildings) 
• From 500 kW to 1,5 MW (Medium; public and commercial buildings) 
• 1,5 MW to 5 MW (Large; small industrial facilities and district heating) 
• Over 5 MW (Industrial; recommended to use 'ISO 17225-1 or ISO/DIS 17225-91)) 

The residential, small, and medium commercial and public building applications require high-quality fuel for the following reasons: 

• Small-scale equipment usually does not have advanced controls and flue gas cleaning 
• Appliances are not managed by professional heating engineers 
• Appliances are often located in residential districts 

Overall, ISO 17225-4 assists wood processors with fuel specifications and classes of superior graded wood chips, which helps them to produce more efficient biofuel with higher calorific value. 

What’s changed since the last update?  

BS EN ISO 17225-4: 2021 supersedes BS EN ISO 17225‑4:2014, which is withdrawn. 

BS EN ISO 17225-4: 2021 cancels and replaces the first edition (ISO 172254:2014), which has been technically revised. The main changes compared to the previous edition are as follows: 

• Particle size distribution classification updated 
• Moisture and ash content classes updated