Wood Pellets

Wood pellets are classified as a biofuel. The renewable fuel “wood pellets” is differentiated into industrial pellets and pellets for non-industrial use. Industrial pellets are usually of a lower quality and are used as an alternative fuel to heating oilnatural gas and coal for combustion in industrial heating and power plants, e.g. to produce heat and/or electricity. Industrial pellets do not necessarily have to be made exclusively from untreated wood.

The following description refers to wood pellets for use in small furnaces, i.e. in non-industrial facilities. These are standardized cylindrical pellets produced exclusively from dried, natural, untreated wood such as sawdust or wood shavings. Usually wood pellets are up to 45 mm long and have a diameter of about 6 mm, and generally are produced in accordance with the European standard ISO 17225-2 which replaced the former European standard EN 14961-2 in 2014. ISO 17225-2 prescribes that pellets must be compressed without the addition of chemical binders, so that they are pure bioenergy. So the “adhesion” between the wood fibers in wood pellets is caused primarily by the lignin contained in wood, which acts as a “natural glue.”

Based on the European standard, two certification systems have become established on the European market – ENplus and DINplus. ENplus distinguishes between three grades of pellets: A1, A2 and B. A1 represents the highest quality class for wood pellets. DINplus complies with class A1. High fuel quality is an important requirement for trouble-free, efficient operation of a pellet furnace, so a variety of product features are prescribed in the standard, and hence in the associated certification programs.

One important product feature is the calorific value. High-quality wood pellets have a calorific value of around 5 kWh/kg; this means that 2 kg of wood pellets contain about as much energy as 1 liter of heating oil. On account of their compactness and high energy density of approximately 650 kg/m³, they need very little storage space compared with other fuels such as logs or pieces of wood. This is one of the reasons why wood pellets have  become popular as an alternative energy source to oil and natural gas and are used in many countries worldwide for heating.

Pellets are available in bulk form (loose goods), in sacks and in “Big Bags.” Loose goods are used in pellet-powered central heating systems (i.e. pellet boilers and some pellet stoves with automatic feed). Retailers usually deliver loose goods directly to consumers in their own pellet silo trucks. Delivered as bulk, the wood pellets are then blown into the customer’s pellet storage facility (storage room with slanted ground, sack silo, metal silo, underground tank or similar) through a pipe. For major consumers such as municipal and communal facilities, pellets can also be delivered and unloaded with sliding-floor trucks.  

Bagged goods are mainly used in pellet stoves (manually operated stoves for individual rooms) and other applications such as pellet grills. 15 kg bags are the standard size sold in stores, and are usually delivered on pallets. Big Bags are the rarest form of pellet delivery, mostly available on the market as 500kg to 1000kg-Big Bags.