The carbon footprint of wood pellets

Wood: short carbon cycle

Wood pellets have a small carbon footprint. Plants convert sunlight and carbondioxide into sugars. Oxygen is produced as a secondary product. Wood is made of these sugars and so it is a form of solar energy. Biomass is in fact portable, solid, solar energy. By burning wood in a pellet stove or boiler this energy is released in the form of heat. Carbon dioxide is produced and oxygen consumed.

Wood absorbs as much carbon when it is growing as is released when it is burnt. If the wood is harvested sustainably, e.g. Forest Stewardship Council (FSC) labeled wood, approximate the same amount is grown back as is cut. Therefore wood is assumed to be a carbon-neutral energy source.

The Gray energy of wood pellets

Wood pellets are made by drying and compressing the raw material: saw dust. Unless these processes use carbon neutral green energy, wood pellets consume fossil energy or nuclear energy. Not only production but also transport produce fossil-carbon releases. The amounts of fossil fuels used for this purpose differ from one pellet factory to another, and according to the distance and manner of transport of the pellets. We call them 'gray energy'. Unless the factory is very energy inefficient and the pellets are transported over a long distance by truck, the gray energy of wood pellets is only a small fraction of the total embodied energy of the pellets.

Wood pellets vs fuels

Wood pellets with a high to medium content of gray energy will avoid:

• 90% of the carbon emissions attributable to equivalent natural-gas heating,
• 93% of the carbon emissions attributable to equivalent oil-fired heating,
• 96% of the carbon emissions attributable to equivalent direct electric heating,
• 90% of the carbon emissions attributable to equivalent heat-pump heating.

These figures will even improve when low-carbon-footprint wood pellets are compared to other type of heating fuels.

Reducing the transport and using renewable energy at production are necessary to get close to a 100% of avoided carbon dioxide emissions compared to 'classic' heating fuels.