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Heating with wood chips

Wood chips - Independence from fossil fuels

Heating with wood chips has many advantages: The wood fuel is CO2-neutral, produced domestically and resilient to global crises. Compared with other raw materials, it is much cheaper, because wood chip is usually produced from residual wood from woodland in this country. After drying, the wood is chopped up and can ultimately be used for heating. With wood chip heating systems, you don’t have to compromise on comfort. The boiler automatically provides just the amount of heat desired all the time. The PuroWIN wood chip gasification boiler is also the first boiler to draw in wood chip as standard. 

Windhager wood chip boiler
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Wood chips are defined as mechanically shredded wood that is processed into pieces of wood a few centimetres in size. The small pieces of wood are burned in fully automatically controlled incinerators and guarantee the same convenience as their fossil-fuel competitors.

If you use wood chips for your heating system, you can use the following comparisons as a guide. One solid cubic metre (fm) of wood yields 1.4 cubic metres (rm) and 2.5 loose cubic metres (srm) of wood chips.

Wood chips (average) Split logs Pellets Heating oil Natural gas
2500 kg (air dry) 2500 kg (air dry) 2000 kg 860 kg 840 kg
12500 l 5000 l 3500 l 1000 l 1000000 l
12.5 m³ (srm) 7.5 m³ (rm) 3.5 l 1 m³ 1000 m³

The quality of the wood chips is an important factor in achieving optimum operation of the heating system. Because of the many producers and different types of wood, wood chip is a raw material which comes in many different forms.  PuroWIN is approved for wood chips of classes P16S and P31S and also A1 and A2 If you use these grades, we can guarantee compliance with the specified emission limits without any additional measures such as filter technology or prior cleaning. For ideal system operation, wood chips with a water content of 20–30 percent should be used.

  • Store logs in an airy, sunny place for at least one summer (for wood chips W25-30)
  • Wood chips with a water content > 35% are not suitable for storage (decomposition, formation of mould, self-heating/risk of fire)
  • During summer months with high precipitation, it is advisable to cover the wood that is to be chipped
  • Use natural, chemically untreated wood
  • Ensure low and homogeneous water content (no pockets of moisture)
  • The proportion of needles, leaves, fine twigs, bark should be low
  • Uniform particle size plays a role
  • The wood chips should have smoothly cut edges and not be frayed
  • They should not contain any dirt or foreign bodies

The heating value varies depending on the how coarse or fine the wood chips are, their water content and whether they are made from hardwood or softwood. This means that for different qualities of chips, different amounts of wood chips are required to provide the required level of heat. You can read about the amount of wood chips you will need for your system in the folder “Fuel Info – Wood Chips”.

Different volume units are used for wood. A distinction is made between cubic metres, solid cubic metres and loose cubic metres. The cubic metre is a stack of logs, the outer edges of which are 1 m x 1 m x 1 m. The spaces in between are included in the calculation. The loose cubic metre, on the other hand, is wood that has been loosely poured into a container measuring 1 m x 1 m x 1 m. Here, too, the spaces in between are included in the calculation. There are no gaps in the solid cubic metre. This consists of 1 m³ of solid wood without gaps.

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