Energy content

One hectare’s logging residue heats five houses for a year.

The moisture content of wood affects its heating value and the energy benefit gained. The more moisture there is in the wood, the more of the energy in the dry matter will be used for vaporizing the water and the less energy will be left for energy use.

TBecause of this the logging residue is dried on the logging site, just as split billets are dried in piles.

The type of the industrial plant where the wood is used has an effect to how much moisture is allowed in the chips. A large, modern power plant can use raw material with a higher moisture content, but in a plant of less than one megawatt the moisture content has to be below 40 percent.

As an example, if the moisture content of a tonne of forest chips is 55 percent, its energy content is about two megawatt hours. If the moisture content drops to 35 percent, the energy content rises close to 2.5 megawatt hours.

If the moisture content drops to 35 percent, the energy content rises close to 2.5 megawatt hours.

For example, it is possible to get a hundred megawatt hours forest energy made from logging residue ‒ crowns, branches and stems ‒ from a regeneration-ready spruce-growing forest hectare in Finland. This equals to energy content of 10,000 litres of heating oil. This amount of energy heats five typical private houses in Finland for a year.

In addition, the stumps from one hectare contain some 200 megawatt hours of energy. With this one could heat ten private houses for a year.

About half of fresh wood consists of water, while in a split billet dried and ready for burning only one fifth is water. In summer and sheltered from the weather, split billets take at least two months to dry

About one third of the wood used to heat private houses is birch. One cubic metre of piled birch split billets equals 170 litres of heating oil.

Updated on the 4th of january, 2016.