What does firewood mean

firewood

Wood is mankind's oldest fuel. As a renewable raw material, fuelwood has the unbeatable advantage over fossil fuels (such as crude oil, coal, natural gas) that it burns CO2-neutrally, as the amount of carbon dioxide released corresponds to the amount that the tree withdrew from the air during the growth phase.

More than every fourth German household uses wood for heating. There are around 14 million chimneys, tiled stoves and around 1 million wood central heating systems throughout Germany. A good 75% of the heat generated from renewable energies is generated with wood.

Firewood is produced in the course of the trunk wood harvest (unused wood of the crown) and forest care measures (thinning). Foresters and forest owners deliberately refrain from fetching even the last stretch of the forest. Because dead wood is an important habitat for many types of insects and fungi. Fresh logs are best stored split for two winters so that it is really dry. It should have a maximum residual moisture of 25% when burning.

Energy content of the different types of wood

Decisive for the value of firewood is its calorific value. Deciduous and hardwoods have a significantly higher calorific value per cubic meter than hardwoods or softwoods. Oak, beech and ash have the highest calorific value per cubic meter, followed by birch, pine, larch and, to a lesser extent, spruce. In terms of weight, there are only small differences between the different types of wood: 1 m3 of hardwood weighs around 450 kg, provides around 1,900 kWh and replaces around 190 liters of heating oil. Due to its lower weight (approx. 300 kg), 1 m3 of coniferous wood provides only around 1,300 kWh.

Softwood (spruce, pine)
Although it burns hotter (and is good for the lighting process), it also burns down faster. It is also prone to splashing, so it is better to burn it in closed ovens.

beech Burns evenly, embers well and develops almost no flying sparks.

Birch, maple, hornbeam, ash and fruit trees are often sold as mixed wood. Ash has a particularly beautiful flame pattern.

Oak embers well and burns for a long time. The ash content is higher. In the case of oak, an even supply of oxygen is important. It is particularly suitable for log boilers and tiled stoves.

Wood briquettes are an alternative to split logs. They are industrially pressed from dry softwood or hardwood and have a high calorific value due to their low moisture content. The burning behavior is very different.

Wood pellets are small cylindrical pellets made from dried and natural waste wood (wood shavings, sawdust ...). They are pressed under high pressure without the addition of chemical binders. As pellets are made from very dry wood, they have a high calorific value. Incineration in special ovens is particularly efficient and low in pollutants.

Wood chips are also made from scraps of wood. A chopper is used to chop the wood to the size of a matchbox. They are cheaper than pellets, but have a larger volume and require more storage space. In addition, they are less standardized than pellets, there are large differences in terms of type of wood, water content and piece size.

 

Firewood dimensions

Wood is sold as solid cubic meters (logs), cubic meters (cut and stacked) or as loose cubic meters (poured logs, split and sawn). Depending on the processing, 2 to 2.3 cubic meters of firewood can be produced from one cubic meter of wood. When stacked, logs take up about a third less space.

  • 1 solid cubic meter = 1 m³ of wood mass without spaces, is calculated from the thickness and length of the logs before splitting.
  • 1 cubic meter or ster = 1 m³ of layered logs 1 m long with spaces in between and corresponds to approx. 0.7 solid cubic meters.
  • 1 cubic meter (SRM) = 1 m³ poured, unstacked logs, corresponds to approx. 0.71 - 0.82 cubic meters of re-installed, oven-ready wood or approx. 0.4 solid cubic meters.

(Source: Energieagentur Region Göttingen, 2012: "Correct heating with wood")

 

Additional Information:

UBA brochure "Heating with wood": http://www.umweltbundesamt.de

Various flyers on the subject of heating with wood: http://www.3-n.info

Comparison of fuel costs in Germany: http://depi.de