Firewood can be produced from any timber, although some species are more convenient to work with. Also, certain species have lower calorific quality. Best timber, in terms or availability, price, physical and burning features, are Ash, Oak, Alder and Birch.
Firewood is split logs, typically 6 or 8 pieces through the trunk area. This gives nice 8 – 15 cm width pieces. Not only they dry and burn well, but also are handy to put in boxes, bags and later in the fire places.
The length of proper logs is different mainly because of traditions and installed fireplaces or ovens. Logs can be split into 10 cm, if it’s the kindling (fire starter) sticks. 25 cm (or 10 inch) is typical for household in Germany or United Kingdom. 30 to 33 cm is the length well requested in countries like Belgium or France. For specific usage, i.e. pizzeria, also logs of 45 to 50 cm may be well desired.
Firewood production process starts with harvesting the right timber in the forest. Normally, the greater logs are 6 m long. The logs are placed into wood cutter and sliced into desired length trunks. These trunks then roll to a ‘dicing’ knife and become a 6- o 8- part split. Manually, these logs need to be placed into wooden boxes or metal cages.
The firewood is typically sold in 3 quality conditions: fresh cut, air dried (seasoned) or kiln dried. If drying is not performed, the logs in boxes are ready.
Boxes may also be left to dry naturally in wind, but then they have to be covered against moist and rain. In time of 3 to 6 months the firewood gets ventilated and is fit to be burned. However, to achieve the generally accepted level of no more than 25% residual moisture outside of log, in most times the firewood has to be left air-ventilated for longer periods. Seasoned firewood can be called either one, having about 12 months since the cutting moment, or the one with less than 25 % moist.
Most advanced condition is kiln dried firewood. Since the moment of cutting, drying in the kiln allows to have the firewood burning-ready in time of 7 to 10 days.
Packing of firewood is usually made in predetermined size boxes or bags. Timber weight greatly varies from species to species and also even minor differences in residual moisture are significant weight factors. It is therefore generally and universally accepted to measure and count the volume, not the weight.
Firewood boxes are typically produced out of light, second class wooden boards, assembled as a certain crate and placed onto a palette. These crates correspond to Raummeter (RM) or simply cubic meters. The box that has approximated inside dimensions of 99 cm x 99 cm x 102 cm is called a 1RM box. Double height is 2RM. Depending on logs; boxes may also be 1.8 RM, 2.2 RM or even 2.6 RM in size.
The bags are usually made to be easy to carry by hand and would not exceed of weight 9 to 23 kg. The volume is 22, 30, 40 or 60 liters. In case with bags, the firewood volume is still measured in liters and cubic meters.