As natural gas prices, along with electricity and oil prices, have risen sharply, many households in both Greece and the rest of Europe have turned to firewood as an alternative to heating this winter.

However, when consumers are asked to buy wood, they should pay particular attention to certain points, as noted by Dr. Georgios Dalos, wood technologist, professor at the University of Thessaly at the Faculty of Forestry, Wood Science and Design.

Types of firewood

Beech, which is efficient in burning, is ideal for a fireplace, as it gives a larger flame, but does not cause the smoke problems that softwoods create. But be careful, because it traps moisture in pockets, causing it to “pop” as it burns and throw out lit chunks of charcoal.

Oak should be preferred for permanent use. It is not a wood that seizes easily, is inconvenient for kindling, but burns slowly and efficiently and sustains the fire longer.

Olive, like oak, should be preferred as it has a longer burn time.

In general, softwoods, such as pine and fir, quickly “seize”, give a large flame and have a very high heat capacity. We should use them mainly for kindling. Be careful when they are used as the main fuel because they can backfire, which can even start a chimney or roof fire.

The wood most commonly used for kindling is low density, burns quickly and produces a large flame.

According to Mr. Dalos, these types of firewood are the main types, but there are other types, such as chestnuts, poplars, hollies, eucalyptus trees, lemon trees, etc.

Which wood is more efficient?

As firewood will again be sold by the cubic meter this year, Mr. Dalos said consumers should focus on how it is stacked, making sure it’s tight.

They must also ask for human trafficking documents, since smuggling is no longer a criminal offense only for the owner, but the person who obtains them is also implicated.

It’s also good to buy beech, oak and hardwoods in general and be careful not to buy conifers and especially pine, as burning them can start a house fire.

As for pellets, consumers should pay attention to the color of the wood, which should be light in color if it is softwood and slightly dark in hardwood, Mr. Dalos notes, adding that in both cases, buyers should check for the smell should refer to fresh wood.

What to pay attention to

Of particular note is the natural drying of logs. Logs begin to lose water in winter, but in March there is a maximum loss of water (about 10%).

During particularly hot summers, fresh wood, split in December and stored under a shed, can already reach 20% moisture levels in June and thus can be sold as finished dry wood. However, in the case of a humid summer, the detected differences are minimal and the value of 20% will be reached, but after a month.

Logs, Mr. Dalos explains, store relatively faster when dry in the early months of winter. This advantage of coated wood is offset by bare wood during the summer months.

The presence of a wooden canopy, especially in very rainy areas, is considered appropriate, as it helps to limit moisture recovery in the subsequent autumn-winter period. Provided that the structural design provides sufficient ventilation (walls with slots), it is highly recommended to store the wood under a canopy.

Compared to torn wood, torn wood reaches a moisture level of 20% after two months. So, in order to achieve 20%, with a higher degree of preservation and to maintain this humidity until autumn, it is proposed to split low-quality round timber into firewood with a diameter of more than 10 cm before natural drying.

During the processing of wood and the preparation of the stack of firewood, it is important to avoid, if possible, the accumulation of other materials on the firewood logs.

The treatment area must have a stable floor (cement or asphalt). Natural drying of logs can be carried out both in open areas and in covered and ventilated areas, but in any case they must be protected from soil moisture and rain.

How firewood is heated

Finally, data on the calorific value of wood are of interest.

The maximum amount of heat released by 1 kg of dry wood mass during complete combustion (calorific value) ranges from 3900-5100 kcal/kg. Hardwoods have a lower calorific value than softwoods, with average values ​​of 4350 kcal/kg and 4700 kcal/kg, respectively.

Higher density wood has a higher calorific value. Softwoods with resin give wood with a higher calorific value, since the resin has a high calorific value (about 8500 kcal/kg). The chemical composition of wood is also of great importance.

Lignin is characterized by high calorific value, on average 6100 kcal/kg, while cellulose fluctuates between 4150 – 4350 kcal/kg.

Studies have shown that the mesothermic value of hardwoods is greater in wood than in bark, while the opposite is true for softwoods, concludes Mr. Dalos in an interview with APE-MPE.