When you choose wood fuel for your fireplace, you ask yourself many questions. What kind of wood fuel has the highest calorific value? Which trees generate the best firewood? Of all the wood fuels present, which one offers greater heat and efficiency? How does heat transfer occur?
This post aims to answer the above questions and educate you on the different types of wood fuel and all the details about them. Therefore, strap on and enjoy the ride.
Characteristics Of Wood
Before anything else, it’s essential to know the different characteristics of wood. So let’s have a look!
1. The Moisture Of The Wood
You often hear that dry wood is better for your fireplace. But, what is the reason behind drying wood? If the wood must be dry, what is the optimum drying point?
The professionals behind buyfirewooddirect.co.uk emphasize that if you don’t want to go through the entire process of cutting and drying wood, you should get ready-made firewood instead. Adequately dried firewood should have less than 40% moisture to burn easily and generate more heat during combustion.
However, you must also bear in mind that firewood with less than 10% humidity will burn quickly and not give enough heat. The firewood must be previously stored for an average of 10-12 months to attain the correct dryness level so that the moisture evaporates.
2. The Hardness Of The Wood
Hardwood is wood with high-density fibres. This density guarantees more degrees of heat in its combustion.
Trees such as :
- Ash
- Red Oak
- Holm Oak
- Beech
provide high-density wood fuel.
However, one of their disadvantages is that due to their density are more difficult to light.
Softwoods are characterized by having a low density in their fibres. They are easier to light, but their calorific value is lower, and they burn faster. Softwood trees include:
- Pine
- Eastern And Western White
- Fir.
In addition, these woods produce explosions and sparks when burning.
3. Different Types Of Trees Produce Different Woods
Wood fuel is cheaper than other heating types, but you cannot burn just any type of wood. Although this isn’t always the case, you must know some trees offer wood that produces toxic gases when burned. Remember, for this reason.
You shouldn’t add treated wood to your fireplace. They can be parts that have been previously pressure-treated or coated with chemicals.
The most common fireplace woods are oak, olive, apple, cherry or almond and maple. Oak is a hard-density wood with high calorific value and slow combustion. This, together with the fact that it is one of the most abundant trees, makes it ideal for fireplaces and stoves.
Olive wood, which is also very common, is also high density. But unlike oak, it produces more flame.
In addition to being hard and of high calorific value, the firewood of the orange tree offers a unique aroma. It is the type of wood most consumed in areas with a high concentration of orange trees.
Despite the type of wood, when burned, they all produce a residue, ash. You might worry about where to dispose of this waste. If you do not have a garden or some plantation where it can serve as fertilizer, you must deposit it in the organic container.
The Main Types of Wood Fuel
Below we discuss the 4 major types of wood fuel.
1. Wood Chips
Wood chips are a renewable energy source derived from national forests. They are a locally produced, environmentally friendly fuel that is not affected by demand volatility or shocks.
Furthermore, the processing of wood chips creates opportunities for the local community. For both of these purposes, wood chips are an excellent fuel source, not just economically but also environmentally.
It’s advantageous to use wood chips over logs because you can easily and automatically feed them into a boiler. Because of this, they are the ideal fuel for larger boilers, although they are quite bulky. Therefore, you require a large fuel store.
- Wood Chips Benefits Over Logs
While you can easily store and transport logs when piled, and the ease of air passage through a log pile makes for faster drying, they are not suitable for automatic handling and feeding. Furthermore, the comparatively low surface area to volume ratio makes effective combustion or gasification impossible.
On the other hand, you can combine wood chips to provide a much more uniform fuel that can flow and burn.
- Producing Wood Chips
Wood chips usually have the longest diameter of between 20-50 mm, depending on the equipment they are to be used in. However, larger chips, which are also known as hog fuel and chunks, can measure up to 100 mm or more. Slivers, which are long thin pieces between the chips can cause blockages in the chip system. So ensure you avoid them.
If you want to produce chips that can suit most boilers, you need to use a specialist chipper built for wood splitting. It helps you to produce evenly sized chips that flow well and without long slivers, which can create jams. Using a general-purpose chipper is not recommended.
- Storing Wood Chips
You should store the wood chips under a shade to protect them from moisture. Also, ensure the place has good airflow to disperse water vapour and prevent decomposition and mould from developing.
- Using Wood Chips In Energy Applications
The bulk energy density in wood chips is between 40 and 50% compared to that of solid wood.
If you need to use wood chips reliably in combustion equipment, more so in domestic or small-scale equipment, they must meet an acceptable quality level. Physical criteria such as maximum size and absence of slivers or fines (sawdust) and maximum moisture content are critical for ensuring stable operation and preventing feed blockages.
- Characteristics Wood Chips
The properties of wood chips are determined by both the chipper and the material used to make them. They are classified as follows:
Forest chips, which include:
- Log chips which are made from delimbed stem wood
- Whole tree chips that are made from all of a tree’s above-ground biomass
- Logging residue chips which are made from branches, brash, and other debris
- Stump chips made from stumps
- Chips made from raw wood residues, reclaimed wood, and off-cuts
- Sawing residue chips which are made from sawmill residues
- Short rotation forestry chips which are made from the respective energy crops
2. Biomass Briquettes
Briquettes are similar to wood pellets but bigger. This can range from about 50 mm to 100 mm in diameter or more. Briquettes are about 60 mm to 150 mm in length. They can provide a safer, more reliable alternative to firewood logs, with higher energy density and consistent combustion.
Briquettes look like conventional firewood logs and are formed after compressing wood shaving and other different types of biomass. Although they resemble logs, briquettes are dryer and denser.
What Makes Wood Briquettes?
The most popular wood briquettes are made from wood shavings, but you can also find briquettes made from other types of biomass.
- Using Briquettes
You can use briquettes instead of firewood logs. Because of their higher energy capacity, they are especially suitable where storage space is small. They are generally cleaner than conventional logs and offer more consistent combustion.
They are much more stable and burn more slowly. But different briquettes are purposefully made with varying burning properties for different markets.
3. The Wood Pellets
Pellet is a wood fuel, like firewood or briquette, and is characterized by its controlled combustion. Once combustion has started, which is not easy to achieve, you can add pellets, as you would do with coal, for example. Constantly adding the coals ensures the temperature is maintained. Then the embers are formed. The wood pellet can work in a stove with a burner that feeds the pellet, a container where this wood is placed. The container is equipped with electronics that control the combustion.
The pellets are created by compressing dried sawdust under very high pressure and extruding it via a die. A small amount of binder like starch is sometimes added, but many depend solely on steam.
Pellets are the most complex biofuel. They are small and cylindrical with a diameter of 6 to 8 mm and a length of 10 to 40 mm made by pressing wood sawdust. You can shape small cylinders or pellets without using any additives because lignin is a natural component of wood that serves as glue.
The key benefits of wood pellets are:
- The calorific value is high. Its homogeneity and constant structure allow for good energy yields.
- Minimum ash content, which eliminates the need for stove and boiler service and maintenance
- Maximum availability in 100% of the territory
- Ease of delivery, in bags or bulk
- Low cost in comparison to fossil fuels
- It functions as a fluid, making it easier to use
4. Logs And Firewood
Firewood logs are the most basic and common kind of wood fuel. The only processing needed is drying and cutting to a scale that fits comfortably in your stove or boiler.
As a fuel, firewood logs have the significant benefit of being easily obtained from one’s forest or trees using only a chainsaw and sufficient safety equipment. Because of the actual size of the logs, it is vital that it is adequately dried, ideally down to 20-25 per cent moisture content (wet basis), which usually requires two years of seasoning.
- Cutting, Stacking and Drying
Small round wood is cut into logs in the forest for ease of extraction and handling. Cutting the wood into logs also aids in drying. You can stack the wood logs on the roadside to dry and transport them later. Piled split and round logs have a bulk density of up to 70% if well stacked, but if loosely stacked, the bulky density drops to 40% and below. The partial removal of log barks, also known as scouring, can fasten the drying process. Splitting bigger logs also aids in drying.
- Recommended Size for Firewood
You can use firewood logs in open fireplaces without splitting them. So you can sell them just as they are to domestic users. The recommended size is 15-50cm long. However, 25-30cm is the optimum size for most domestic users. If the diameter is greater than 10cm, ensure you split them.
- How to Choose, Cut and Store Firewood
The best time of year to cut firewood is in winter when the sap has dropped, and the wood is less humid. Choose firewood that comes from healthy and strong wood, from trees in good condition. The most practical thing to do is to use a chainsaw to cut tree branches or fallen trunks.
Once you collect the wood, you can use different cutting techniques to divide the firewood and obtain smaller pieces to suit your fireplace. You can also use a chainsaw or a cutting machine for crosscuts. Sometimes it’s convenient to use a wedge and a mallet which allows you to take advantage of the cracks in the wood to split it.
Summing Up
Firewood is one of the most significant sources of fuel. It’s a renewable source and relatively safe. However, whatever technique you use to fetch firewood, always take the appropriate preventive measures and protect yourself with good equipment (gloves, glasses, boots, and helmets). It’s preferable to fetch firewood in spring so that it begins to dry with the first heat.
The drying process of the firewood is critical. The drying process allows the wood to release some humidity. As such, the wood gets to the optimal condition to provide the best heat in the fireplace. You should stack the pieces of wood outdoors, protected from the rain.
You can also use a tarp so that they do not touch the ground. The pieces of firewood should not be too close to each other to allow air to pass through. When air passes through unhindered, the wood dries better.
And you only have to let a few months pass, around six to eight is enough, and your firewood will be perfectly ready for next winter.