Tuesday, 07 May 2019

How do timber species compare as fuel for firewood

How do timber species compare as fuel for firewood

Any heat-seeking home combustion fire-lover knows that it’s all about the quality and type of the firewood you burn as to the warmth achieved. To help those that are a bit lost-in-the-forest when it comes to what wood to burn to keep the cold at bay on chilly winter nights, highlighted below are various characteristics of wood that are important to all self-respecting pyromaniacs!

Firewood should be to be seasoned. This means cut and dried for a period of time so that it’s not green – or wet – when using it to burn. A large proportion of the energy generated from burning green firewood actually goes into evaporating the water held in the timber and so, green firewood only gives off about 40% of the energy, or heat, of dry firewood. To get the best out of firewood it should be cut, split, and stacked in a dry ventilated area at least 6 months before use. The longer firewood is seasoned the better the heat it will produce. Green firewood smokes and doesn’t burn well or produce good heat.

The denser the firewood the better. By density we mean the amount of space a mass of firewood occupies per weight. The denser (heavier per space volume) the firewood is, the better its burn time. In other words, the greater the mass a firewood species has, the longer it takes to burn and the greater the time it is able to produce heat. The denser the firewood the better the coals it will produce – which leads to longer lasting and resonant heat.

The more available heat the firewood has the better. Available heat is a measure of the heat given off when the firewood is burnt and is measured in kilojoules per gram of wood. A piece of hardwood (Mallee Root, Redgum, Bluegum, Sugargum) gives off more energy than softwood (pine).

Wood that is easier to split is easier to use. Wood with a straight grain is easier to split and cut with an axe than those with a tighter and more complex grain. Knots, branches and, other defects can also increase this difficulty. Also, dry, seasoned firewood is generally easier to split that green firewood.  However, the catch here is that often very dense woods, like Mallee Wood, have tight complex grants and are incredibly difficult to split.

Ease of ignition is also a factor to consider – especially when getting a fire started. Low-density lightwood is easier to light and will burn more readily – great for getting a fire started but not for burn time. It follows then that the denser the firewood the harder it is to ignite.

Sparks and spitting is also a consideration, especially in open and outdoor fire settings. Sparks or spitting is dependant on the number of extractives. Extractives are waxes, fatty acids, resin acids, and terpenes of a tree and effect its volatility. Woods such as conifer are high in resin and therefore spark. Usually, these types of woods are light and have high ignition qualities.

Cost is also a factor for all wood burners. Usually, firewood is sold per tonne and there is a delivery fee attached. Amount bought comes down to storage ability. Keeping it dry and safe (from theft) is also important.

Using sustainably sourced and plantation grown firewood that is renewable is important to many fire-loving people. Using gas, electricity or burning fossil fuels involves using non-renewable energy resources. Burning timber that is harvested from renewable commercial sources and that are re-planted and regrown accordingly to demand provides a more sustainable option to heat your home this winter.

Environmental concerns are also a factor in deciding what firewood to use, or using wood at all. Dry firewood is a relatively clean fuel. It is low in sulphur emissions and leaves little ash residue when burnt in a conventional wood heater that complies with Australian standards. It can also be argued that burning plantation firewood is carbon neutral provided the trees are regrown as carbon released in the atmosphere during combustion is counteracted by the CO2 absorbed by the new growing crop of trees.

In summary, to get a fire started, a light; easily combustible firewood is an excellent choice for getting a fire started. It is then important to use a seasoned and denser option to provide heat and burn time. If possible it is important to choose timber from a provider that is harvesting from a plantation and sustainable source, not native forests and that a number of timbers are chosen.

Firewood Solutions harvests and provides locally sourced and sustainable firewood that is more affordable, seasoned, split, and delivered to your door to keep you warm this winter!

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