Burning wood is a highly sustainable and environmentally friendly heating method. Burning wood on a high efficiency stove can create less CO2 than letting the same wood rot on the floor of a forest.
[Of course, wood rotting on a forest floor will provide habitat, food and eventually improve the soil, unlike burning it – but heating with wood is a much more sustainable way to keep warm than any of the viable alternatives, as long as we plant trees to replace those harvested for firewood – Lowimpact.org]
A key element to efficiency and wood burning is ensuring you are burning the right sort of wood and that it is correctly seasoned.
Correctly seasoned wood
Fire wood should have a moisture content of around 20% – too high a moisture content and you will have an ineffective heat output, increases the risks of tar forming in the flue, and potentially increase the risk of carbon monoxide poisoning.
Having a moisture level of fire wood, which is too low can create excessive flame and heat output, causing the fire wood to be consumed too fast. For maximum efficiency, it is important to check the moisture of your fire wood with a moisture meter.
Different types of wood
Below is a list of various types of good firewood, with the various pros and cons of each. They have been generally listed in order, starting with the most efficient.
Ash (genus: Fraxinus)
Ash is thought to be one of the very best woods for burning. Ash creates a steady flame and a good heat output. Unlike other wood, ash can be burnt when green, but like with most wood burns at it’s very best when it is dry.
Pros:
- Creates a steady flame
- Great heat output
- Can be burnt when green
Cons:
- Can produce a slightly thicker smoke compared to other woods
- Not as easy as some woods to split
Oak (genus: Quercus)
Possibly the best know wood in the UK for a range of reasons. It is a popular wood for furniture but also it makes great firewood.
Pros:
- Creates a steady flame
- Great heat output
- Burns slowly
Cons:
- Harder than some woods to split
- Takes a long time (2 yrs) to season
Beech (genus: Fagus)
Beech can be identified by it’s pale cream colour with a pink or brown hue.
Pros:
- Burns very easily
- Good heat output
Cons:
- It can spit when burning
- Needs to be well seasoned
Hawthorn (genus: Crataegus)
Common hawthorn is a deciduous tree native in the UK and across Europe.
Pros:
- Has a good heat output
- Slow and steady burn rate
- Produces little smoke
Cons:
- Can be difficult to split as straight lengths are rare
Elm (genus: Ulmus)
Elms are deciduous and semi-deciduous trees comprising the flowering plant genus Ulmus in the plant family Ulmaceae
Pros:
- Burns very well
- Slow lasting heat
Cons:
- May need assistance from another faster burning wood
- Must be seasoned very well due to high water content
Yew (genus: Taxus)
Yew is a common name given to various species of trees. The name is most prominently given to any of various coniferous trees and shrubs in the genus Taxus.
Pros:
- Produces an intense heat
- Produces a pleasant smell when burning
Cons:
- It is poisonous
Poor firewood species
Apart from the higher performing woods, listed above, there are also woods, which are not ideal fire wood, and you should be aware of, which can include:
Alder – burns very quickly and provides little heat
Elder – burns quickly with not much of a heat output, it also produces lots of smoke
Horse Chestnut – tends to spit a lot and the heat output is far from ideal
Larch – produces a lot of soot deposits, and spits excessively too.
Poplar – has a very slow burn rate and produces a thick black smoke, even when seasoned.
In conclusion
There is a vast range of good woods to use as a heating source in your home. It is open to debate which is the best, but having a knowledge of the ones to consider, and of course the ones to avoid, can really help you, when it comes to finding the perfect wood to keep you warm, in an environmentally friendly, sustainable way.
11 Comments
Surely Burning wood CAN BE a highly sustainable and environmentally friendly heating method? As the provision of…as long as we plant trees to replace those harvested for firewood, is a big if. Especially if this was scaled up to the general population.
Plus I see a lot of monocultre plantations for supplying this wood already 🙁
Wouldn’t passive design supplemented by PV heating be better?
Hi Dani, thanks for your reply and questions raised. Passive design and PV heating is a great choice in new build homes however the vast majority of housing stock is a lot older. Certain measures can be taken in old housing stock but generally these can not be made passive easily. In the majority of homes in the UK, gas central heating is used as the ‘best’ option but in reality unless very well controlled you are heating the whole house when you may only being using one or two rooms. In these circumstance secondary as been researched and proven to be the most economical (and environmentally responsible) way to provide this heating. Using correctly a modern Eco design 2022 wood burning stove with the right wood as explained above is a viable option.
How to season a wood is a sustainable and cost effective way ?
Is sweet chestnut a suitable wood for stoves?
Cheers…
HI Sanjay – A cheap way to season wood is to ensure it is kept in a dry and airy location. Maybe a dry garage or a bespoke made log store.
Hi – I can be good but it spits a lot, so avoid on an open fire, but it’s not so much of an issue with a glass window log burning stove.
How can burning wood on a stove create less CO2 than letting the same wood rot on the floor of a forest?
The carbon in wood has to end up dispersed in the environment eventually, whether it rots or gets burnt, so ultimately, it’s the same. I suppose the reasoning is that when you burn wood, you get ash and charcoal, and there’s still some carbon in it – especially in charcoal (which can be buried to sequester carbon). Technically, it might be right, but eventually, it’s the same. All the carbon that’s produced by the growing plant will end up back in nature when it’s dead, one way or another. Burning wood is carbon neutral. Burning fossil fuels isn’t, because you’re burning sequestered carbon from another geological time period. Releasing that carbon, rather than the carbon that’s being produced by the biosphere, will destroy natural cycles and result in an excess of carbon that can not help but change the climate by trapping heat. It’s a greenhouse gas and all of it is being delivered straight into the atmosphere.
I think that the sentence in question may have muddled the science it is trying to describe. Instead of “CO2”, perhaps “CO2 equivalent” should have been used.
Burning wood will release CO2 and H2O. Obviously, this can be sustainable but only if no fossil fuels are used in the processing, transportation or fertilisation of the plant before it was used, and sufficient living biomass replaces that which has been felled and burnt – therefore on the small, local-scale. It is why large-scale power station burning of biomass is absolutely NOT environmentally friendly (they also mechanically shred it, heat it up, pelletise it, and shred it again, along with their shareholders getting very rich on government subsidies without which they would never burn the stuff).
But, considering only the carbon in a tree: if this wood is felled and left to rot on the ground then certain bacteria can decompose the wood and release methane (CH4) to the atmosphere. It is commonly quoted that CH4 is 21 times more potent as a greenhouse gas than CO2 (the actual evidence is very hard to find but I have traced it back to an old publication by the American EPA). People often use this to support the burning of wood by saying that it is better for greenhouse gas emissions to burn it rather than let it rot. And so there is some truth in it, although the ecological and geochemical interactions are complex. I suspect that this is what Dane means.
So, in simple terms, burning wood on a stove will actually create MORE CO2 than if the wood was left to rot on the floor of the forest. But this might be better for global warming as although there is more CO2, there may be less CH4. Hence “CO2 equivalent”.
Dave could have a valid point, particularly with char from gasification; but not with regard to ash. If the stove works well ash should have zero carbon in it.
Andrew
Hi Andrew, thanks for your comments and I agree I a more accurate phrasing would of been “CO2 equivalent” or maybe “Greenhouse Gases”. Thanks Dane
Thank you for this blog – very interesting and informative, both for my personal use and as research for a book I am writing.