With oil, gas and electricity prices all at recent highs, more households and businesses are looking for efficient ways to heat their properties.
Wood burners – also known as wood burning stoves – are one option and offer the advantage of using a renewable fuel source, as more trees can be planted to replace any burned.
But is this enough of a benefit, or are log burners bad for environmental commitments? It takes time for newly planted trees to grow, and burning wood releases the carbon locked away inside it, adding to air pollution.
As we move towards the end of winter and World Wood Day on March 23rd, it’s a timely moment to ask: are wood burning stoves environmentally friendly, or is there a more environmentally friendly alternative to wood burning stoves for businesses and households?
What is a wood burning stove?
First of all, let’s ask what is a wood burning stove? The classic wood burner is a metal box usually freestanding on short legs, with a metal or glazed front door through which more fuel is added to the burner.
A stove pipe runs from the firebox up a chimney or flue, and the heat of the air coming out of the burner ensures that the combustion gases and any fine particulates (e.g. soot) are carried out of the property via the chimney.
Some wood burning stoves also have a stove top, allowing them to be used for cooking or to boil a kettle, although modern wood burners are used more as a heating source than they are for cooking.
What is particularly beneficial is the ability to adjust the temperature of the stove by adjusting its air controls. This allows the burner to maintain a property at a comfortable temperature with a certain amount of adjustment to prevent it from becoming too hot.
How does a wood burning stove work?
There’s no great secret to how a wood burning stove works – it produces heat by burning wood either in the form of natural timber, or fire logs made of compressed sawdust.
Fuel can be manufactured pellets, softwood or hardwood. You can also burn processed timber, but this is not a good idea, especially if the wood has been treated with preservatives, paint or wood stain, all of which can create harmful fumes when burned.
The ability to control the air flow through the burner means that it can be more efficient than an open fire, and some modern wood burners come with automatic controls to keep the fire burning efficiently for as long as possible.
In some cases, an outside air intake is used to feed cold air into the burner, as it’s more efficient to heat colder air. There can be limits on this, as the air intake must be lower than the burner to prevent back-venting.
Is burning wood bad for the environment?
On the face of it, “Is burning wood bad for the environment?” can appear to be quite a simple question – but it depends on the source of the wood and on how you define ‘harm’ to the environment.
For example, sustainable forestry practices can ensure that for every tree felled for timber, another one is planted. This keeps a constant supply of mature trees without any net deforestation, and managed forests can be kept free from litter to provide a safe habitat for wildlife.
Responsible forestry has been developed over several decades so that present-day logging is completely sustainable, with some species of tree growing to harvestable size in 15-20 years (and Christmas trees in half that time!).
But even with the best efforts, there can be examples of illegal logging behaviour, such as those seen in the fast furniture industry, which makes it difficult to be 100% certain about the responsibility, sustainability and legality of firewood.
Are wood burning stoves environmentally friendly?
In terms of carbon footprint, wood burning stoves are environmentally friendly in that the carbon they release comes from wood, and has previously been removed from the atmosphere by the tree during its growth.
As a result, it’s reasonable to argue both sides of whether or not log burners are bad for environment targets and policies – and also, whether that carbon would stay locked away if the tree were left to live out its natural life span.
- Carbon stored in trees is released naturally when the tree, branches or leaves rot
- Carbon stored in fossil fuels is generally not released unless the fuel is burned
By growing an equivalent number of new trees, it should be possible to make wood burning stoves carbon neutral during use, although there is still the risk of ‘moving’ carbon from one place to another when transporting firewood, leading to air quality issues in urban areas.
Benefits of a wood burning stove
The benefits of a wood burning stove include the aesthetics – many people prefer the look and feel of a real fire, compared with central heating and electric heaters.
Aside from the localised carbon footprint of combustion, wood is a completely renewable and sustainable fuel source, and new tree growth locks away the carbon released by burning wood.
With increasing pressures on non-renewable fossil fuels like oil, coal and natural gas, plus the electricity generated using them, a wood burner gives households and businesses a valuable route to ‘independence’ when it comes to staying warm.
Reasons why log burners are bad for the environment
It’s not all good news for log burners. As mentioned above, there’s a localised carbon footprint associated with burning wood, potentially affecting air quality in urban areas.
There are other unwelcome by-products too, such as smoke and soot, which add to the pollution coming out of the chimney.
Black soot, in particular, can appear as visible residue on buildings and cars, and this would get worse if more premises were heated by wood burners.
Finally, log burners can have negative effects on indoor environments too, increasing the risk of respiratory illnesses among inhabitants.
How much wood does a wood burner use?
In terms of how much wood a wood burner uses, the answer is quite complicated. It depends on factors like the type of wood used, how long you use your burner on a typical day, whether you have a catalytic wood burner, and the air controls settings.
All of this has knock-on effects on how much heat a wood burning stove produces, which can also depend on environmental conditions like ambient air temperature and the air intake temperature.
What wood is best for a wood burning stove?
The best wood for a wood burning stove has been prepared and dried for the specific purpose of being burned as fuel – as opposed to burning offcuts from furniture-making, old skirting boards and damp wood from the forest floor.
Hardwood burns slower but costs more. Softwood can be significantly cheaper so that, even though it burns faster, it’s more economical overall.
Pellet burner stoves (as the name suggests) use specially made wood pellets as their fuel source, allowing scrap wood and biomass to be compressed into highly efficient pellets to burn.
How to make a wood burning stove more efficient
To make a wood burning stove more efficient, you need an efficient fuel source, a significant difference between the input and output air temperature, and a carefully controlled combustion process.
Like any fire, a wood burning stove needs the right supply of oxygen to fully combust its fuel source, which can also ensure it produces carbon dioxide and not hazardous carbon monoxide.
However, it’s important not to allow the fire to burn too freely, as this can lead to excess heat inside the burner itself and, in extreme cases, may warp or crack the metal firebox.
What to look for in an environmentally friendly log burner
If you’re shopping for an environmentally friendly log burner, there are a few options to consider:
- A non-catalytic log burner with automatic air controls
- A catalytic log burner for more efficient combustion
- A pellet burner for more eco-friendly fuel
Remember that all log burners produce at least some smoke, although efficient combustion can reduce the amount of soot produced.
Also make sure that the log burner is the right size for the space you want to heat. Like any heating or cooling system, choosing the right capacity will give you the most efficient and eco-friendly operation over the long term.
Is there a more environmentally friendly alternative to a wood burning stove?
Heat pumps are an environmentally friendly alternative to wood burning stoves and extract thermal energy from the ground or air, before releasing it into the premises to warm the interior.
As an alternative to wood burners, they are generally cheaper to run. They do need a small amount of electricity, and the external unit can produce noise, but overall, heat pumps are currently considered clean and eco-friendly.
Heat pumps are economical, and can be run in reverse in summer to cool interiors – making them a great alternative to wood burning stoves whether you’re worried about efficiency, economy or the environment alike.