We live in an era where politicians project an air of obsession when it comes to the environment and green technology. We have all seen the headlines, massive reductions in CO2 emissions, cleaner power supplies and drastically reduced air pollution. In reality very few if any of these targets are ever met, many are kicked into the long grass for another day before rolling out yet another green policy. Recently the credentials of wood-burning stoves have been under attack amid suggestions that the UK government is looking to tighten regulations and may consider a ban in certain areas.
Amidst the clamour for tighter regulations it is easy to forget that the modern day wood-burning stove may look the same as it did 20 years ago but the inner workings and fine-tuned technology are very different. While there is no doubt that any wood-burning stove creates emissions there is also no doubt that these emissions have been greatly reduced over the last decade.
Coal fires and wood-burning stoves
Before we begin to look at the new technology which has taken wood-burning stove efficiency to a new level, it is worth reminding ourselves how they compare to the likes of coal fires. Over the years we have seen many reports suggesting that the efficiency rating of a traditional coal fire is anywhere between 20% and 30%. This effectively means that between 70% and 80% of the source fuel energy is lost in the burning process. When you bear in mind that a modern day wood-burning stove has an efficiency rating of around 80%, this means that only 20% of the source fuel energy is lost during the combustion process. So, as far as efficiency goes there is no real comparison?
As we touched on above, there have been some major developments in the wood-burning stove combustion process. Those stoves which are approved by DEFRA for use in smoke controlled areas are extremely efficient and well-designed. The combustion process centres round the primary, secondary and tertiary air supply which works as follows:-
Primary air supply
The primary air supply enters your stove through the ash pan or simply through the stove door which remains open during the initial burning process. Many people use kindling to start the burning process which heats the primary air supply. As the air rises in the combustion chamber the temperature begins to rise as more hot air is created. Once the fire has caught hold then the door can be closed and the temperature within the combustion chamber will gradually increase.
Secondary air supply
The vast majority of wood-burning stoves today have what is known as an “air wash system” which ensures that the glass in the stove door remains clear at all times. This secondary air supply is drawn in through vents towards the top of the door, brushing past the stove door glass and cleaning it in the process. This secondary supply is also used to enhance the initial combustion process by joining the primary air supply to ignite fuel and gases in the combustion chamber.
Tertiary air supply
Many modern day wood-burning stoves also offer a tertiary air supply with air drawn in through vents towards the rear of the stove body. The tertiary air supply is very quickly preheated, as the stove temperature increases significantly during the initial combustion process, and used to enhance the combustion process helping to burn off excess gas which would otherwise have left the stove via the flue pipe. It is the burning and re-burning of fuel and gas emissions which has created a machine which is extremely efficient.
Carbon neutral fuel
One issue which is often overlooked by critics of wood-burning stoves is the fact that a tree will absorb more carbon in its lifetime than it will release during the burning process. This essentially means that wood fuel for wood-burning stoves is better than carbon neutral and this is before we even look at the replanting of uprooted trees. When you compare this statistic to other forms of energy/heat creation it is difficult to understand why there is so much criticism of wood-burning stoves today and their greatly reduced emissions. There is no doubt that certain political parties and political movements have an agenda which does not reflect the comparable benefits of wood-burning stoves.
Ever tightening regulations
The vast majority of new stoves today are known as “clean burn” as the need to abide by DEFRA regulations continues to strengthen. DEFRA approval means that a stove can be used in smoke control areas although there is talk of legislation which could ban the use of certain types of stove in smoke control areas when air pollution is relatively high. Whether or not such legislation makes onto the statute books remains to be seen - surely politicians must have more important issues to address?
Back to basics
The reality is that any combustion process will create a variety of different emissions which will have an impact upon the immediate environment. The very fact that wood-burning stoves have been pushed for their “green credentials” in years gone by seems to have conveniently been forgotten by many politicians. We have a machine which loses less than 20% of source fuel energy in the combustion process, is able to burn and re-burn fuel and gases, not to mention based on a fuel source which is carbon neutral at worst.
The proposed introduction of new air pollution regulations will have a greater impact on older stoves but as stove technology continues to improve it is difficult to see anything but greater efficiencies and lower emissions going forward. In simple terms, the modern day stove industry is well ahead of the efficiency curve and continues to strengthen its green credentials.
This article was written by Mark Benson who works for https://www.bowlandstoves.co.uk/. The company offers an array of wood burning and multi-fuel stoves together with spares and accessories.