Air Quality

Smoke Emissions From Residential Buildings

There have been a number of high profile headlines in the national press recently regarding the smoke emissions from wood burning in residential areas, particularly in and around London, and that one solution under consideration was the banning of wood burning stoves.

Although claims that stoves could be banned were certainly wide of the mark; being subsequently refuted by the Mayor of London’s office, Government and Industry have been working to tackle this problem:

  • The Government backed Ready to Burn scheme was launched in 2017.  Firewood or manufactured Heat Logs that has been certified with a moisture content of less than 20 percent can carry the Ready to Burn logo.  This scheme is designed to raise awareness of the issues and is a clear visual indicator to consumers that the product they are purchasing is certified as being low in moisture and, therefore, low in smoke.
  • Authorised smokeless fuels are actively being promoted as environmentally friendlier alternatives to house coal, with much lower smoke emissions.
 
The important distinction to make is that there are right and wrong types of fuel.  When consumers burn the wrong types it leads to increased smoke emissions and problems with air quality.  The right types of fuel available on the market have low smoke emissions and higher heat outputs and in the case of wood fuels are all characterised by one thing – they are dry, with a moisture content of less than 20%.
 
The following table illustrates the emissions from different types of fuel:

Fuel

 

Smoke (PM2.5) emissions

Wet Wood (over 25% moisture content)

 

25 grammes per hour

Dry Wood (less than 20% moisture)

 

5 grammes per hour

House Coal

 

25 grammes per hour

Authorised Smokeless Fuel

 

5 grammes per hour

The above smoke emissions data is based on independent fuel testing data.

Defra

Why is the Government focused on wood and solid fuel burning in the home?

• Behind the headlines there are a number of factors which have increased the emphasis on burning low emission fuels
• Over the past few years the impact on people’s health from breathing in small airborne particles (technically Particulate Matter below 2.5 Microns in size (PM2.5)) has become clear and hence the increased focus on these emissions
• Such particles not only cause lung congestion and increase the incidence of asthma and respiratory diseases, but are known to pass into the blood stream and contribute to heart disease, as well as being potential carcinogens.  The Department for Environment, Food and Rural Affairs (DEFRA) estimates that 25,000 premature deaths per year in the UK are caused by PM2.5 pollution
• DEFRA has recently issued an assessment of small particle emissions.  This estimates that 100,000 tonnes of these particles are emitted in the UK, with circa 37 percent of these emissions coming from home burning
• This compares with 14 percent of PM2.5 emissions from diesel car exhausts
 

Currently approximately 2.5 million tonnes of firewood and 0.75 million tonnes of solid fuel is burnt in UK homes each year.  At present only 10 percent of the firewood burnt is kiln dried wood of less than 20 percent moisture.  Although a substantial amount of wood is seasoned, a lot of wood is over 20 percent moisture and contributes significantly to PM2.5 pollution.    Looking at solid fuels, circa 300,000 to 350,000 tonnes of house coal is burnt per year, which generates five times the PM2.5 pollution of authorised smokeless fuels. 

Should all the burning of house coal and wet wood in the home be converted to either dry firewood or authorised smokeless coal, then particulate emissions from the home could be reduced by between 70 and 80 percent, reducing total UK PM2.5 pollution by up to 29 percent.

Kiln Dried or Seasoned Wood?

When first felled , wood contains up to 60 percent moisture and is unsuitable for burning.  The wood is stacked within the forest where the natural seasoning (drying out) process starts and then transported.  Despite this initial drying period, the wood still has a moisture content of up to 45 percent when presented for chopping or packing.

Wood can be dried further, by two methods.

Kiln Dried Log Store

Kiln drying the wood, allows it to be quickly dried to a moisture level of less than 20% under a controlled method that involves placing the wood in a controlled kiln environment for between 3 and 7 days at temperatures up to 100 degrees Celsius.  Moisture is measured during and at the end of the process, by the use of moisture meters or through lab testing of samples by completely drying the wood and measuring the moisture / weight loss, to ensure the 20 percent moisture content is achieved.

Seasoning involves stacking the wood and allowing it to dry naturally in barns or shelters.  The length of time and the effectiveness of the seasoning will vary and hence the moisture content will vary significantly, unless a similar control system to that used for kiln dried wood is employed.

Testing by independent laboratories has shown that burning wood with less than 20 percent moisture content very significantly reduces smoke particle emissions.  Kiln Dried wood that has achieved Ready to Burn approval is the best assurance that the 20 percent moisture content has been achieved, resulting in a product that is not only superior in terms of heat output, but has smoke emissions of five times less than freshly felled wood.

Homefire Kiln Dried Logs

Does it cost more to enjoy a fire with the right fuels?

No.  Both in the case of authorised smokeless solid fuels and Ready to Burn kiln dried wood, these low emissions fuels offer better value to consumers than house coal or wet wood.

In the case of smokeless solid fuels, they have lower volatile gas content and so while burning with less of a flame than coal they burn up to 30 percent more efficiently.  (Result supported by independent testing over many years).  In practical terms, the smokeless solid fuel releases 30 percent more heat into the room per kilogram burnt than house coal, so whilst the bag price might be circa 20 percent higher in cost, the actual heating cost is 10 to 14 percent lower.  This is supported by SEAI findings in Ireland and independent testing in the UK.

Please see the table below:

 

House Coal

 

Smokeless Fuel

Price per 10kg

£2.99

 

£3.99

Price per tonne

£299

 

£399

Energy Content (Kwh per tonne)

7900

 

8850

Burning Efficiency (energy in fuel compared to heat in room)

28%

 

37%

Effective Kwh in room per tonne

2212

 

3274

Cost per Kwh in Room

£0.135

 

£0.12

Consumers see a similar picture when burning Ready to Burn firewood compared to unseasoned wood.
 
Independent testing shows kiln dried wood burns with 85 percent greater efficiency than wet, unseasoned wood. In common sense terms, when purchasing unseasoned wood at 45 percent moisture the consumer is paying for 25 percent water compared to kiln dried. 
 
Water and fire don’t mix well, interfering with combustion and the incomplete use of the volatile gasses in the wood, leading to greatly reduced efficiency.
 
Despite kiln dried firewood being up to 40 percent more expensive for a given volume of wood it represents equivalent or better heating value compared to wet, unseasoned wood.

The following table compares kiln dried and unseasoned wood:
 

 

Radiant Heat*
(Kwh per kg)

Price per m3

Price per kg

Price per Radiant Heat

Unseasoned Wood

0.38

£75

£0.15

£0.39

Kiln Dried wood (Less than 20% moisture) 

0.62

£120

£0.24

£0.39

*Radiant Heat represents heat released into the room i.e. useable heat

Conclusion

There is no doubt that having a fire on a winter’s evening is a pleasure for many people.  Doing so can still be environmentally responsible, providing the right fuels such as authorised smokeless fuels or Ready to Burn Firewood are used, helping to reduce smoke and particulates by up to five times compared to wet unseasoned wood and house coal.

The Ready to Burn scheme, recently launched by DEFRA provides consumers with an easy way to identify firewood products, including manufactured heat logs, that have a moisture content of less than 20 percent and are, therefore, are better for the environment; burning with reduced particulates.

Smokeless solid fuels provide another solution, having been developed to address the same issue of air quality back in the 1950’s.

Ecoal

Homefire has been a leader in the area of smokeless solid fuels for many years.  As well as providing smokeless fuels from coal-based sources, Homefire has lead the market with the development of Ecoal Smokeless Fuel – a blended biomass/fossil fuel that not only meets regulated low smoke limits, but also has Carbon Dioxide emissions up to 40 percent lower than house coal when burnt. 

In 2017 Homefire continues to focus on new, environmentally friendlier fuels, with the launch of Homefire Supercharged Heat Logs to market.  This is a fully renewable, low smoke, wood-based product, manufactured using a new process called Torrefaction to provide a fuel with 30 percent more energy than kiln dried wood and with a longer lasting fire.

The Clean Air Act And Smokeless Zones Explained

In the past, many towns and cities of the UK suffered with terrible smog, caused by the widespread use of coal fires in homes. The Clean Air Act, introduced in 1956 was one of several government measures introduced to help reduce smoke pollution and improve the quality of the air that we breathe.

Smokeless Zones

Smokeless zones were introduced as a direct result of the Clean Air Act.  Many parts of the UK are now designated smoke control areas (also known as smokeless zones). In a smokeless zone you can only burn approved smokeless fuels such as Homefire, Ecoal50 or Phurnacite.  

Firewood is not an authorised fuel and cannot be used in smokeless zones, unless burnt on a DEFRA exempt appliance (see below). 

To find out if your property is within a smokeless zone, you will need to speak to your local council, who set the zones and are responsible for enforcement.

Exempt Appliances

Firewood can be burnt in a smokeless zone, but only on a specially designed exempt appliance. However this does not mean you can simply burn anything on an exempt appliance and you should always refer to the appliance manufacturer’s guidelines  as to which fuels can be used.

The Situation Today

With the introduction of the measures above, coupled with the widespread consumer switch from coal to gas fired heating, air quality had improved dramatically since the 1950's.  However, that trend has seen a reverse in recent years.  Air quality; particularly in urban areas, has been getting worse.  This has been caused by the increased number of diesel cars and lorries on our roads, but also the rise in the popularity of wood burning stoves.

Woodsure Ready To Burn

Ready to Burn

Ready to Burn is a scheme backed by Government, fuel suppliers and retailers to encourage home owners to only burn kiln dried firewood.  Kiln dried firewood produces significantly less smoke than wet wood when burnt, so a shift towards burning kiln dried will have a positive affect on air quality.  The scheme was launched in October 2017.

Government Calls For Cleaner, More Efficient Fuels In Air Quality Report

Clean Air Act Explained

Back in the 1950’s, the burning of coal was blamed for the Great Smog of 1952, which resulted in the deaths of around 4,000 Londoners and the introduction of smokeless zones in many urban areas across the UK, where the burning of coal is banned.

We know these days that several factors contribute to dirty air across the UK, including high levels of particulates from diesel car engines and the increasing popularity of burning firewood on wood-burning stoves.

Recently the Government also issued an updated air quality report acknowledging the need to work with solid fuel retailers to make a shift towards using more efficient, cleaner fuels and stoves.

So, as your solid fuel provider, we’re writing to let you know that you’re doing exactly the right thing if you are already using Homefire’s range of high-performing smokeless fuels on your fires and multi-fuel stoves.

These fuels were developed specifically to reduce smoke. Compared to house coal they emit up to 80% less smoke and are therefore authorised for use in smokeless zones.

Equally, we appreciate that many of our long-standing customers have been happy buying traditional house coal or anthracite from Coals2U for many years, but now we’d like to introduce you to Homefire’s range of high performing smokeless fuels.

The benefits of Homefire’s smokeless fuels are numerous: Consistently higher heat than ordinary house coal, more economical, better for your health and better for your appliance. 

Smokeless fuels also produce far fewer harmful particulates and were developed to combat this exact problem of air pollution whilst still allowing people living in smokeless zones fuels that they could use on their fireplace.

With a wealth of industry knowledge and a team of expert staff, we also feel it is important to share information and provide guidance wherever we can on using the right fuel in the right appliance.

Tackling Air Pollution Whilst Enjoying The Healthy Glow Of A Fire

Air pollution in towns and cities is an increasing concern for citizens, health professionals, consumers and the media. Whilst interest in the media and elsewhere has centered on NO2 emissions that arise from diesel vehicles, solid fuels such as wood and coal which are used by millions of homeowners for space heating may be an even greater issue. Every year an estimated 750,000 tonnes of coal and 1.7 -2 million tonnes of wood are burnt by UK households for warmth, often used in heating devices such as log burning stoves and open fires.

By far the most serious pollutant in terms of premature deaths is actually particulate matter (PM2.5). Annually, an estimated 40,000 deaths are linked to air pollution. According to independent reports by the Royal College of Physicians 29,000 of those deaths are caused by exposure to PM2.5 in the UK. The associated costs to the NHS and the economy (in terms of working days lost) is estimated at more than £20 billion every year (RCP 2016).[1]

As one of the UK’s largest solid fuel suppliers, Homefire recognises that the fuel burnt for heating in coal fires and log-burning stoves can be a significant contributor to air pollution in urban areas, especially on winter evenings. There is a need to change the way we think about, generate and use energy in a way which limits our impact on health and the environment. There is also a need to move homes that use coal and other highly polluting fossil fuels toward low carbon and renewable heating sources to ensure we create an environment and living and work spaces fit for future generations.

Via a call for evidence, Defra[2] recently sought information on the use of solid fuels such as house coal, manufactured solid fuel, and wood for domestic heating, and the impact that changes to the availability of these fuels would have on consumers and businesses. Both the Sustainable Energy Association and Homefire Industries responded to this call for evidence.

Both smokeless fuel and kiln-dried wood emit 75-80% less particulate matter (PM2.5) than the equivalent raw coal or unconditioned wood (see figure 1 below). They also offer better heat output and burn for longer; many independent tests support this improved heat output and the Sustainable Energy Authority Ireland data clearly shows that smokeless fuels are better value than coal.

Such a legislative framework also creates an environment for the development of wood fuels and biofuels which utilise residues to produce high-quality low emission fully renewable fuels.

The following gives a brief description of the hydrothermal carbonisation plant nearing completion at Homefire Immingham manufacturing Centre.

This technology creates the potential for second-generation biofuels contributing to a circular economy as well as air quality.