Combustion of Wood

Useful tips / controls when choosing to burn wood

 
The use of open fires and wood-burning stoves has risen in popularity over recent years.  Domestic wood burning is the single largest contributor to harmful particulate emissions, comprising almost 40% of UK totals in 2015 (Defra, 2016).  This is almost four times the quantity emitted from road transport.  
 
These tiny particles in smoke can cause a range of health impacts such as breathing problems and exacerbating asthma as well as contributing to other health conditions.  The concern regarding small particulate matter and particularly the very small fraction less than 2.5 um (PM2.5) is from the day to day variations in hospital admissions of persons suffering from respiratory, cardiovascular and asthma illnesses.  Mortality burdens by local authority area associated with this particulate matter are shown by Public Health England (PHE, 2014).
 
The legislation to control these emissions (The Clean Air Act 1993) was introduced primarily to control the widespread burning of coal after the Second World War with legislation introduced to reduce impacts from grit and dust.
 
Whilst the burning of coal is now much reduced, we are seeing significant increases being reported by Defra of particulate matter emissions from the domestic wood burning sector (Defra, 2016).  
 
Whilst local authorities can designate and enforce Smoke Control Areas to help reduce these harmful emissions, this does not control widespread burning of wood.  Smoke Control Areas would for example, require burning only the authorised forms of fuel (coal / fire logs etc.), plus require installation of only exempt appliances in these areas.  In the West Somerset area there are no designated Smoke Control Areas especially as the fuel being burnt in the area is primarily wood not coal.  The area is noted for example, to have the largest proportion large biomass (wood) boilers in Somerset.

It is also important to understand the permissions that are also required for new installations as follows;

For new biomass stoves / boilers up to 45 kW these are subject to control through the Building Regulations or its competent persons scheme (HETAS). 

For appliances burning biomass (coal / wood) above the 45kW Building Control threshold the methodology used to control emissions cannot be relied on.  Instead the emissions are subject to assessment under Council’s local air management responsibilities and requirements under the Clean Air Act 1993.

The assessment considers both the significance in any increase in the emissions, which are matters of potential material planning concern and also emission rates when compared to maximum limits.   
 
For non-domestic biomass boilers over the 45kW threshold they will require planning permission, as well needing to comply with section 4 of the Clean Air Act 1993 (smokeless). To help with compliance under the Act, for any biomass boiler over the 45kW the attached form should be completed and returned and marked for the attention of Environmental Health.
 
Given the importance of fuel quality there may in some instances and where appropriate, be the need to apply planning conditions to ensure moisture content of fuel remains within an acceptable range and ensuring there is sufficient dry storage set aside for the wood fuel.
 
Please note, to apply for a Renewable Heat Incentive grant (RHI) they must be accompanied with an emission certificate to prove the boiler has been tested and passed emission checks for the principle pollutants (NOx and PM10).  A biomass boiler which has this level of compliance will help when this authority assesses the plant for approval under the Act.
 
For installations above 20MW threshold they fall under environmental permitting legislation.
 
Where the fuel is waste or waste derived biomass and above 0.4MWth threshold, they require an environmental permit granted by either this Authority or the Environment Agency.  For details and application form please see Defra Process Guidance Note PG 1/12 (13)

Alongside these controls it is also important to understand a few basic steps that can be undertaken to that will not only help protect neighbours health, but also your own when burning these fuels.
 
The attached leaflet from Defra (Practical guide on use of Open Fires and Wood Burning Stoves) explains some of the measures people can take to help reduce impacts from these appliances.  
 
There is also useful guidance issued by chimney sweeps entitled “We all breathe the same air” and includes further guidance and videos to explain procedures to follow when lighting a stove, including;
 
  • Guide of wood moisture meters
  • Stove Fans
  • Flue thermometers
  • Explanation of the Woodsure scheme see the Woodsure leaflet, where you can locate local HETAS assured suppliers. Woodsure suppliers stock wood below a certified moisture level.
Furthermore, given the long operation life-time of stoves and boilers it is important to also consider the efficiency and emission standards of these appliances when purchasing a new appliance or replacing an old one.  
 
New European Eco-design Regulations are being introduced to harmonize emission standards and efficiency criteria for solid fuel boilers and solid fuel local space heaters (e.g. domestic wood burning stoves) with effect from 2020 and 2022 respectively.  They will set emission criteria for a number of key pollutants up to 500KW rated thermal output.  A number of manufacturers already offer some appliances meeting the Eco-Design standard, and can be viewed through an initiative run by the Stove Industry Alliance