The 20/20/20 target for Europe, i.e. to decrease the emissions of greenhouse gases by 20% and to increase the use of renewable energy to 20% by the year 2020, will lead to an increased use of Biomass combustion, e.g. by using wood logs and wood pellets for heating. On the other hand, the Air Quality Directive (2008/50/EC) lies down stringent requirements on maximum levels of particulate matter (PM) in the ambient air. Solid fuel burning appliances and boilers produce particulate matter emissions (PME) which are of concern to authorities and the public. The soot and organic components of these emissions are of most concern because they include compounds known for their potential impact on health and environment. Because of their small size, generally of the order of 1 micrometer, they readily ass through the nose and throat into the lungs. Some organic gaseous carbons (OGC) in the flue gas are precursors for secondary organic aerosols (SOA) formed in the atmosphere due to photo---oxidation under the influence of UV---radiation. Many different methods have historically been used to measure PME from the flue gas of solid fuel fired residential appliances and boilers. Confusion has arisen in the market as different and conflicting results have been quoted in manufacturers’ literature. It became important to agree on a method applicable for all types of residential appliances and boilers burning solid fuels. This method shall give repeatable results that are of a guaranteed traceable accuracy, and by this means give the consumer reliable information on the suitability of a particular appliance or boiler.
In January 2012 the joint European Conormative Research Project Common European method for the determination of particulate matter emissions of solid fuel burning appliances and boilers (EN-PME-TEST) started. Its aim was to develop and validate a common European test method to determine particle matter emissions from residential heating appliances and boilers burning solid fuels. The project group is a well balanced consortium of research and test establishments comprising some18 partners from 10 European countries, coordinated by INERIS, France. The project has been performed under the umbrella of the ERANET Bioenergy. Special emphasis was given to the scientific basis for the candidate method and its relevance to health and environmental issues. Following the work performed in the project, a method, designed to be standardized in the short Term and to meet the actual EN standards for appliances and boilers has been selected. It is based On well known measurement techniques. It consists of the collection of the solid and liquid fraction (primary aerosols, PA) in the flue gas using a heated filter and the measurement of OGC using a FID analyzer. OGC are considered as good indicators of the quality of the combustion as well as primary organic aerosols (POA), they are also considered as SOA precursors. As a result, they appear as an interesting parameter to be included in a reference method in order to take into account the impact of wood combustion on air quality. Primary aerosols measured by heated filters at a specific temperature, referred to as PMHF, and OGC sampling gas trains are kept at the identical temperature of 180°C. For the definition of the method, the parameters that have influence on the measurement result, such as temperature control, have particularly been tested. The choice has been made according to the following criteria:
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suitability of the parameters measured regarding impact on air quality
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capability of the method to discriminate the performance of the tested appliances and boilers
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reliability of the results obtained
- availability, cost and simplicity of use of the proposed method, taking into account the fact that it should be used by notified bodies for type testing as well as by industry for product development.
The uncertainty of the method has been determined. The emission values for the expanded uncertainty of a pellet/woodchip boiler obtained are 34% for PMHF in the range between 6 and 42 mg/m3 STP and 30% for OGC in the range between 16 and 144 Ceqmg/m3 STP. The PMHF values for a wood log stove achieved an expanded uncertainty of 35% for PMHF values between 41 and 104 mg/m3 STP. The wood log stove emission values of uncertainty were achieved provided that the sample gas flow in the probe was higher than 7 m/s (typically 7 to 9 m/s). Other methods that better address the issue of impact on air quality such as the use of a micro-smog-chamber (MSC) combined with total carbon measurements (TC) and the use of dilution with filtered air prior to sampling and online mass measurement have been evaluated. Although these methods are of interest, they do not appear mature enough to be proposed as candidate method at a European level right now. They are interesting options for the long term method, but further studies have to be performed.
