Very low fine dust emissions caused by pellet boilers

Regarding the recent discussion around eco-friendly heating, fine dust pollution caused by wood boilers is a major argument against rewnewables brought up by the fossil fuels lobby. Critics argue that the increased use of biomass for domestic heating leads to air pollution, specifically fine dust pollution whereas the burning of fossil fuels doesn’t generate any substantial amount of fine dust (also known as particulate matter „PM“).

Reduction of fine dust emissions

Fine dust emissions due to outdated heating devices

It’s hardly surprising that this simplistic explanation doesn’t bear examination. Although it is correct that burning wood gives rise to fine dust, the degree of it depends largely on the quality of combustion, the fuel and how the heating installation is operated. Fine dust emissions due to wood burning are mainly caused by outdated heating devices such as old logwood stoves. These manually fired systems often operate at a very low efficiency and due to incomplete combustion emit significant amounts of particulate matter. However, these observations don’t apply to modern, fully-automated wood boilers, especially not to pellet heating systems. In fact, pellet boilers or stoves that replace  old wood heating systems  have the potential to significantly improve air quality and reduce fine dust pollution.

Figure 1

Pellet boilers can reduce fine dust emissions significantly

The combustion technology underlying pellet boilers and stoves reduces fine dust emissions to well below the thresholds specified in Europe and worldwide. Modern pellet heating systems have managed to reduce emissions dramatically by electronic control of the combustion process, high temperatures in the combustion zone and perfect mixing of air and fuel. They also feature efficiency rates of over 90%. The most recent models can be operated in flue gas condensing mode achieving over 100% efficiency based on the lower heating value of the fuel.

Besides reducing emissions the toxicity of emissions has been reduced significantly as well. While emissions from old logwood heating or oil heating systems contain significant amounts of soot and unburnt toxic hydrocarbons, emissions from pellet heating systems are – due to the complete combustion – mostly inorganic salts that are water soluble and considerably less harmful.

Figure 2

Replacing old logwood stoves and boilers by pellet systems leads to a reduction of fine dust emissions of up to 95% and allows to improve air quality without compromising the goal of using renewable energy.

Figure 3

Figure 1 shows the difference in emission levels of fine dust between modern pellet heating systems and other heating systems.
Figure 2 shows the significant difference of the chemical composition of emitted particles. This is another reason why pellet heating systems can notably improve air quality. 
Figure 3 shows that the toxicity of emissions of modern pellet boilers is up to 1000 times lower than the toxicity of emissions caused by old logwood boilers.

Read full study HERE.