The renewable raw material wood, which burns carbon-neutral and is more cost-efficient than oil or gas, is becoming increasingly significant as a heating fuel. Currently Germany has more than 14 million small wood combustion systems, in which more than 25 million m3 of wood are burned each year. This contributes to climate protection, since only the amount of carbon dioxide needed for the growth of the trees is released.
However, wood combustion systems can cause pollutant emissions, above all fine dust pollution. The highest levels of fine dust pollution in the open air are concentrated primarily in conurbations characterized by heavy traffic and industry. But fine dust from wood combustion systems also makes a substantial contribution to air pollution: the emission levels from systems in homes and small businesses in Germany are already higher than those from car and truck motors. Furthermore, these emissions occur mostly in the winter months, in which a reduced air exchange (thermal inversion) always causes higher levels of fine dust pollution. Without the factor which wood combustion systems represent in the equation, the number of days in the winter half-year (depending on location) upon which the daily fine dust limit value of 50 µg/m3 is exceeded would be reduced by around 50 %.
The main cause of the high levels of pollution emissions is the use of older single-room ovens such as fireplaces or tiled stoves, the emission levels of which are many times higher than those of modern systems. Beginning in 2015, stricter legal limits will come into effect. User behavior patterns and the types of fuel used (see insert) are also major factors. In order to accelerate technical developments in low-emission systems and combustion processes, the DBU called for proposals in a “grant cluster” in 2012 with the title “Emissions Reduction in Biomass-Fuelled Small Combustion Systems”.
Further information on the subject can be found at www.dbu.de/2016.html
