uThe need to turn up the heating arises usually early this year. But gas and oil have become expensive, and so many Germans are hoarding wood obsessively. Stove builders are fully booked for months and logs are scarce – people buy what they can get their hands on. What then goes up in smoke in the country’s eleven million wood-burning stoves causes great concern for environmental researchers and physicians, but also for climate experts. The country may face the dirtiest winter in decades.
If you want to smell the energy crisis, you only have to step outside the door in the evening. Plumes of smoke spread in the residential areas. Achim Dittler not only criticizes this for olfactory reasons. The aerosol researcher from the Karlsruhe Institute of Technology has been dealing with gas cleaning and air pollution control for years. In his eyes, burning wood is a crime against the environment and health. In terms of energy content, no other fuel releases more pollutants.
Air pollution will increase
Dittler therefore expects the air quality in many residential areas to deteriorate significantly this winter. Especially since not only air-dried beech wood burns in fireplaces and tiled stoves. Often enough everything that burns flies into the flames: lacquered furniture, glazed floorboards, even plastic-coated waste wood. There are lignite briquettes in the hardware store, and nobody should be surprised if the neighbor also throws waste in the oven. It gets particularly bad in the evenings, at night and at weekends, says Dittler. From a certain time onwards it will be “passive smoking for everyone”.
Ralf Zimmermann, who is researching at the Helmholtz Center Munich and the University of Rostock, also assumes that the air pollution will increase significantly, which pollutants the “cozy open fires” release. Unlike oil and gas, wood does not burn completely, especially if the stoves are used incorrectly. This allows soot particles to escape, with pollutants sticking to the surface, including carcinogenic polycyclic aromatic hydrocarbons. Metals would also be released, says the chemist, as well as large amounts of unhealthy gases such as benzene and formaldehyde. If waste wood is also burned with paint or chipboard, “really dangerous emissions” can also occur, including dioxins and hydrocyanic acid.
Lack of monitoring of exposure in residential areas
The main problem is the very small soot particles. The more than eleven million wood stoves and 900,000 pellet heating systems emit more particulate matter than the approximately sixty million cars and trucks in Germany combined. Compared to gas heating, a pellet stove releases 400 times as much fine dust, tiled stoves even a thousand times as much, a total of around one hundred micrograms per megajoule. The smaller the dust, the more dangerous it is, says Zimmermann. In particular, particles with a diameter of less than 2.5 micrometers (fine dust PM 2.5) penetrate deep into the lungs and are significantly more dangerous than the larger fraction (fine dust PM 10).
But what is blown into the residential areas every day is usually not monitored, says Achim Dittler. Villages and small towns would not have to set up measuring stations: “In the countryside, there are simply no measurements,” he says. And the number of measuring points is actually manageable, nationwide there are around 360 stations for the coarser dusts (PM 10) and only 200 for the very fine ones (PM 2.5), says Stefan Gilge from the German Weather Service. However, at PM 2.5 there is only an annual mean value, at PM 10 there is also a daily limit value in addition to the annual mean value. “This already shows that a high temporal resolution is not required,” says Gilge. Comprehensive and therefore legally secure measurements are simply not affordable.