Heating with wood is harmful to health and the environment

At first glance, there are good reasons for heating with wood. It is considered cosy, cheaper than gas and sustainable. In Germany, wood is treated as a climate-friendly fuel and renewable energy. The reason: The carbon dioxide (CO₂) that is released into the atmosphere when wood is burned is bound again by regrowing trees in sustainable forest management.

According to the Federal Ministry of Food and Agriculture (BMEL), more than a million households in Germany use firewood, wood pellets or woodchips as the primary energy source to heat their entire living space. In addition, there are over eleven million so-called single-room fireplaces, such as stoves (as of March 2022).

So far, wood has played a rather subordinate role: According to the Federal Statistical Office, in 2021 only 3.6 percent of new buildings used wood as the primary heating energy source. The effects of the Ukraine war on gas prices could change that: there is a high demand for stoves and heating systems that run on wood or pellets.

That sounds good at first, like a win-win-win situation for people, industry and nature. However, many experts see things differently. Some consider the burning of wood to be a health hazard - such as Achim Dittler from the Karlsruhe Institute of Technology (KIT). "Nothing burns dirtier and more harmful to the climate than wood," says the researcher. Burning wood would release many more pollutants than burning oil or gas, including carbon monoxide, nitrogen oxides, methane and soot.

According to the Federal Environment Agency (UBA), almost half of the wood currently used in Germany is used to generate energy. Heating with gas, on the other hand, has not only lost importance since the war in Ukraine. According to the Federal Statistical Office, the number of approved residential buildings that primarily use gas as an energy source more than halved in the first half of 2022 compared to the first half of 2019. At the same time, the demand for pellet heating systems and stoves is increasing. According to the German Pellet Institute, which belongs to the German Energy Wood and Pellet Association, almost 32,000 pellet heating systems were sold in the first half of 2022 - twelve percent more than in the same period of the previous year.

But the prices for firewood and wood pellets for stoves and heating systems are also rising sharply: in August they were almost 86 percent higher than in the same month last year, as reported by the Federal Statistical Office. Overall consumer prices rose by 7.9 percent over the same period. The statisticians explained that the reasons for the well above-average price increase were not only the increased demand but also the higher procurement and transport costs in the timber industry.

According to the Pellet Institute and the Federal Association for Firewood Trade and Firewood Production, heating with wood is still cheaper than with oil or gas. According to the Pellet Institute, a kilowatt hour generated by burning wood pellets cost an average of around 8.8 cents in the period from January to August – with natural gas around 14.11 cents.

Dittler calls it a "cardinal error" that wood energy is referred to as climate-neutral, sustainable energy in Germany. The Federal Ministry of Economics and Climate Protection also reports that the emission of air pollutants from wood firing is a problem. Therefore, the rules for keeping the air clean when installing and operating wood heating systems have been tightened again this year.

Wolfgang Straff, Head of the Department of Environmental Medicine and Health Assessment at the Federal Environment Agency, specifically warns of the health hazards caused by fine dust when burning wood. "In general and regardless of the source, the inhalation of particulate matter leads to a relatively high burden of disease in the population." For example, cases of lung cancer, cardiovascular diseases and diabetes can be attributed to particulate matter. According to the doctor, between 2010 and 2018, an average of around 17,500 deaths per year were caused by particulate matter in Germany.

So should heating with wood be banned in the future, as some experts are demanding? After all, burning wood is not only dangerous for your health - environmentalists also warn of the consequences for forests. If Pierre Ibisch from the Eberswalde University for Sustainable Development has his way, the promotion of wood burning should be stopped immediately.

Because burning trees is only climate-neutral under certain circumstances. On the one hand, if no greenhouse gases streamed out of the forest floor when they were removed. "Approximately half of the carbon in forest ecosystems is found in the soil," explains the ecologist. Drying out and warming favored the unwanted breakdown of the carbon, which was then released as CO₂. Secondly, the claimed climate neutrality applies at best over longer periods of time and under the condition that harvested trees really grow back.

Even then, newly planted trees would only become carbon sinks with a time lag. Compensating for the “carbon debt” that has arisen will take at least decades. "But we need the immediate avoidance of additional greenhouse gases."

Ibisch sees wood burning as a threat to the forests, which are in poor condition anyway. The productivity of the trees is falling as a result of the climate crisis and forest use. “So while the trees grow worse, we want to use more wood. A fatal combination,” warns the forest expert.

It was only in mid-September that the European Parliament voted to reduce the amount of wood that can be used to generate energy in the future and to restrict financial support from the state. However, wood burning should continue to be considered a renewable energy source.

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