In Germany, millions of wood-burning stoves are used for domestic heating, releasing a significant amount of particulate and gaseous pollutants into the atmosphere. These pollutants include ultrafine soot particles, carbon monoxide, formaldehyde, and polycyclic aromatic hydrocarbons (PAHs), among others. The interaction of these substances poses additional hazards, making it crucial to find effective methods to reduce emissions.
To address this issue, Germany’s First Federal Immission Control Ordinance and the EU’s Ecodesign Directive have set limit values for pollutant emissions from stoves. Abatement devices, such as electrostatic precipitators and catalytic converters, are installed in these stoves to reduce emissions. Electrostatic precipitators charge the particles in flue gas, causing them to precipitate in the flue pipe. On the other hand, catalytic converters convert toxic gaseous substances into non-toxic ones, such as carbon dioxide and water.
While previous studies have focused on specific pollutants in flue gas, the effectiveness of catalytic converters and electrostatic precipitators used in combination has not been thoroughly examined. The collaborative project TeToxBeScheit aimed to address this knowledge gap.
The project, coordinated by the Unit of Technology of Fuels at RWTH Aachen University (TEER), involved scientists from four institutes. They investigated the reduction of pollutant emissions achieved by catalytic converters and electrostatic precipitators separately and in combination. The project also explored the protective effect of these abatement devices on human health and the environment.
The study conducted chemical and physical experiments to analyze the flue gas and particulate matter emissions. The Medical Center—University of Freiburg focused on human toxicology experiments, while Goethe University Frankfurt conducted ecotoxicological experiments. The latter involved evaluating the effect of pollutants and combinations of them on algae, water fleas, and fish embryos.
The ecotoxicological experiments demonstrated the adverse effects of untreated flue gas on aquatic systems. Fish embryos exhibited organ damage, water fleas died, and algae growth was inhibited. However, when a catalytic converter was installed, no adverse effects were observed, and the pollutant load in the aquatic systems significantly decreased. This result was corroborated by chemical and physical measurements.
On the other hand, the electrostatic precipitator proved to be less effective in the firebox. Its effectiveness increased when the device was installed at a greater distance from the firebox, as certain substances only bind to particles in cooled flue gas. The human toxicology experiments conducted at the Medical Center—University of Freiburg also revealed that catalytic converters outperformed electrostatic precipitators in reducing toxicity.
Dr. Sabrina Schiwy from the Department of Evolutionary Ecology & Environmental Toxicology at Goethe University Frankfurt emphasized the effectiveness of catalytic converters in reducing highly reactive substances. She recommended retrofitting stoves with catalytic converters for around €400.
While the immediate effects of electrostatic precipitators in terms of ecotoxicology and human toxicology may be less noticeable, the study highlighted their importance in reducing particulate matter emissions by up to 95%, especially when chronic exposure is considered. Therefore, electrostatic precipitators are crucial as additional abatement measures, filling a gap not covered by catalytic converters.
The study also recommended the combination of electrostatic precipitators and catalytic converters in wood-burning stoves to achieve the best results. Installing the electrostatic precipitator upstream of the catalytic converter allows it to remove particles first, while the catalytic converter addresses gaseous substances.
In light of these findings, the study suggests adjusting the limit values in the First Federal Immission Control Ordinance to reflect the current state of abatement measures. This adjustment would ensure that stoves are not sold or installed without these effective abatement devices. By implementing these improvements, the reduction of pollutants from wood-burning stoves can contribute to improving both human health and environmental well-being.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
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