Emissions from a thermal soil treatment plant are monitored by a multi-stage surveillance system that combines continuous measurement technology during ongoing operations with regular discontinuous measurements carried out by accredited testing institutes. The basis for this is the requirements of the Federal Immission Control Act (BImSchG) and the 17th BImSchV, which prescribe strict emission limit values for plants involved in the thermal treatment of waste. The following sections answer the most important questions regarding emission monitoring, statutory limit values, and regulatory reporting obligations.
What pollutants are produced during thermal desorption?
During thermal desorption in a rotary kiln, exhaust gases are produced that can contain various pollutants depending on the composition of the treated material. Typical emissions include dust, nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), organic compounds (Cges), heavy metals such as mercury, and polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDF). Hydrogen chloride (HCl) and hydrogen fluoride (HF) may also occur.
Which pollutants are released and at what concentration depends directly on the composition of the soil or demolition debris being processed. Soils contaminated with mineral oil hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), PCBs, BTEX, or chlorinated hydrocarbons produce specific exhaust gas compositions during thermal treatment. Treatment temperatures typically reach up to approximately 600 °C, depending on the material and contaminant load. For this reason, precise input characterization of the material is a prerequisite for controlled plant operation. After leaving the rotary kiln, the exhaust gases are treated in a multi-stage exhaust gas cleaning system before being released into the atmosphere via the stack.
What statutory limit values apply to thermal soil treatment plants?
Thermal soil treatment plants in Germany are subject to the emission limit values of the 17th BImSchV (Ordinance on the Incineration and Co-incineration of Waste). This ordinance sets daily and half-hourly mean values for a wide range of pollutants, including dust, CO, NOx, SO2, HCl, HF, organic compounds, heavy metals, and PCDD/PCDF.
Particularly strict requirements apply to dioxins and furans, whose limit value is 0.1 nanograms of toxicity equivalent per cubic meter. A separate, very low limit value applies to mercury, as this heavy metal is environmentally relevant even at low concentrations. Operators of a thermal soil treatment plant are obligated to demonstrate compliance with these limit values at all times and to act immediately in the event of exceedances. The permit issued under the BImSchG additionally defines plant-specific conditions that may go beyond the general regulatory values.
How does continuous emission measurement work during ongoing operations?
Continuous emission measurement is carried out by permanently installed automatic measuring equipment (AME) built directly into the exhaust gas stream of the stack. These systems capture in real time the concentrations of relevant pollutants such as CO, NOx, SO2, HCl, dust, and organic compounds, as well as operating parameters such as temperature, volumetric flow, and oxygen content.
The measured values are continuously recorded and automatically processed into half-hourly and daily mean values. If a measured value exceeds a defined threshold, the system triggers an alarm that immediately notifies the operating personnel. The measuring instruments must be regularly calibrated and maintained to ensure measurement accuracy. Approved measuring equipment must also comply with the requirements of DIN EN 14181, which governs quality assurance measures for automatic measuring equipment at stationary sources.
What is the difference between continuous and discontinuous emission measurement?
The key difference lies in the measurement frequency and purpose. Continuous emission measurement runs permanently and automatically to monitor operations in real time. Discontinuous measurement is carried out at defined intervals by external, accredited measurement institutes and serves to independently verify plant values as well as to measure pollutants that cannot be captured continuously.
Pollutants such as PCDD/PCDF, heavy metals, and certain organic compounds cannot technically be captured using automatic continuous measurement devices. For these parameters, the 17th BImSchV requires discontinuous measurements, which must generally take place at least twice a year. The measurements are conducted by state-recognized bodies in accordance with established standards, and the results must be submitted to the competent authority. Continuous and discontinuous measurements thus complement each other to form a complete monitoring system.
What happens when emission limit values are exceeded?
In the event of a limit value exceedance, operators of a thermal soil treatment plant are legally obligated to immediately adjust plant operations or, in the event of repeated exceedances, to shut them down. Short-term exceedances detected by the automatic measuring system typically trigger an immediate operational response, such as adjusting burner output, exhaust gas cleaning, or material feed rate.
If an exceedance persists or cannot be remedied immediately, plant operations must be halted until the cause has been eliminated. At the same time, there is a reporting obligation to the competent supervisory authority. This authority may impose additional conditions or order an inspection of the plant. Repeated or serious exceedances can lead to regulatory measures up to and including revocation of the operating permit. A functioning quality management system is therefore essential for detecting limit value exceedances at an early stage and systematically preventing them.
How are measurement data documented and reported to authorities?
All emission measurement data must be documented without gaps and retained for a legally prescribed period. Continuously recorded values are automatically stored in an emission register, from which annual reports are generated. These annual reports must be submitted to the competent immission control authority within the required deadlines.
In addition to the annual reports, operators must immediately report special events such as limit value exceedances or plant failures. The results of discontinuous measurements by external testing institutes are also compiled into reports and submitted to the authorities. In many German federal states, operators are additionally required to enter their emission data into the European Pollutant Release and Transfer Register (E-PRTR) if certain quantity thresholds are exceeded. The documentation obligations serve to ensure transparency toward authorities and the public and are a central element of regulatory immission control.
How ARE Deutzen implements emission monitoring in practice
ARE Deutzen has been operating a thermal soil treatment plant at the Deutzen site in western Saxony since 1994 and has more than 30 years of experience in operating a plant in compliance with BImSchG permit requirements. Emission monitoring is an integral part of plant operations and encompasses:
- Continuous emission measurement for all relevant key parameters during ongoing rotary kiln operations
- Regular discontinuous measurements by accredited external testing institutes, in particular for PCDD/PCDF, heavy metals, and other special parameters
- Multi-stage exhaust gas cleaning with dust removal, thermal post-combustion, flue gas scrubbing, and activated carbon filtration to ensure reliable compliance with limit values
- Comprehensive documentation and timely reporting to the competent authorities
- Certification to ISO 14001 (environmental management) and ISO 9001 (quality management) as the foundation for systematically controlled operations
If you would like to dispose of contaminated soil or mineral waste safely and in compliance with the law, please get in touch with us. Our experts will advise you on acceptance conditions, waste characterization, and the next steps. Contact us now and find out how ARE Deutzen can reliably support your remediation project.