Thermal desorption can be a viable alternative to hazardous waste incineration when dealing with mineral-bound contaminants that can be separated from the carrier material through heat treatment under oxygen exclusion. The decisive advantage: the soil material is preserved and can often be reused after treatment — something hazardous waste incineration cannot achieve. The following sections examine the technical differences, suitable waste types, and regulatory requirements in detail.
Which contaminants can be treated by thermal desorption?
Thermal desorption is suitable for a wide range of organic contaminants in mineral waste. Materials that can be treated include mineral oil hydrocarbons (MKW), BTEX compounds, phenols, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), PFAS and PFOS, dioxins and furans (PCDD/PCDF), cyanides, nitroaromatics, and numerous other chlorinated hydrocarbon compounds. Mercury (Hg) can also be driven out of soil material through thermal treatment.
The effectiveness of the process is based on the fact that these compounds are either destroyed or converted to a gaseous state at defined temperatures. In the rotary kiln, the material is heated to temperatures of up to approximately 600 °C, depending on the material and contaminant load. The resulting pollutant gases are then treated in a multi-stage exhaust gas purification system that includes dust removal, thermal post-combustion, flue gas scrubbing, and activated carbon filters.
Typical areas of application include contaminated soils from decommissioned industrial and gasworks sites, as well as contamination from former military or chemical facilities. The process is particularly effective in cases of mixed contamination, where multiple groups of pollutants occur simultaneously.
How do thermal desorption and hazardous waste incineration differ technically?
The fundamental difference lies in the treatment objective and process management. In hazardous waste incineration, the entire waste material is completely combusted at very high temperatures, destroying organic substances and leaving inorganic residues as slag or ash. Thermal desorption, by contrast, operates under oxygen exclusion and at significantly lower temperatures in order to separate contaminants from the carrier material without burning the material itself.
Specifically, this means:
- Thermal desorption: Treatment temperatures of up to approximately 600 °C depending on material and contaminant load, oxygen exclusion, preservation of the mineral carrier material, separate exhaust gas purification
- Hazardous waste incineration: Temperatures of 850 °C and above, oxidative combustion, complete destruction of the organic fraction, residues in the form of slag and ash
This leads to another significant difference: the volume of residual materials requiring disposal. With thermal desorption, the majority of the source material remains as treated soil that can be reused. Hazardous waste incineration, by contrast, produces combustion residues that must themselves be disposed of. For mineral waste containing organic contaminants, thermal desorption is therefore often the more technically and economically efficient solution.
When should thermal desorption be preferred over hazardous waste incineration?
Thermal desorption should be preferred over hazardous waste incineration when the waste is predominantly mineral in nature and the contaminants are organic. This applies in particular when the treated material is intended to be reused as a construction material or backfill after desorption, since hazardous waste incineration does not offer this option.
Further criteria that favor thermal desorption:
- High mineral content: Soils, construction rubble, and dredged material with low organic content are particularly well suited.
- Organic contaminants: Compounds such as MKW, PAH, PCB, or PFAS can be effectively separated from the solid material through desorption.
- Recovery objective: When the source material is intended to be made reusable after treatment, desorption is the logical choice.
- Cost efficiency for large quantities: For large-scale remediation projects, thermal soil treatment can be more economical than incinerating large volumes of waste.
- Avoiding landfill capacity: Treated material generally does not need to be landfilled, which reduces disposal costs and transportation effort.
Hazardous waste incineration remains the right choice when the waste has a high organic or calorific content, when inorganic contaminants predominate, or when the material is fundamentally not recoverable. Waste suitable for thermal soil treatment can be reliably identified in advance through laboratory analyses and characterization.
Which waste types are not suitable for thermal desorption?
Waste types not suitable for thermal desorption include those whose contaminants are non-volatile or cannot be separated from the solid material by heat. This includes in particular waste with high concentrations of inorganic contaminants such as heavy metals (with the exception of mercury), which cannot be removed by thermal treatment but can at most be redistributed.
Further unsuitable waste types include:
- Waste with a very high organic content or high calorific value that would combust uncontrollably in the rotary kiln
- Heavily water-saturated sludges that must first be mechanically pre-treated or dried before thermal treatment is viable
- Waste containing contaminants that are only destroyed at temperatures above the treatment range
- Radioactively contaminated materials, which are subject to special statutory regulations
In cases of doubt, waste characterization through laboratory analyses clarifies whether a material is suitable for thermal desorption. As part of a comprehensive material flow management approach, a combination of mechanical-physical pre-treatment and thermal treatment may also be appropriate.
What happens to the material after thermal desorption?
After thermal desorption, a mineral solid remains that is free of the treated organic contaminants. Whether this material can be recovered or must be landfilled depends on its composition and the applicable quality requirements. In many cases, it can be reused as a construction material, backfill, or for earthworks.
The decision on the further path of the treated material is based on eluate analyses and solid-matter tests carried out after treatment. If the material meets the limit values of the relevant regulatory frameworks, there is nothing to prevent its recovery. In this way, thermal desorption makes a concrete contribution to resource conservation: mineral material that would otherwise have to be landfilled is returned to the material cycle.
The exhaust gases generated during treatment are processed in a multi-stage exhaust gas purification system. Dusts, condensates, and other process residues are collected separately and disposed of or recovered in accordance with their characteristics. The process is designed to reliably comply with statutory emission limit values.
Which permits and documentation are required for thermal desorption?
Thermal desorption facilities require a permit under the Federal Immission Control Act (BImSchG). Operators must demonstrate that their facility complies with the emission limit values of the 17th BImSchV and has a functioning exhaust gas purification system. In addition, certification as a specialist waste management company (EfB) pursuant to Section 56 of the Circular Economy Act (KrWG) is an essential quality credential.
The following documentation and certifications are relevant for clients:
- BImSchG permit: Basic prerequisite for operating the facility
- Specialist waste management company (EfB): Confirms proper and harmless disposal
- ISO 9001: Quality management system
- ISO 14001: Environmental management system
- ISO 50001: Energy management system
- Waste law documentation: Consignment notes, acceptance certificates, and disposal records in accordance with the Waste Records Ordinance
Clients should also ensure that the facility is approved for the specific contaminant groups present in their waste. Not every facility holds a permit for all contaminant classes. A reputable operator will transparently provide the relevant permits and certificates and will assist with the correct waste law declaration. Further information on quality management provides insight into the standards a certified operator must meet.
How ARE Deutzen GmbH supports thermal soil treatment
ARE Deutzen GmbH specializes in the thermal treatment of contaminated mineral waste and has been operating one of the most powerful thermal desorption facilities in Germany since 1994. The company offers a complete solution for civil engineering firms, remediation planners, and industrial clients seeking to treat contaminated sites safely and in full compliance with the law.
The range of services specifically includes:
- Thermal treatment of soils, construction rubble, and mineral waste containing MKW, PAH, PCB, PFAS, dioxins, cyanides, mercury, and other contaminants
- Multi-stage exhaust gas purification to ensure reliable compliance with statutory emission limit values
- Waste characterization and advisory services for the correct classification of materials
- Complete waste law documentation and record-keeping
- Acceptance of process residues such as slags, ashes, sludges, and dusts
- Interim storage and mechanical-physical pre-treatment as supplementary services
With over 30 years of experience, more than 2.5 million treated tonnes, and all relevant certifications, ARE Deutzen is a reliable partner for demanding remediation projects. Get in touch and discuss with the specialists whether thermal desorption is the right solution for your project.