Thermal soil treatment should be considered in remediation planning as soon as contamination with organic or mercury-containing pollutants is present that cannot be completely eliminated by in-situ methods. The process is particularly useful when high pollutant concentrations, complex pollutant mixtures, or tight schedules require reliable and complete cleanup. The following questions clarify when and for which projects thermal desorption is the right choice.
Which pollutants is thermal soil treatment suitable for?
Thermal soil treatment is suitable for all volatile and semi-volatile organic pollutants as well as mercury. These include mineral oil hydrocarbons (TPH), BTEX compounds, phenols, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), PFAS and PFOS, dioxins and furans (PCDD/PCDF), cyanides, nitroaromatics, and a wide range of other chlorinated hydrocarbon compounds.
The process is based on thermal desorption: the contaminated soil is heated in a rotary kiln at temperatures of up to approximately 600 °C, depending on the material and pollutant load, under exclusion of oxygen. Pollutants are either directly destroyed or converted into the gaseous state and subsequently rendered harmless in a multi-stage exhaust gas treatment system. The treatment is particularly suitable for soils with complex pollutant mixtures where multiple substance classes are present simultaneously.
The process is not suitable, however, for purely inorganic heavy metal contaminations such as lead, arsenic, or cadmium, as these cannot be destroyed by heat and cannot be volatilized. The exception is mercury, which can be thermally driven off due to its low boiling point.
When does in-situ remediation reach its limits?
In-situ remediation methods reach their limits when pollutants are present in high concentrations, difficult-to-access soil layers are contaminated, or the timeframe for biological or chemical treatment is insufficient. In such cases, thermal desorption offers a reliable alternative.
Specific situations in which in-situ methods frequently fail:
- Very high pollutant concentrations that inhibit biological microorganisms or overwhelm chemical reactions
- Heterogeneous soil stratification with varying permeabilities that prevent uniform treatment
- Persistent pollutants such as PCB or PFAS that are barely biodegradable
- Dense development or ongoing operations on the site that restrict in-situ measures spatially or temporally
- Regulatory requirements with clearly defined remediation deadlines that in-situ methods cannot meet on time
While biological methods require months or years, thermal soil treatment typically delivers demonstrably cleaned materials within a few weeks. This makes it particularly attractive when properties need to be usable again quickly.
From what quantity of contamination does thermal desorption become worthwhile?
Thermal desorption is generally worthwhile starting from quantities of several hundred tons of contaminated soil. However, the economic threshold depends less on the absolute quantity than on the type of pollutant, the concentration, and the available alternatives. For highly concentrated or persistent pollutants, the process can be the most cost-effective solution even for smaller quantities.
The following factors are decisive for the cost-benefit assessment:
- Landfill costs: For pollutants that require disposal at hazardous waste landfills, thermal treatment can be more cost-effective than landfilling.
- Transport effort: Short transport distances to the treatment facility significantly improve cost-effectiveness.
- Reusability: Thermally treated soil can be reused as a construction material after verification of baseline values, saving material costs.
- Pollutant complexity: The more persistent and regulated the pollutant, the more the advantages of thermal treatment outweigh those of alternative methods.
An early quantity and cost estimate based on soil and pollutant analyses is therefore an important first step in remediation planning.
Which project types are particularly suited to thermal soil treatment?
Brownfield projects at decommissioned industrial and gasworks sites, military properties, and former chemical plants are particularly well suited to thermal soil treatment. These sites typically exhibit complex pollutant mixtures that require reliable and complete cleanup.
Typical project types at a glance:
- Decommissioned gasworks: Soils are frequently contaminated with PAH, BTEX, phenols, and cyanides.
- Former industrial sites: Contamination by TPH, chlorinated solvents, or PCB is common.
- Military properties: Contamination by mineral oils, nitroaromatics, or explosive residues often requires thermal methods.
- Chemical plants: Complex and highly concentrated pollutant mixtures that overwhelm other methods.
- Infrastructure projects: Civil engineering projects where contaminated excavated material arises and must be disposed of quickly.
Material flow management plays a central role here: soil, dredged material, construction rubble, and process residues are systematically recorded, temporarily stored, and directed to the appropriate treatment.
When must thermal soil treatment be included in remediation planning?
Thermal soil treatment must be included in remediation planning at the latest when the investigation phase identifies pollutants that cannot be safely eliminated by in-situ methods. Ideally, the assessment takes place during the hazard evaluation phase, before remediation targets and methods are agreed upon with the authorities.
Early planning has several advantages: it enables a realistic cost estimate, secures treatment capacity, and prevents costly method changes from becoming necessary during the course of the project. Particularly for projects with tight schedules or authority-imposed deadlines, early involvement of the treatment facility is crucial.
Specific triggers for inclusion in remediation planning are:
- Detection of PAH, PCB, PFAS, dioxins, or other persistent pollutants in soil investigations
- Pollutant concentrations exceeding the limits for disposal at construction rubble landfills
- Complex pollutant mixtures that no single in-situ method can treat completely
- Revitalization projects where the property is to be put to a new use after remediation
What permits and documentation are required for thermal soil treatment?
A number of permits and documentation are required for the acceptance and treatment of contaminated soils at a thermal soil treatment facility. The facility itself must be approved under the Federal Immission Control Act (BImSchG). For the client, the documentation obligations under the Circular Economy Act are particularly relevant.
The following documents and records are typically required:
- Waste analysis: Pollutant analyses of the soil according to defined parameters that enable correct waste characterization
- Disposal certificate: For hazardous waste, an officially approved disposal certificate is required
- Consignment notes: For hazardous waste, consignment notes must be maintained in accordance with the Waste Tracking Ordinance
- Transport permit: The transport of contaminated soils is subject to the provisions of the Dangerous Goods Ordinance depending on classification
- Disposal company certificates: The certified waste management company must hold a valid EfB certification under § 52 KrWG
A certified waste management company generally assists with compiling the required documentation and handles the record-keeping. The quality management system of the disposal company ensures that all legal requirements are met.
How ARE Deutzen GmbH supports thermal soil treatment
ARE Deutzen GmbH specializes in the thermal treatment of contaminated mineral waste and has more than 30 years of experience in brownfield remediation. For civil engineering companies and industrial clients looking to remediate or revitalize contaminated sites, ARE Deutzen offers a reliable and legally compliant solution:
- Thermal desorption in a rotary kiln at temperatures of up to approximately 600 °C, depending on the material and pollutant load, for a broad spectrum of pollutants
- Acceptance of soils, dredged material, construction rubble, and mineral process residues
- Multi-stage exhaust gas treatment to ensure full compliance with all emission limit values
- Complete documentation as a certified waste management company (EfB) under § 52 KrWG
- Permits under BImSchG as well as certifications to ISO 9001, 14001, 50001, and 18001
- Individual consulting on remediation planning and method selection
If you would like to assess whether thermal soil treatment is the right solution for your project, speak directly with the experts at ARE Deutzen. Get in touch and describe your project. ARE Deutzen will advise you objectively and with a focus on practical solutions.