What Is the Difference Between Thermal Soil Treatment and Hazardous Waste Incineration?

Thermal soil treatment and hazardous waste incineration are two fundamentally different processes: in thermal desorption, contaminants are driven out of the soil and subsequently destroyed in an afterburner, while the mineral soil fraction is preserved. Hazardous waste incineration, by contrast, destroys the entire material — contaminant and carrier matrix together. The decisive difference lies in whether the soil is recovered as a reusable material or completely eliminated. The following sections shed light on the most important questions surrounding both processes.

How does thermal desorption compare to incineration?

Thermal desorption physically separates contaminants from the soil material by heating the contaminated soil in a rotary kiln at temperatures of up to approximately 600 °C under oxygen exclusion. The contaminants evaporate or are destroyed, while the mineral soil fraction remains largely intact. Hazardous waste incineration, on the other hand, operates at significantly higher temperatures with an oxygen supply, so that the entire material is oxidized and destroyed.

Oxygen exclusion is the central feature of thermal desorption. It prevents uncontrolled combustion of the soil material and allows the released contaminants to be treated in a targeted manner in the downstream exhaust gas treatment system. This typically includes dust removal, thermal afterburning, flue gas scrubbing, and activated carbon filters to reliably comply with statutory emission limit values.

In hazardous waste incineration, the complete destruction of the waste is the primary objective. This process generates combustion residues such as slags and ashes that must be disposed of separately. No reusable soil materials are produced, which is a significant difference from thermal soil treatment from both an ecological and an economic perspective.

Which contaminants can thermal soil treatment remove?

Thermal soil treatment is suitable for a wide range of organic and inorganic contaminants. Approved substances include, among others, 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 numerous other chlorinated hydrocarbon compounds. Mercury (Hg) can also be treated at the facility.

The effectiveness of the process is based on the fact that organic contaminants are either completely destroyed or converted to the gaseous state at the temperatures used, where they are subsequently rendered harmless in the multi-stage exhaust gas treatment system. Heavy metals such as mercury evaporate and are separated in the gas phase.

Particularly relevant is the suitability for mixed contaminations — that is, soils simultaneously affected by multiple contaminant groups. Especially at complex contaminated sites where various pollutants are present side by side, thermal desorption offers a clear advantage over processes that target only individual contaminant classes.

What happens to the soil after thermal treatment?

After thermal treatment, a contaminant-free mineral material is produced that can be reused as a construction material or fill material. Although the soil loses its biological activity through the process, the mineral substance is preserved and generally meets the requirements for use in earthworks and road construction.

The quality of the treated material is verified through sampling and analysis. Only once the statutory limit values for the respective recovery class are met is the material released. This verification is an essential component of the treatment process and ensures that the material can be safely and legally returned to the material cycle.

As part of material flow management, the treatment can be integrated into a more comprehensive logistics framework that coordinates the delivery, interim storage, treatment, and recovery or disposal of materials. This significantly reduces the organizational effort for clients.

When is hazardous waste incineration the better choice?

Hazardous waste incineration is the appropriate method when the contaminated material is not mineral in nature, when contaminant concentrations are extremely high, or when organic wastes such as solvents, waste oils, or filter cakes must be disposed of that are not suitable for desorption. Incineration can also be appropriate when recovery of the soil material is not the objective.

Another criterion is the composition of the waste: materials with a high calorific value — that is, those that can themselves serve as energy carriers — are often treated more efficiently in hazardous waste incineration plants than in desorption plants. Liquid hazardous wastes, sludges with a high organic content, or heavily halogenated compounds in a non-mineral matrix are typical applications for incineration.

For mineral wastes such as soil, construction debris, or slags, thermal desorption is generally the more economical and resource-efficient choice, since the carrier material can be reused after treatment and does not need to be landfilled as a combustion residue.

Which permits apply to thermal soil treatment facilities?

Thermal soil treatment facilities in Germany are subject to the Federal Immission Control Act (BImSchG) and require an immission control permit. This regulates, among other things, permissible emission limit values, the operation of the exhaust gas treatment system, and the approved waste types and quantities. In addition, operators must be recognized as a certified waste management company (EfB) in accordance with Section 52 of the Circular Economy Act (KrWG).

Quality management systems in accordance with ISO 9001, environmental management systems in accordance with ISO 14001, and energy management systems in accordance with ISO 50001 are established certifications in the industry that go beyond the statutory minimum requirements and document operational quality. For clients, these certifications are an important criterion when selecting a suitable waste management partner.

The permit also specifies which contaminant classes may be treated at the facility. Not every facility is approved for all types of contamination. It is therefore important to verify before commissioning whether the specific contaminants in the waste stream are covered by the respective facility. Information on quality management and the relevant certifications helps to assess the suitability of a facility.

Which remediation projects are suitable for thermal soil treatment?

Thermal soil treatment is particularly suitable for the remediation of sites with complex organic contaminations in mineral materials. Typical applications include decommissioned industrial and gasworks sites, former chemical plants, military properties, and areas where mineral oil products, tar, or chlorinated solvents have penetrated the soil.

Dredged material from contaminated bodies of water, construction debris from contaminated demolition sites, and process residues such as slags, ashes, and dusts can also be thermally treated depending on their composition. The decisive factor is that the contaminant is bound to a mineral carrier material and can be driven out or destroyed by heat.

For civil engineering companies, project developers, and industrial clients wishing to revitalize contaminated sites, thermal desorption is often the most economical solution: the treated material can be used as a construction material on-site or elsewhere, saving landfill costs and reducing resource consumption. This advantage becomes particularly evident with large excavation volumes, such as those arising from infrastructure projects or industrial site developments.

How ARE Deutzen GmbH helps with thermal soil treatment

ARE Deutzen GmbH has been operating one of the most powerful thermal soil treatment facilities in Germany since 1994. With more than 30 years of experience and over 2.5 million tonnes of treated mineral materials, ARE Deutzen offers a reliable and technically mature solution for demanding remediation projects. The range of services includes:

Thermal desorption of contaminated soils, construction debris, and mineral wastes in a rotary kiln at temperatures of up to approximately 600 °C, depending on material composition and contaminant load, under oxygen exclusion
Treatment of a wide range of contaminants, including TPH, PAH, PCB, PFAS, dioxins, cyanides, mercury, and chlorinated hydrocarbons
Multi-stage exhaust gas treatment to reliably comply with all statutory emission limit values
Complete material flow management from delivery and interim storage through to recovery or disposal of the treated materials
Certified waste management company in accordance with KrWG with permits under BImSchG and certifications in accordance with ISO 9001, 14001, and 50001
Individual consulting and project support for civil engineering companies and industrial clients

If you are planning a remediation project or need to properly dispose of contaminated soils and mineral wastes, contact ARE Deutzen directly. On the contact persons page you will find the right contact for your inquiry.