A stationary soil treatment plant is more practical than a mobile unit when large quantities of waste arise, complex contaminant mixtures are present, or high emission control requirements must be met. Mobile units, by contrast, are suitable for smaller, spatially isolated contaminations involving comparatively straightforward pollutants. The following sections examine the decisive criteria in detail.
What factors determine the choice between stationary and mobile treatment?
The choice between stationary soil treatment and a mobile unit depends on four central factors: the type of contaminant and complexity of contamination, the volume of waste generated, the regulatory framework, and the requirements for exhaust gas purification. None of these factors stands alone; each must be assessed in the overall context of the remediation project.
Projects with heterogeneous contaminant profiles, high throughput volumes, or strict emission requirements clearly favor a stationary solution. Where a spatially confined site with a manageable range of contaminants is involved, a mobile unit may be more economically attractive. The decision should always be based on a thorough waste characterization.
What are the advantages of a stationary plant over a mobile one?
Stationary plants offer decisive technical advantages over mobile units: they feature multi-stage exhaust gas purification systems, higher and more stable process temperatures, and significantly greater capacity. This enables them to treat even complex contaminant mixtures safely and completely.
Specifically, stationary soil treatment plants offer the following strengths:
- Greater process safety: Stable temperature conditions throughout the entire treatment period ensure reliable contaminant destruction.
- Multi-stage exhaust gas purification: Dust removal, thermal post-combustion, flue gas scrubbing, and activated carbon filters ensure compliance with statutory emission limit values.
- Wider range of materials: In addition to soil, construction rubble, sludges, ashes, and other mineral waste can also be treated.
- Higher throughput capacity: Large-scale projects involving several tens of thousands of tonnes of material can be handled economically and efficiently.
- Long-term operational experience: Stationary plants accumulate decades of technical know-how that feeds into every individual treatment assignment.
For demanding brownfield remediation projects where quality and legal certainty are paramount, the stationary plant is generally the superior choice. More information on how thermal treatment in a rotary kiln works can be found in the relevant service area.
When is a mobile unit the better choice?
A mobile unit is the better choice when transporting material to the site of a stationary plant is disproportionately expensive or logistically impractical, the level of contamination is comparatively low, and the quantity of material to be treated is in the lower range.
Typical scenarios for the use of mobile units include:
- Remote sites where long transport routes would significantly increase overall costs
- Contamination with mineral oil hydrocarbons (TPH) at low to medium concentrations
- Remediation projects involving a material volume of a few hundred to several thousand tonnes
- Projects with short time windows requiring rapid on-site mobilization
An important caveat: mobile units quickly reach their limits when dealing with complex contaminants or high emission requirements. Their exhaust gas purification is generally less comprehensive than that of a stationary plant, which restricts their approval for certain contaminant classes.
Which contaminants necessarily require stationary treatment?
Contaminants such as PCDD/PCDF (dioxins and furans), PCB, PFAS/PFOS, mercury (Hg), cyanides, and nitroaromatics generally require stationary thermal desorption. These compounds place particularly high demands on process temperature, residence time, and exhaust gas purification that mobile units are technically unable to meet.
The reason lies in the chemistry of these substances: chlorinated hydrocarbon compounds, dioxins, and persistent organic pollutants must be treated at precisely controlled temperatures and under oxygen exclusion so that they are completely destroyed without forming hazardous reaction products. Thermal post-combustion of the resulting exhaust gases at temperatures above 850 °C is mandatory, something mobile units are rarely able to achieve.
Mercury also requires special care: during thermal desorption it is converted to a gaseous state and must subsequently be safely separated in specialized exhaust gas purification stages. For all these contaminant groups, stationary soil treatment is not merely recommended but, for legal and safety reasons, is frequently the only permissible option.
How does the quantity of waste affect the choice of plant?
The quantity of waste is a key economic criterion when choosing between a stationary and a mobile plant. From approximately 5,000 to 10,000 tonnes of contaminated material upward, a stationary soil treatment plant is generally more economically advantageous, as transport costs are offset by economies of scale in treatment.
For smaller quantities, mobilizing a stationary plant — that is, the effort involved in delivery, storage, and process control — can be relatively higher than using a mobile unit on site. Nevertheless, the pure quantity threshold should not be viewed in isolation: if the contaminant requires stationary treatment, that remains the only permissible option even for smaller quantities.
For projects with large material volumes and heterogeneous composition, structured material flow management provides additional planning certainty by directing material streams to the most appropriate treatment processes.
What are the regulatory differences between stationary and mobile plants?
Stationary soil treatment plants are subject to the Federal Immission Control Act (BImSchG) and require a comprehensive immission control permit. Mobile units are generally approved under water law or simplified building permit procedures, which allows faster commissioning but also means narrower limits on the permissible range of contaminants.
Specifically, the approval frameworks differ in the following respects:
- Emission limit values: Stationary plants under BImSchG must comply with strict, continuously monitored emission limit values. Mobile units are subject to less comprehensive measurement requirements.
- Permissible waste types: The scope of approval for stationary plants generally allows a significantly broader range of waste codes and contaminant classes.
- Site permit: Mobile units require a separate permit or notification for each new deployment site, which increases the administrative burden when multiple sites are involved.
- Quality certifications: Stationary plants are frequently certified to ISO 9001, 14001, and other standards, providing clients with a reliable quality basis.
For clients from industry and civil engineering, this means: anyone who needs legally secure disposal documentation and works with complex contaminant mixtures is on safe ground with a stationary plant approved under BImSchG. Information on quality management shows which standards are upheld in this regard.
How ARE Deutzen helps in choosing the right treatment method
ARE Deutzen GmbH has operated a stationary thermal soil treatment plant in Deutzen, western Saxony, since 1994, and has treated more than 2.5 million tonnes of contaminated mineral materials during that time. As a certified waste management company under BImSchG, ARE Deutzen offers civil engineering companies and industrial clients a reliable, permit-compliant solution for demanding soil remediation projects.
The range of services includes specifically:
- Thermal desorption in a rotary kiln at temperatures of up to approximately 600 °C, depending on the material and contaminant load
- Treatment of a broad range of contaminants, including PFAS/PFOS, PCB, PCDD/PCDF, Hg, PAH, BTEX, and cyanides
- Multi-stage exhaust gas purification with thermal post-combustion and activated carbon filters
- Material flow management for soils, dredged material, construction rubble, and process residues
- Interim storage and mechanical-physical pre-treatment on site
If you are faced with the question of whether stationary or mobile treatment is the right choice for your project, the experts at ARE Deutzen will advise you based on your specific waste characteristics and project requirements. Get in touch now and receive a well-founded assessment for your remediation project.