Freezing technology removes pollution from the soil

Innovative freezing technology cleans contaminated soil both cheaper and more sustainable.

Contaminated land is not just a potential health hazard, but also an economic problem, as cleaning or tidying up a contaminated site can involve significant costs. Areas where the subsoil consists of clay are particularly complicated, as in the past it has only been possible to decontaminate these areas by warming the soil or digging it all up. In Denmark, there are about 1,500 sites like this.

Orbicon is taking part in a new research project in collaboration with Geo, GEUS and the entrepreneur, aiming at developing a technology that can overcome this challenge.

No rubbish to clear – the chemical process neutralises the contamination
The technology is called CryoRem and is in the process of changing the way that contaminated clay soil is cleaned. The technology is currently being tested in a gravel pit in Kallerup, and if tests go as expected the method will be both cheaper and more sustainable than the methods in use today. The technique involves gradually cooling and freezing the contaminated soil, which creates an environment in the frozen ground that makes it possible to convert or neutralise the contamination.

Moraine clay, which this method is used on, is very common in Denmark and in many other places in the northern hemisphere, so there is a huge potential for the technique once it is fully developed.

“The method works well in soils with the grain size distribution typically found in moraine deposited in large parts of Denmark, and in other parts of the northern hemisphere. Moraine clay is a type of soil in which it is difficult to use other methods to control the chemical reaction that can break down contamination”, explains Development Leader at Orbicon, Thomas Hauerberg Larsen.

Still at the research stage
The pilot project was conducted over a period of three years, and involved a number of calculations and laboratory tests.

It will be some years before the method is a finished product, and hopefully it will get achieve legitimacy in relation to certain types of geology and contamination in line with other methods that are used in connection with cleaning of contaminated soil.

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WSP offers engineering consulting services in the areas of environment, utilities and building design.

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Mads Sønnegaard Poulsen

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