White Rot Mushroom, Trametes versicolor. Photo: Luke Detwiler via Flickr.
Fungi clean contaminated soils
22nd May 2014
A new system for cleaning soils contaminated with industrial toxins harnesses the power of White rot - a common fungus that decays fallen wood in forests. Research in Finland shows it can also destroy dioxins and poly-aromatic hydrocarbons.
The breakthrough opens up new possibilities for the low-cost cleansing of contaminated soils, which are widespread on industrial and former industrial sites.
'White rot' fungi that decay dead wood in forests can be harnessed to clean soil polluted with toxic, persistent organic chemicals, which cannot be cleaned using traditional methods.
The discovery was made by Erika Winquist, a researcher at Aalto University in Finland. In trials, up to 96% of poly-aromatic hydrocarbon (PAH) compounds and 64% of the dioxins in contaminated soil were broken down after three months.
The breakthrough opens up new possibilities for the low-cost cleansing of contaminated soils, which are widespread on industrial and former industrial sites - for example coal gasification plants, sawmills, timber treatment works, waste processing centres and fuel depots.
Millions of tonnes of contaminated soils dumped
Where soils are polluted by simple organic pollutants such as oil, it is amenable to treatment by composting. However PAHs and dioxins are recalcitrant and are not broken down by these methods. Some 45% of excavated contaminated soils contain these pollutants, says Winquist.
As a result, these soils are often transported to landfill sites - Finland alone dumps over a million tonnes of contaminated soil to landfill every year.
An alternative is to burning the soil at high temperature, over 1,000C, to destroy the pollutants. But the process is expensive and highly energy intensive - and in any case few countries have sufficient incineration capacity to treat all the polluted soils.
Fungal mycelia break down soil-polluting compounds
Under Winquist's method, the White rot fungus (Trametes versicolor) is initially grown on pine bark, which naturally contains compounds that prevent the growth of other microbes, making it the ideal fingal growing medium for fungi.
After 4 to 6 weeks, the fungal culture is transferred to the contaminated soil in a temperature-controlled treatment plant where the White rot mycelia grow into the polluted soil, and break down lignins and polluting compounds with lignin-like structures, including dioxins and PAHs.
Fungi could be used to expand bioremediation for the destruction of the more enduring organic pollutants too, states Winquist.
Erika Winquist's doctoral dissertation is "The potential of ligninolytic fungi in bioremediation of contaminated soils". She received a public examination of her doctoral dissertation on 16 May 2014 at Aalto University School of Chemical Technology.
The research was carried out in cooperation with the University of Helsinki as well as with the Finnish Environment Institute. Funding was provided through the Symbio programme run by Tekes, the Finnish Funding Agency for Technology and Innovation, as well as by the companies working with the programme.
Research into the environmental applications of fungi continues to be carried out at the University of Helsinki. Ekokem Oy, one of the companies involved in the research has acquired the rights to the method of using fungi for cleansing.
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