Fungi can clean polluted soil

A Finnish researcher has found that fungi can be harnessed to clean polluted soil which cannot be cleaned using traditional composting.

Erika Winquist, of Aalto University, explained that soil that has been polluted by organic pollutants such as oils can be treated by composting; however, this is not effective against many other organic pollutants such as polyaromatic hydrocarbons and dioxins. The compounds are found in areas where sawing is carried out and where there is distribution of fuels, waste treatment and various kinds of industry.

In Finland during 2005 and 2006, almost 3 million tonnes of excavated, contaminated soil was transported into landfill sites and other treatment plants. A more sustainable practice would be to clean the polluted soil, but putting it into landfill is easy and cheap, and other methods have limited use. For example, burning the soil in an incinerator destroys the organic pollutants, but the process is expensive and there is insufficient incineration capacity in Finland to treat all the soil.

However, said Winquist, fungi could be used to expand bioremediation for the destruction of the more enduring organic pollutants. Winquist grew fungi on pine bark (a good growing medium for fungi) over four to six weeks. The fungi were then taken to a treatment plant, where the mycelia of white rot fungi were allowed to grow in the polluted soil.

Image shows how the fungus growing on the bark is placed into the soil in layers. Image credit: Aalto University.

White rot fungi grow naturally on wood. As they grow in the soil, they break down the compounds with lignin-like structures that pollute it. The soils examined were from old sawmill sites that were contaminated with polyaromatic hydrocarbons (PAH compounds) and dioxins. In laboratory-scale tests, the best results showed 96% of PAH compounds and 64% of the dioxins were broken down in three months.

Image shows how the fungus grows in the soil and on the surface. Image credit: Aalto University.

The research was carried out in cooperation with the University of Helsinki and the Finnish Environment Institute. Funding was provided through the Symbio program run by Tekes, the Finnish Funding Agency for Technology and Innovation, as well as by the companies working with the program. Research into the environmental applications of fungi continues to be carried out at the University of Helsinki, and Ekokem Oy, one of the companies involved in the research, has acquired the rights to the cleansing method.

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