From: Public Services and Procurement Canada
Mycoremediation is an aerobic bioremediation technique that uses white rot fungus (Phanerochaete chrysosporium, Trametes versicolor, etc.) as an inoculum for ex situ or in situ treatment of residual organic compound contamination in soil. White rot fungus produces extracellular enzymes, such as peroxidases and lactases, to degrade lignin. These enzymes are able to catalyze the degradative attack on a variety of organic contaminants such as pesticides, conventional explosives, semi-volatile organic compounds (SVOCs) and other recalcitrant contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and pentachlorophenol (PCP). Metals are not degraded by enzymes but accumulate in the fungi fruiting bodies.
This technique consists of mixing contaminated soils with the white rot fungus and a substrate, such as woodchips, to stimulate the development of the fungus and to promote soil aeration. This technique can be used with biopiles, phytoremediation, co-composting or land farming. Several factors affect the performance of this technique including, nitrogen and oxygen concentrations, pH, humidity and temperature.
As mentioned, mycoremediation is not a stand-alone remediation technique but a variant of bioremediation. White rot fungus can be used as an inoculum, for example, in ex situ biopiles or with other bioremediation technologies such as bioventing. While the use of fungi in biopiles has been documented, the in situ application is not widely used commercially and is studied in many universities and research centers.
Fungi is often indigenous to the soils and they are stimulated through the provision of the appropriate growth conditions. Alternatively, non-indigenous fungal strains can be added to the soil (bioaugmentation). In Canada, the introduction of microbial strains into the environment is regulated under the New Substances Notification Regulations (NSNR) of the Canadian Environment Protection Act (1999). Microorganisms must be on the Domestic Substances List (DSL) compiled by Environment Canada in order to be used in remediation procedures.
The application of fungus as part of bioremediation remains largely in the laboratory and pilot scale phase. Few practitioners can comment on the implementation of mycoremediation on-site. The implementation of mycoremediation will depend on the type of bioremediation technology which it is used. This can include both ex situ (biopiles, composting, phytoremediation, etc.) or in situ (aerobic bioremediation) technologies. Please see the individual fact sheets for more details on implementation of these technologies. Laboratory and/or pilot scale preliminary testing could be required. Indigenous white rot fungus can be extracted from the contaminated soils and multiplied in laboratory conditions to produce an inoculum to be re-injected, ideally using site-specific conditions and in presence of site-specific contamination.
The addition of fertilizer, pH adjustment and/or soil texture additives are often required as part of the treatment. As any bioremediation technology, treatment systems will include some sort of measures to control moisture, aeration, nutrients and sometimes temperature. However, compared to other bioremediation techniques more emphasis is often put on moisture control systems since it is a more sensitive parameter for mycoremediation. If soil contaminants include volatile compounds, vapour/off-gas controls may be required. Depending on soil moisture content and contaminant characteristics, leachate collection and treatment may also be required.
Modest amounts of fertilizer and soil texture additives can be kept on-site. For example, peat moss could be used to increase permeability and moisture retention of the soil matrix. Inorganic nutrients could be added to irrigation water over time. Storage will depend on the complementary bioremediation technique which it is coupled with.
For ex situ treatment with biopiles, landfarming or composting, treatment cells are aerated by tilling/mixing or with ventilation pipes. They may warm up as a function of exothermic reactions or may be heated via other intensive methods and as a result, off-gassing could be expected. If contaminants pose an unacceptable risk, the treatment system will normally include vapour collection with a treatment before being rejected into the environment. If treatment is successful, the primary residual is fungal biomass (which decays over time). Excess reagent typically cannot be recovered, and is generally consumed.
Remote sites are prone to high mobilization and on-site monitoring costs, limited equipment availability and short work windows. Difficulties in procuring timely analytical results may necessitate reliance on field screening, staged interventions and/or risk management. Biotreatment methods are popular options in remote areas but must be designed to operate without operator intervention for long periods.
Cooler temperatures (below 10 °C) significantly impair biodegradation using fungi. Soils may be heated and/or insulated, for example, using electrical heat-trace and expanded polystyrene (EPS) panels.
Notes:
Metals are not degraded by this technology but accumulate in the fruiting bodies and should be collected regularly.
No monitoring is required for ex situ nor in situ treatment, since this technology doesn’t affect soil properties and structure.
By-product and metabolite production during biodegradation or transformation with white rot fungus need to be analyzed to ensure that no production of compounds of greater concern than the parent compound are produced.
Using fungi as part of a biological treatment doesn’t require any additional secondary treatments. However, depending on the type of contaminants and treatment conditions, a vapour collection may be required.
Application examples are available at this address:
Literature provides a lot of different results about the performances of white rot fungus. Efficiency depends widely on the type of soils, contamination and complementary technology.
It is important to verify whether white rot fungus technology meets the remediation objectives before applying this technique to a large volume of soil.
Mycroremediation is a variant of bioremediation and is applied as part of other technologies, such as biopiles, composting, phytoremediation, or in situ aerobic bioremediation. Please see the individual fact sheets for more details measures to improve the sustainability of the technology.
Unavailable for this fact sheet
Composed by : Magalie Turgeon, National Research Council
Updated by : Jennifer Holdner, M.Sc., Public Works Government Services Canada
Updated Date : March 1, 2015
Latest update provided by : Marianne Brien, P.Eng., Christian Gosselin, P.Eng., M.Eng., Golder Associés Ltée
Updated Date : March 31, 2018
