Perhaps you’ve just brought a new piece of land and want to set up a garden, or you’ve had a fire come through your place. Both of these situations’ can be hiding lurking dangers, in the form of heavy metals and toxins. Many home gardeners are unwittingly growing their well-loved home produce in soils potentially toxic with lead from old house paint or toxins from farming practices. After the Californian fires, researchers found close to 2000 chemicals in the soil. Fires can leave behind a footprint of heavy metals, copper, lead, arsenic, asbestos, brake fluid, fire retardants and volatile organic chemicals such as benzene. Approaches to remedy these situations avoid growing in the soil at all, by either removing contaminated soil or building raised garden beds.
Mycoremediation may be one of the best tools on hand to actually deal with the issue. The mycelia of mushroom-producing fungi produce over 120 different enzymes. Incredibly powerful enzymes which can transform even the most troublesome of our wastes, such as lead, cadmium, petroleum and radiation, as well as organic pollutants in groundwater. Even the hangover from our modern world, plastic, can be broken down by oyster mushrooms.
Mycelia are the ultra-fine and dense matrix of the thread-like white hyphae that is the vegetative part of the fungi (as opposed to the sexual organs you think of as mushrooms). It is the mycelia that send out the enzymes that break down chemicals, and that also act as a filter and erosion control, among many other fantastical things.
The crucial outcome from bioremediation is the splitting of contaminants to their basic components to N2, H2O, CO2, HCl, etc. Radiation and heavy metals cannot be decomposed fully, but they can be reduced into forms which have lower solubility. This process either occurs through changes in oxidation states, rendering them less harmful in the ground, or the mushrooms draw materials into their fruiting bodies which can be physically harvested and disposed of safely.
For land remediation of heavy metals and toxins, and erosion control.
1. First lay strips of cardboard and spread a layer of woodchips 6-12 inches deep. If available add a little coffee grounds and corn cobs, banana leaves to this layer.
2. Rake out the oyster mushroom spawn
3. Then mulch the landscape with the fairly fresh woodchips to a minimum depth of 6-12 inches.
4. Cover with a inch of straw
5. Water it all in.
6. When mushrooms are fully formed, if you have heavy metals or radiation, then mushrooms must be disposed of safely.
These images are an example from a project at the New Leaf Eco Centre funded by the Land Conservancy for Southern Chester County, PA, USA.
- Fungi need lots of good quality water. Do the squeeze test, squeeze the substrate tightly in your hand: one or 2 drops of water should appear between your knuckles. Add more water if needed. Don’t drown them! Avoid chlorinated water. If you only have chlorinated, then fill drums and aerate to allow it to off-gas, or filter it using Reverse Osmosis (RO) or through humates- which the fungi will love you more for!
- Feed your fungi a healthy diet. Oyster mushrooms will grow on most carbon-based materials. These feed materials need to be fairly fresh – between 2 weeks to 2 months old. If they are too old, they will have other potential competitors, making it hard for your mushroom to grow. I prefer deciduous white wood species such as poplar, willow, birch, beech elm, cottonwoods…hardwoods, such as gum, or conifers contain anti-mircobial substances and are high in tannins, which slows fungal growth down. They can be used, but aging is preferred.
- Fungi need warmth. There are a few cold weather lovers, but most fungi like it warm, around 20 degrees C (70 degrees F). Nothing above 36 degrees C (105 degrees F. )
Extra mushroom bonus:
- Mushrooms can be added to your grey water system.
- Mycelliated straw can be used to absorb spilled oil.
- Straw bales can be inoculated with mushroom spawn, and lain in polluted runoff areas or contaminated streams.
- Alternatively, hessian/burlap sacks can be filled with straw, coffee grounds, cardboard, and mushrooms spawn, and used to catch and filter contaminated water.
By Nicole Masters.