Plants perform countless miracles, from capturing energy from the sun to power the biosphere to taking the carbon dioxide we exhale with every breath and turning it onto the oxygen we need to survive. Increasingly, humans are looking to plants and other biological organisms for their ability to clean up the toxic mess we’ve left in our wake as we’ve colonized the planet. Read on to learn more of some of the most promising bioremediation species and the pollutants that they devour.
Bioremediation can refer to the use of microbes, fungi (mycoremediation) or plants (phytoremediation) that have the ability to remove pollutants from the environment. Microbes and fungi generally accomplish this through breaking down toxic substances into benign byproducts, which is highly effective with things like petroleum products, chlorinated solvents and even radioactive substances. It is less effective with heavy metals, however, which is where plants enter the picture. In this case, the contaminants (lead, mercury, cadmium, etc.) are absorbed in the plant’s tissues, which are then removed and incinerated to recover the metals.
We may enjoy eating oyster mushrooms in omelets, but they also have another, incredibly profound quality: they enjoy eating diesel fuel and other petroleum products for breakfast. In one study, soil contaminated with diesel oil was inoculated with oyster mushroom mycelia, resulting in a 95 percent reduction of toxic compounds after a one-month period. The resulting byproducts were nothing
more than carbon dioxide and water. Other related fungal species are known to break down chemicals such as polyurethane and many common pesticides and herbicides.
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Some plants specialize in eating just one type of pollutant. This is a result of having evolved in rare terrestrial habitats where the soil is naturally high in certain compounds that would be toxic to most plants, such as the case with Rinorea niccolifera, a distant relative of violets from an island in the Philippines, where nickel levels in the soil are off the charts. Scientists are looking at this species as an agent to clean up industrial sites contaminated with nickel, but also as a non-invasive, “green” mining technique. Rinorea absorbs up to 1,000 times as much nickel as most other plants, making it theoretically possible to plant fields of it in nickel-rich soils and then extract the metal from the harvested crop. Rinorea was just discovered in a remote area last year and is now undergoing testing for it metal-eating abilities.
This group of nearly 200 rod-shaped bacteria contains a number of species with profound implications for both people and the planet as a whole. Some species cause human illnesses, while others are used to create medicine. There are species of pseudomonas that protect crops from pests and disease, and others that are used to seed clouds to create rainfall. One species of pseudomonas has been found to eat caffeine, breaking it down into carbon dioxide and ammonia. When it comes to bioremediation, however, the pseudomonas really shine: they enjoy dining on harsh petroleum products, from toluene to carbozole and carbon tetrachloride. In fact, they are the number one bacteria used to clean up oil spills.
Sugar Cane, Combined with Shrimp
Ok, sugar cane and shrimp do not clean-up pollution all by themselves, but together, they’re used to make a substrate for iron particles; one of the latest tools in the effort to clean up contaminated groundwater. A company in New Orleans is using local, sustainably farmed sugar cane and Gulf shrimp in its patented process to make a powder that dissolves chlorinated compounds on contact. These are the nasty chemicals that are used by drycleaners, as well as in the aerospace and microprocessor industries. The powder is injected into groundwater beds at contaminated sites, where it quickly permeates through microscopic soil pores to clean up the water almost instantly, making it safe for consumption in nearby communities.
These are some of the most common fern species in the world, frequently found growing on clearcut forest land and brownfields; a term for polluted urban land. Some species of bracken fern have been noted as the only species surviving at abandoned mines and other sites contaminated with extremely high levels of heavy metals, such as copper, lead, arsenic and nickel. Scientists have learned how to grow them intentionally at these contaminated sites to pump the metals out of the ground. What is particularly interesting about this approach is that the metals don’t go away— they’re just moved to the body of the plant. In some cases, the plants must then be disposed of in a special landfill for toxic waste, though there is an increasing secondary market for recycling the metals for re-use.
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