Phytoremediation or green remediation refers to the use of plants to treat environmental problems. It does not require excavation or removal of contaminated soil and is very low impact environmentally.
Phytoremediation is based around the use of hyperaccumulators. These plants draw heavy metals and other toxic materials out of the soil through their roots and into their leaves. The plants are then harvested and removed from the site, taking the metals with them. In some cases, valuable materials which are toxic in soil at high concentrations, like zinc, can be extracted from the plants and sold at the going rate. This process is called phytomining.
In addition to its environmental benefits, phytoremediation is extremely cost effective. In other words, it's cheap. For each acre of contaminated soil, it’s estimated phytoremediation will cost $250 to $1000. Traditional remediation runs around $1 million dollars an acre.
So why is this not a more common practice? For one thing, not all metals can be treated through phytoremediation. Lead, for example, which is a problem on the town site of the Ute Ulay, cannot be treated this way as far as science knows (although plants can be used as a sort of barrier to trap lead in by preventing erosion). Another reason may be that phytoremediation is an ongoing process and can take several growing seasons to bring soil toxins down to an acceptable level. Traditional remediation is generally a once and done deal that involves a combination of capping and relocating contaminated soil. But to compare, the tailings piles from the Ute Ulay (adjacent to the site on public land) remediated by the Bureau of Land Management a few years ago cost about $1 million dollars. It took ten years and a lot of work to raise that much money. If it had taken ten years to remediate the land using plants, the results might have been similar for a markedly smaller amount of money.
There are other considerations with phytoremediation including making sure that the metal-laden plants are not going to be problematic for wildlife (fences can do wonders in this department) and that respiration doesn't turn a ground problem into an air problem. Additionally, amendments of some kind must generally be added to disturbed soil to make it suitable for new plant life. At least one promising experiment done using pulp from paper plants has shown that what is normally an industrial waste can become a food source for bioremediating plants.
Artist Mel Chin, working with scientists like Rufus Chaney currently of the USDA, brought broader attention to this process through his piece Revival Field (1990-present) and while scientists continue to experiment with it, phytoremediation is a nascent technology in many ways.
Stay tuned for another blog post about alpine pennycress, a Rocky Mountain weed and hyperaccumulator extraordinaire.