Cattail Army Deployed to Fight Water Pollution
The lowly cattail is emerging as the weapon of choice against water contamination, and perhaps even global warming. In addition to its use in large phytoremediation projects to absorb contamination from groundwater and wetlands, the cattail could also work in on a small, inexpensive scale, helping to reduce arsenic contamination in impoverished areas. All this and biofuel, too?
Cattails, Phytoremediation, and Biofuels
There is a long history behind phytoremediation, the use of plants to absorb pollutants from water. A more recent development involves harvesting the plants for biofuel production. If the contamination in question is a petroleum product, that’s a nifty sort of poetic justice. We’re not that far away from it. For example, the U.S. Air Force has been hosting a phytoremediation project for years at its base in Carswell, Texas, using poplars to absorb trichlorethelyne (TCE), a common industrial solvent. The American Society of Plant Biologists also notes that it may be possible to recover and recycle certain metals from plants grown in phytoremediation projects.
Cattails are ideal for large scale phytoremediation projects in wetlands. In an odd twist, cattails are being used to fend off other cattails in the Florida Everglades. The cattails are allowed to thrive in designated pre-treatment areas, where they absorb phosphorus from runoff. This helps keep excess phosphorus out of the Everglades, which in turn helps prevent cattails from overrunning protected areas.
Cattails, Water Pollution, and Global Warming
Phosphorus removal is just the tip of the water pollution iceberg that could be solved by cattails. Cattails have been associated with remediating sites contaminated with arsenic, pharmaceuticals, and even explosives. As for a role in the global warming picture, planting cattails could help prevent excess methane emissions from degraded wetlands.
Cattails and Backyard Water Purifiers
For impoverished areas with enough rainfall to support marsh plants like cattails, micro-scale phytoremediation could be an affordable way to help bring arsenic contamination down to safer levels. Jeremiah Jackson of the engineering firm Kleinfelder has come up with one solution. It’s a backyard cattail water purifier that requires no power or plumbing, which can be assembled from materials at hand using simple instructions. Sometimes it takes a low tech solution to solve a high tech problem.
Image: D’Arcy Norman at flickr.com.
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May 16th, 2009 at 4:17 pm
With plants absorbing all these chemicals, what happens when the plants die? Are the plants actually breaking down the chemicals or are they just temporarily storing them? Is this a real long-term solution?
May 16th, 2009 at 5:56 pm
Yes, they just store the ‘pollutants’.
I can’t understand the reference to biofuels, if the cattails were burnt for power the same pollutants would be released into the atmosphere.]
One of the basic scientific principles is that no element (in fact nothing) can be created or destroyed in the long term.
May 17th, 2009 at 6:33 am
Certainly no element can be destroyed by a non-nuclear process. However, that does not apply to molecules. It’s certainly within the realm of possibility that these plants could break down some of the chemicals. The question is whether they actually do or not?
May 17th, 2009 at 12:36 pm
There are several different things going on here. With things like arsenic or lead, it is capturing them, concentrating them, and storing them in a less active (molecular) form. You still have to sequester them for permanent removal. Practically, it is usually best to “let sleeping toxins lie”. You have immobilized them. They do not generally remoblize upon the death of the plant, the downstream water stays cleansed of them. You can generally neither burn nor eat those cattails. You may be able to make fuel gas or ethanol from them, with a residual waste in which the toxin is even further concentrated. Unprocessed, the toxins end up in the voluminous soil produced by the plant, so extract the soil(it is clogging the stream or pond), and use it for something other than growing food. If you have use for the toxin, it has been concentrated for easier access.
With things like nutrient pollution, cattail makes more cattails rather than algae blooms.
With things like insecticides and residuals from chemical warfare (very relevant in the places this is needed most) results vary and are not well known. The problem is that the breakdown products are generally toxic too.
If the water and soil they are grown in are clean, cattails are an excellent food crop and a fine source of biofuels.
Uncontrolled, they are a source of enormous troubles, ranging from desertification to flooding, with malaria and yellow fever in between. This plant is a dessication machine. It is one of the main driving forces in the expansion of the deserts. The quantity in what used to be Lake Chad is sufficient to feed every African a daily loaf of bread, if it could all be harvested, and were all fit for human consumption. It converts wetlands into drylands by: 1)sucking out water; and 2) building up soil until the land is too far above the water table to remain a wetland. Cattails and reeds can kill a river system. Aquatic weeds like water hyacinth, that die the first time a stream dries out, cannot kill a wetland, although they do great injury. Cattail sloughs really are a part of our dustbowl phenomenon.
There are several ways to convert suitable(not conatminated by arsenic and lead) cattail to biofuels.
Ethanol production was first demonstrated back in the 1970s. We’ve improved considerably since then, but even then, it was a winner and corn a loser. How much contamination does it take to make it unusable for ethanol? I don’t know. Cattail is also readily made into charcoal, the third world’s traditional fuel. The charcoal is powdery and needs briquetting. It can be directly briquetted and used for fuel. It can be digested into methane gas.
May 17th, 2009 at 2:50 pm
great post.
but the problem with cattail remediation is a lack of cattails in the great lakes. invasive plants called phragmites have taken over much of the shoreline in wetland areas, crowding out cattails and not providing much of anything in habitat or filtering.
jeff.
May 17th, 2009 at 5:22 pm
I don’t know from personal experience, but the online literature says that phragmites is useful in phytoremediation. It has been used successfully in briquetting and charcoal and gas generation of two types (anaerobic digestion and pyrolysis), and probably works for ethanol, too. I do not know of any group that has successfully used it for food, but otherwise they are nearly equivalent resources. Yeah, we do want to control it, but like cattails they are best controlled as a resource.
May 18th, 2009 at 6:41 pm
Finding such solutions that work in a symbiotic way is key to maintaining sustainable ecosystems. The worry is that using one element to counterbalance another will itself, at some point in the cycle cause its own imbalance. This sort of experimentation, backed by scientific results, may help us remedy the mess we’ve made of the planet.
May 20th, 2009 at 2:08 pm
What is hardly amusing is that these plants which are considered an invasive species dominating large areas of Florida and being controlled with chemicals at exorbitant cost to taxpayers are now being promulgated and used to treat wastewater from agriculture runoff (mainly sugar which is subsidized by the government). Remove the head of the snake and stop subsidizing large scale polluters with tax breaks and again subsidizing them by spending taxpayers money to clean up their mistakes.
June 18th, 2009 at 10:14 am
They tried this locally to me. A disused tin mine flooded and with tin comes arsenic. They trialled planting cattails in an artificial marshland rather than filtering or other treatment. They worked out they would need a ridiculous area of land to make any real difference and have just fill the whole area in.
On the whole (and not to repeat the points already made) an article which is well behind the times and lacking in any real understanding of the subject. Thumbs down.
July 29th, 2009 at 6:21 pm
When you process ethanol from cat tails you render the contaminates haremless.The more escue you put on them the larger they grow and the sugar content increases.There is no one solution for these problems but we are working on it..
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