University College Dublin (UCD)
Des bactéries qui mangent des vieux plastiques (PS, PET …) pour en faire … des plastiques biodégradables ! Une nouvelle forme de recyclage ? Voici plusieurs artciles sur le sujet.
Copenhagen—The employee of the decade in green tech is scum.
University College Dublin (UCD) has come up with a way to recycle old plastic bottles and containers with microorganisms. The end result—the thing that comes out of the bacteria’s digestive system–is a new piece of plastic.
The difference, however, is that the plastic that comes out of the process is biodegradable. It can go safely into a landfill and will disappear over time, said Kevin O’Connor, the lead researcher on the project during a presentation at Copenmind, a university tech transfer conference taking place this week.
If the process can be brought up to an industrial level, it could help the world get rid of the nation-sized mass of plastic that humanity has generated. Right now, there are two general ways of dealing with old plastic.
Some countries, like England and Ireland, ship it to other countries after doing the green thing and recycling. Plastic bottles have a low recycling value; hence, a lot of the plastic ends up in landfills forever. (But the Irish are big into recycling—a 15 cent tax on plastic bags dropped their use by over 99 percent, O’Connor said.)
The other method to “recycle” plastic is to burn it. Sweden, Switzerland, Germany and other countries practice it. It yields useable energy, but it’s not the cleanest practice in the world either.
UCD’s process works like this. Polypropylene (plastic) is cooked until it turns into a styrene oil. The oil is then fed to microorganisms, which metabolically turn it into globules of fatty acids.
When 60 percent of the bacteria consists of those fatty acids, the microorganism is split open and the harvested fatty acids are converted to a biodegradable plastic. See why bacteria make such good workers? Try to do that to your new hire from Cal State Fullerton and the first thing he’ll do is file a worker’s compensation claim.
It’s good plastic too. The glass transition temperature—the temperature that makes it brittle—is a low minus 43.3 degrees Celsius, so it’s freezer safe. You can heat it to 278 Celsius.
“But it will degrade in a compost heat at 32 degrees because the microorganisms (in the landfill) release enzymes,” he said.
Industrial microbiology is the basis of a number of other start-ups, including Cambrios (microbes making industrial chemicals) and AgraQuest (biopesticides).
Melting the plastic into an oil requires energy. The overall balance, however, is better than if you made a second, separate bottle, O’Connor asserted. A kilogram of plastic yields 350 grams of new plastic. The missing oil goes to the microorganism: they feed off the oil to grow.
The group has filed for a few patents. Next year, it wants to move out of the lab and do a multi-kilogram recycling center with a large waste company.
Keep your eye on Ireland in cleantech and advance science, by the way. For years, the Irish tech industry primarily concentrated on serving as an outsourcing destination for multinationals. But in about 2000, the government—realizing that Ireland was no longer a low-cost center—began to invest in technology transfer center and incubators.
The pitch made to scientists is straightforward. Unless researchers can’t come up with interesting commercial applications, funding may get cut during austerity times, Pat Frain, who runs NovaUCD (the school’s incubator) told me earlier this year. Plus, you might become incredibly wealthy. Other incubation centers in Ireland are working on ocean power, semiconductors and material science. (See this masterpiece of cinema for more.) Another interesting project at UCD: BiancaMed, which has a wireless device that can tell you what happens to your body while you sleep.
Whether or not the incubator program ends up creating successful start-ups, however, won’t like be known for another five years.
http://greenlight.greentechmedia.com/2008/09/02/a-new-bioplastic-made-by-bacteria-518/
http://www.irishtimes.com/newspaper/innovation/2008/0901/1219875255380.html
04-Aug-2008 –
A research group based at University College Dublin claims it can convert plastics such as polystyrene (PS), polyethylene terephthalate (PET) and mixed plastics into a biodegradable polymer.
“We are unique in this ability to convert petrochemical plastics to biodegradable plastics,” he claims.
“We are collaborating with other scientists who will start to process our polymer with a view to developing products for packaging and other applications,” added O’Connor.
A two-step approach that converts a common plastic into a biodegradable polymer could cut the number of packing peanuts and Styrofoam cups that end up in landfills, researchers suggest.
In 2003, U.S. manufacturers produced more than 2 million tons of polystyrene to make such items as food packaging, packing materials, and furniture. Nearly all of this plastic was discarded, according to the Environmental. Protection Agency. There is little demand for recycled polystyrene because it’s of lower quality than the polystyrene made directly from petroleum components, notes Kevin E. O’Connor of the University College Dublin.
Last year, O’Connor’s group reported that the bacterium Pseudomonas putida CA-3 could metabolize pure styrene, the precursor of polystyrene, and convert it into polyhydroxyalkanoate (PHA), a biodegradable polymer that can be made into good-quality plastic. While other members of this microbe family turn sugars and other plant-based materials into PHA, converting styrene is rare, says O’Connor.
In an upcoming Environmental Science & Technology, O’Connor and his colleagues describe adding a chemical step to the microbial process, thereby changing polystyrene into PHA.
First, they heated the polystyrene to 520[degrees]C in a closed reactor, which broke down the polymer chains and produced styrene oil containing a few other chemical compounds.
The researchers then cooled the liquid and added it to P. putida CA-3 growing in the lab. O’Connor says that he was not sure whether the microbes would tolerate the impure styrene, but “they grew well. You can take your dirty oil and just feed it to the bacteria rather than having to clean it up.”
As in their previous work, the researchers induced the bacteria to turn styrene into PHA by limiting the microbes’ supply of nitrogen, which they need to make amino acids. Under such conditions, which don’t support growth, some bacteria go dormant, says O’Connor, but others react by storing carbon as a polymer that will be useful if more-favorable conditions return.
After 48 hours of fermentation, the bacteria had produced 1.6 grams of medium-chain-length PHA from 16 g of styrene oil, the researchers report. This biodegradable polymer, with repeating units of 6 to 14 carbons, could be used to make paints or medical devices.
“We recognize that it’s a nice concept, but it needs to be improved to make it more economical,” O’Connor says. The researchers are now investigating ways to improve the 10 percent styrene-to-PHA conversion rate.
Stephen McCarthy of the University of Massachusetts at Lowell agrees that the approach is not practical at this stage but adds that it “could be of value in the future.”
However, he notes that rather than making biodegradable materials from petrochemical plastics, it would be better to use only biodegradable plastics in the first place. They can be made from renewable resources such as farm crops. “That’s going to help us to wean ourselves off of fossil fuels more than this particular approach,” says McCarthy.
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http://findarticles.com/p/articles/mi_m1200/is_/ai_n16108538
K. O’Connor lab home page http://www.ucd.ie/biocatal/
Publications http://www.ucd.ie/biocatal/Publications.htm
