Making Plastics out of Switchgrass Plants
Metabolix Inc. Creates a 100% Biodegradable Plastic
Jan 22, 2009
On the roof of a Cambridge, Massachusetts company, a green house hides a variety of switchgrass, Panicum virgatum, which produces plastic in its leaf tissues. The plastic begins with Nature and since it breaks down, it can end in Nature as well.
A New Approach to Bioplastics
Bioengineers have already made plastics out of feedstock, in particular corn sugar. But the new idea is to avoid dipping into the plants' food resources.
Brian Igoe, vice president of Metabolix Inc. walks among the plants and explains that switchgrass grows indigenously throughout North America from Mexico up to Canada. "It's commonly known as prairie grass. What's inside these leaves is different than in prairie grass though!"
The plants naturally synthesize a low quantity of polymers, the chains of molecules that make plastic. They use those molecules to develop and make more plant cells. So researchers at Metabolix Inc. came up with a technique of genetic engineering to have the plant grow more of those building blocks of plastic. By adding these new genes, they allowed the plant to divert some of its cells into the building blocks of plastic.
A Biogenetic Recoding
To create the transgenic switch grass they first had to gather the plant's genetic information. "We had to make what's called a genetic construct that has all the genetic information necessary to basically reprogram switchgrass to make the bioplastic," says Dr. Kristi Snell, Plant Metabolix Inc. Engineer. Once they knew which gene was coding for the polymers' synthesis, they only had to enhance and boost the process.
"And what happens is that when the polymer chains form, you can see through a microscope these granules that look like balls inside the plant cells," adds Dr Oliver Peoples, chief scientific officer Metabolix Inc..
Once the cells were filled up with those polymers, the team had to extract them from the switch grass, and then fold them into resin pearls. Heating up those resin pearls they can fabricate any object they want: cosmetic packaging, plastic cups, razors, cell phones... and the list goes on.
Totally Biodegradable Plastics
"Although the process is different, the end product is the same. Basically just plastic," says Peoples. However these are not just regular plastics made of petroleum and which take hundreds of years to break down. Metabolix plastics are made from natural material, which are completely biodegradable in a wide range of environments like soil and marine environments. Biodegradation can be fairly rapid, from weeks to months.
But, it will take some time before bioplastics replace conventional plastics. Metabolix Inc.'s switch grass innovation hasn't yet made it to the industrial level, but Igoe confesses that confidentiality agreements were signed and that we should see bioplastics out of switchgrass prairies popping up in a couple of years.
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