The Great Pacific Garbage Patch, a vortex of trash in the North Pacific, spans hundreds of miles. The waste, much of it plastic, is suspended like confetti under the waves and on the surface. “It’s so dilute, it’s probably impossible to clean up,” says Henry Carson, a professor of Marine Science at the University of Hawaii. “Our best bet is to start by not putting any more plastic in.”
Keeping litter out of the ocean isn’t easy, though, and most biodegradable plastics don’t break down well in marine environments—they require the relative warmth of soil or a compost heap. A new plastic on the market degrades quickly both on land and in seawater. Polyhydroxyalkanoate plastic, better known as PHA, has been around in labs for decades but became commercially available only in October 2010 through a joint venture between Cambridge (Mass.) startup Metabolix and Archer Daniels Midland. In the past year, 57 companies, including PaperMate and Cortec, started using the Mirel-brand plastic to manufacture products like pens, packaging, and fishing nets. “It’s like a miracle material,” says Jo Ann Ratto, a polymer research engineer with the U.S. Army who has studied the plastic.
PHA is produced by bacteria, which use it to store energy in the same way that humans store energy as fat. It will degrade in any microbe-rich environment because bacteria recognize the material as food and gobble it up. “If a bag made from PHA plastic is put into a natural lake, the ocean, a home compost facility, the woods, or any place where there are natural microbes present, they will consume it and it will disappear,” says Richard P. Eno, chief executive officer of Metabolix.
Ratto’s group at the Army’s Natick Soldier Research, Development and Engineering Center recently ran a study on how well biodegradable materials decompose in ocean waters. After 26 weeks submerged in seawater with sediment, samples of cellophane and polylactic acid, two commonly used biodegradables, lost less than 20 percent and less than 1 percent of their mass, respectively. The PHA samples completely disappeared in less than five weeks. “It’s very rare to get something that degrades in a marine environment, never mind rapidly like PHA,” says Ratto.
Metabolix was spun out of the Massachusetts Institute of Technology in 1992 and has spent the decades since then perfecting its production process. The biggest challenge was genetically modifying microbes to produce large volumes of the plastic. They also had to figure out how to produce different grades of PHA plastics appropriate for products as diverse as shopping bags and hard hats. “It took us a while, but we accomplished it,” says Oliver Peoples, the company’s co-founder and chief scientific officer.
PHAs are more versatile than most competing biodegradables because they maintain their structure at up to 300F. Some alternatives can’t even be used “to make a spoon or a fork because you can’t put them in a hot coffee—they would just melt,” says Ratto. She adds that the Army has found all commercial grades of Mirel to be nontoxic. Zoë b Organic, a manufacturer of sustainable children’s products, is making Mirel beach toys that will go on sale this spring at Pottery Barn Kids. “Like with any material, there’s a learning curve to using it,” says the company’s founder Valerie Lecoeur. “But then it’s perfect, very sturdy.”
The major hurdle is price. PHA costs $2.25 to $2.75 a pound, while petroleum-based plastic costs as little as 60¢ a pound. “We see substantial demand for the product at current pricing levels,” says Eno. Metabolix also wants to move away from corn, which it currently uses as a feed source for its microbes. Peoples says the company is looking into greener alternatives like switchgrass. “The more Mirel gets out there, the more innovation that happens, the better it will get,” says Peoples. “The most challenging thing you can do is introduce a new material.”
Metabolix’s plant has the capacity to produce 110 million pounds of plastic annually—about 0.02 percent of global production. The company hasn’t released revenue numbers for 2011 but Eno says that international interest in the product is high and the company is helping 100 new customers develop products. Still, he’s under no illusion that Mirel means the end of the Great Pacific Garbage Patch. “The ocean is the single biggest landfill for plastic in the world,” says Eno. “The problem is just so big.”
The bottom line: Metabolix’s biodegradable plastic completely breaks down in seawater but is up to four times more expensive than traditional plastic.
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