美国国家公共电台 NPR Replacing Plastic: Can Bacteria Help Us Break The Habit?（在线收听）

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If a civilization is remembered for what it leaves behind for later eras to see, our time might be known as the plastic age. A Silicon Valley startup is trying to get the plastic out of clothing and put something else in, something that will not last centuries. NPR's Christopher Joyce reports on their experiment in, of all places, a sewage treatment plant.

CHRISTOPHER JOYCE, BYLINE: Molly Morse runs a company in California that makes something called a biopolymers. They're like plastic but made in nature by living things. She calls her company Mango Materials, after her favorite fruit. She says she wanted to sound different.

MOLLY MORSE: We're, if you didn't notice, not your typical Silicon Valley startup company. Like, we're manufacturing polymers at the wastewater treatment plant. We're not a bunch of guys in a garage coding.

JOYCE: So how did this come to be? Well, when Molly Morse was in elementary school, she went to an aquarium and stumbled on an exhibit about plastic trash floating in the ocean.

MORSE: And there was this huge, gigantic, like, fish tank-type structure full of clamshells - like Styrofoam clamshells from McDonald's. And I was floored - like, completely horrified. Like, it changed my life. And I was like, that is freaking ridiculous, and I'm going to change it.

JOYCE: She followed through. Morse went to Stanford University and got a Ph.D. in environmental engineering. At a scientific conference in 2006, she met this young engineer, Anne Schauer-Gimenez.

ANNE SCHAUER-GIMENEZ: I mean, I think we were up till, like, 4 in the morning or something just talking about research and how this process works.

JOYCE: The process was how to make biopolymers. These are malleable materials similar to plastic, but they're made by living things, like cellulose from trees or silk from silkworms. And the bonus is biopolymers can be broken down into natural substances. The two engineers looked for ways to brew up batches of this stuff. They settled on bacteria, special kinds that make their own biopolymers, especially, says Morse, if you overfeed them.

MORSE: If we were to get really fat from eating a lot of ice cream or chocolate, we accumulate fat inside our bodies. These bacteria, same thing.

JOYCE: Schauer-Gimenez went for that.

SCHAUER-GIMENEZ: To me, microorganisms kind of run the show on planet Earth anyway. So why not let them help us with this process?

JOYCE: But the bacteria need lots of food to do that, and that's why they ended up at a sewage treatment plant in Redwood City, Calif. For the bacteria, sewage is food - or at least the methane gas from sewage. Treatment plants usually burn off the methane or just vent it into the air. Here, it's fed to bacteria.

ALLISON PIEJA: So this is where the magic happens in terms of the fermentation.

JOYCE: Engineer Allison Pieja is the third member of the Mango team. She's the bug expert and nurtures the bacteria in a fermenter, kind of like a big beer keg with pipes sticking in it like IV drips.

PIEJA: We add the methane and oxygen continuously and kind of drip in our secret sauce based on how the bacteria are growing.

JOYCE: The secret sauce is an additive that the team developed to keep the process going. Eventually, they bust open the bacteria and harvest the biopolymer. So far, they've shipped 1,700 pounds of that biopolymer to companies to test it in packaging and textiles. In a boardroom at the sewage plant, Morse shows me the results.

MORSE: So this was our fiber grade.

JOYCE: Brightly colored threads, plastic-y (ph) like polyester maybe. The hope is to weave the biopolymer into clothing to replace regular plastics - biodegradable clothing, which, says Schauer-Gimenez, freaks people out.

SCHAUER-GIMENEZ: Oh, my gosh. You're going to make a swimsuit out of your material. I'm going to go in the ocean, and it's going to biodegrade off of my body. And I'm like no, no, no, no, no. It doesn't quite work like that.

JOYCE: Biopolymers need warm temperatures and the right bacteria around to chew them up, and it takes weeks or months of constant exposure. Some kinds of biopolymers, ones made from plant materials like corn, take much longer to degrade, and that's given them a bad reputation.

RAMANI NARAYAN: Making a statement - biodegradable - that is misleading, especially to the general public.

JOYCE: Ramani Narayan is a chemical engineer at Michigan State University. He says the longer something takes to biodegrade, the longer it's litter.

NARAYAN: In that intervening period, it is going to have impacts. And that is what needs to be carefully considered.

JOYCE: Theoretically, biopolymers could be recycled. But Narayan points out that the recycling industry in the U.S. is already overwhelmed. Less than 10% of plastic currently gets recycled. Some research says even less.

NARAYAN: If we don't have the right waste management infrastructure in play, then all the things we do at the top end of it is going to be useless.

JOYCE: The Mango entrepreneurs say their biopolymer will break down faster than others and doesn't need to be recycled. Morse does acknowledge that there's a long way to go to get these biopolymers mainstreamed. In the meantime, she urges people to use less plastic and reuse things instead of throwing them away. But she's following her childhood dream to find something better than plastic.

Christopher Joyce, NPR News.