Plastic Page 25
The locked greenhouse down the hall, however, contained Peoples's ultimate dream. In that small rooftop space, a miniature prairie sprouted under banks of fluorescent lights. There were dozens of pots filled with switchgrass plants that had been genetically modified to grow PHA in their cells. "If you look at the stems and leaves of this switchgrass here, it has this kind of white finish to it," Igoe said, holding out a leaf for me to examine. That slightly white cast was the PHA; it made up about 6 percent of the plant's tissue. Nearby were several pots of tobacco plants, which were also growing PHA. (Tobacco DNA is so easily manipulated, the plant is the botanical equivalent of the lab rat in gene technology.) One day, the company hopes, plants such as these could be a source of useful plastic. The plant would be harvested and dried, the PHA extracted and turned into Mirel, while the leftover biomass could be burned for energy.
Peoples wasn't the first to see the possibilities of those micro plastics producers. Scientists at Imperial Chemical Industries in Britain tried to commercialize the technology in the 1980s with no success and passed the torch to Monsanto. In the late 1990s Monsanto reported that it had succeeded in creating a PHA plastic, and one credit card maker announced it would issue a "green earth" credit card from the new polymer. But before that could happen, Monsanto decided to pull the plug on its entire bioplastics division. Plant-based plastics were considerably more expensive than those made from fossil fuels, and Monsanto wasn't convinced there was a market willing to pay the added costs of going green.
But Peoples is certain the math can be made to work and that there is a market eagerly awaiting the arrival of green plastics. Grain giant Archer Daniels Midland has bought into Peoples's vision. In 2004, ADM formed a joint venture with Metabolix to start producing Mirel on a commercial scale. After repeated delays, the joint venture's plant in Clinton, Iowa, finally fired up in early 2010.
Bioplastics do cost more than petro-plastics—PLA is two to three times the price, though Davies said that price difference begins to evaporate when the price of oil passes eighty dollars a barrel. Mirel is even more expensive, but Peoples insists he isn't trying to compete with conventional plastics or, for that matter, PLA. He's positioning Mirel as "a premium product," a polymer that can be made into a film or foam or a rigid material and that has one big advantage over petro-based plastics: it readily biodegrades. That's the virtue Peoples is depending on to conquer just a handful of carefully picked end markets, including packaging, agricultural applications, and consumer products, such as gift cards. Indeed, in 2008 Metabolix struck a deal with Target to provide enough Mirel for millions of gift cards for the Christmas season that year. The cards gave Target an opportunity to shore up its green credentials while providing Metabolix a visible platform to announce its new plastic to the world.
Mirel and Ingeo are still a long way from being household names. When production at its Nebraska plant reaches full capacity, NatureWorks will still be making only 350 million pounds of its bioplastic a year; Metabolix is able to produce about a third that much. Even if you count the various other biopolymers in existence and under development, the total barely registers in a world awash in fossil-fuel-based plastics.
Still, bioplastics are generating so much buzz because they're seen as holding the answer to many of our plastic woes—the rehabilitated partner who can transform this troubled relationship we're in. But before we commit to yet another family of polymers, it's worth asking the question Tim Greiner posed: Just what problems do bioplastics solve?
When I asked Michigan State polymer chemist Ramani Narayan, he had a single answer: the looming threat of climate change. Because biopolymers are made from "renewable sources of carbon"—what the rest of us call plants—they can reduce the amount of global-warming carbon dioxide we're sending up into the atmosphere. The CO2 that's released at the bioplastic's end of life can be recaptured by the new plants that sprout in the next season. Bioplastics move us back inside the protective loop of the natural carbon cycle: the neatly balanced output and uptake of CO2 that has sustained life on earth for eons. Even a single-use gift card that's immediately tossed in a landfill stays within that natural cycle if the card is made of a biopolymer, said Narayan. Petro-plastics, on the other hand, exist outside that loop, which is why their CO2 emissions constitute a climate threat.
The benefit Narayan describes is quantified in the complex accounting of carbon calculations. Fossil-fuel-based plastics generate anywhere from two to nine kilograms of carbon dioxide for every kilogram of polymer produced. Plant-based plastics generate far less CO2, even when you factor in all the oil used to fertilize, grow, and harvest the crops. PLA produces just 1.3 kilograms of carbon dioxide for every kilo of polymer produced. Mirel's carbon profile is a little higher because it takes more energy to make, but Narayan says it still beats conventional plastics.
Narayan has spent decades developing corn plastics. But he's not wedded to corn as a feedstock—any type of plant-based raw ingredient would have the same beneficial effect, he said. Indeed, agricultural crops—especially genetically modified crops—are probably not the best source of feedstocks. Critics point out the perversity of growing a food crop to make plastic in a world full of people who are hungry, and there's the additional drawback of the large amounts of land and water and oil-based fertilizers needed to raise it. A more sustainable and economical source of raw materials is waste—the vast quantities produced by us and the rest of the natural world. After all, conventional plastics are derived from the waste produced in processing fossil fuels; the ingenious use of that waste was what gave plastics an economic leg up in the first place.
Bioplastics producers are already exploring the possibilities posed by downed forest trees and the leftovers from paper and pulp production—surprisingly large sources of cellulose—as well as yard clippings and the remnants of harvested crops, such as corn stover and sugar-cane bagasse. By one estimate, such sources add up to 350 million metric tons a year, enough to substantially supplement fossil-fuel feedstocks. But there's also the waste we produce every day—our garbage, and even our sewage. Scientists around the world are dumpster-diving for waste materials that can be used as plastic feedstocks, exploring the possibilities of chicken feathers, orange peels, potato peels, carbon dioxide; even the methane emitted from landfills that is now sometimes recovered for energy. Stanford University chemist Craig Criddle is working with methane-eating microbes, relatives of the ones employed by Metabolix. He's found that after gorging on methane, they can produce prodigious quantities of a polymer similar to PHA and that the polymer can biodegrade back to methane. Though the technology is still in early stages, it promises a neatly closed production loop. So too does the work of Cornell University chemist Geoff Coates, who has developed a way to capture carbon dioxide emitted from the scrubbers on power plants and transform it into a biodegradable type of polypropylene carbonate plastic; it's now being commercially produced in small batches. None of these alone could replace the fossil fuels used in plastics, but there is no reason to believe we need just a single replacement. Part of petroleum's magic is that it has been able to do so many things so well. A more sustainable approach to plastics production (not to mention energy production) will almost certainly require developing multiple resources in the context of what is locally available and feasible. One measure of success will be how well bioplastic products, such as biopolymer credit cards, reduce an individual's carbon footprint.
But that's not the only plastic problem that biopolymers address. They also promise a safer chemical profile—certainly safer than the PVC typically used in credit cards. No hazardous compounds are required to knit a PLA or Mirel daisy chain. As Rossi noted, "I'd much rather live next to NatureWorks' plant in Nebraska than a petroleum-refining facility." And as producers of green plastics, NatureWorks and Metabolix have a vested interest in protecting how their resins are used and processed by manufacturers farther down the supply chain. "This sounds self-serving, but we are being held to a higher st
andard," said Davies. "From the get-go, we have to follow this extended producer responsibility model where we can't put products into the market without knowing where they go and what's happening to them."
Both NatureWorks and Metabolix claim to be committed to avoiding the addition of harmful chemicals by downstream processors and to being practitioners of the evolving science known as green chemistry. (Green chemistry goals include making synthetic chemicals with as few toxic substances and processes as possible, generating the minimum amount of waste, and producing compounds that won't persist in the environment. ) NatureWorks, for instance, requires any manufacturer using its plastic to abide by a "prohibited substances list," which bars the use of various known persistent organic pollutants, endocrine disrupters, heavy metals, carcinogens, and other dangerous chemicals.
If you browse the shelves of bioplastic products, you'll notice that the most common problem they claim to address is plastic's stubborn durability. "Go ahead, throw it away! No composting required," boasts a maker of picnic forks, suggesting that once discarded, they will simply melt away. Fork gone; problem solved. But advertising, even the greenest, seldom tells the whole story.
I thought I knew what biodegradable meant, but in talking with experts, I came to realize it's a far more complicated process than my hazy notion of something just "breaking down." The term has a precise scientific meaning: biodegradable in this context means that the polymer molecules can be completely consumed by microorganisms that turn them back to carbon dioxide, methane, water, and other natural compounds. "The key word is complete," cautioned Narayan. It doesn't count as biodegradation if only a portion of the polymer can be digested.
That distinction is why Narayan has criticized my purportedly biodegradable Discover card. His studies show that despite the PVC-microbe bait, the micro-critters consume only about 13 percent of the card; after that, the process plateaus. It's also at the heart of a controversy over a rash of plastic bags that are marketed as "oxo-biodegradable." They're made of conventional plastics blended with an additive that causes them to break up when exposed to the sun. The bags do quickly crumble, but there's little evidence that the resulting plastic bits are ever fully consumed by microbes. Instead, critics contend, they may simply litter the earth with yet more tiny flakes of plastic.
Another complication affecting a product's biodegradability is that the process unfolds in different ways, depending on the material, the setting, and the microbes in residence. A felled tree is eminently biodegradable. In a steamy rainforest teeming with fungi and microbes, it could be gobbled up in a matter of months. Yet if it topples in the hot, dry desert where there are few microorganisms around, it will petrify long before it can be consumed. And if it sinks to the anaerobic bottom of a river, it will be preserved for centuries because the microbes that digest wood need oxygen to do their work. Plastics are intrinsically more difficult to break down than wood, but their capacity to biodegrade is a function of a polymer's chemical structure, not its starting ingredients. There are fossil-fuel-based plastics that will biodegrade (often used to make compostable bags and film), and there are plant-based plastics that won't.
In principle, both PLA and Mirel are biodegradable. In practice, it occurs more easily with Mirel. I could take a used Mirel gift card and toss it into my backyard compost bin, where microbes would digest it, creating lovely rich dark humus, over the course of a few months. The same would happen, though at a slower rate, if I lost it in the park, or even if I dropped it in the ocean. Mirel is just about the only plastic available today—petro- or plant-based—that will break down in a marine environment. So while you wouldn't want to build a dock with it, it could be a great material for plastic packaging, especially of foods and goods designed for shipboard use. Indeed, the U.S. Navy is exploring the use of Mirel utensils, plates, and cups.
PLA is trickier. It will biodegrade, but only under optimal composting conditions, which are challenging to achieve on one's own. Given the so-so state of my backyard compost bin, I suspect that if I deposited the PLA iTunes gift card there, it would remain intact for a good long while. Really mobilizing the microbes that can pry apart PLA's long polymer chains requires a balance of oxygen, moisture, aeration, and steady temperatures between 120 and 140 degrees—in short, the sort of conditions most readily found in an industrial composting facility. Unfortunately, there are only about two hundred to three hundred facilities in the country that process consumer food waste, and far fewer communities that actually collect residential food scraps for composting. Most of those are located in California and Washington.
As with any new technology, it takes time for a supporting infrastructure to develop. NatureWorks hopes that PLA products can eventually be chemically recycled, through a chemical process that breaks them back down to the starting ingredient, lactic acid. But as of 2010, there's only one facility in the world capable of doing that. At the moment, the plastic is creating a mini-crisis in the recycling world, where all is geared to conventional plastics. PLA is increasingly used for food packaging, but many consumers don't realize a PLA bottle can't go into the recycling bin. "We're freaking out about these," said one executive at San Francisco's Recology as he showed me a plastic water bottle made of PLA. The bottle looked exactly like one made of PET, yet it could contaminate a batch of PET being recycled. While some cup makers have started using green or brown logos and labels to indicate the cups are made of PLA, as of yet there's no standard system for differentiating biopolymers.
The allure of biodegradability is understandable. (Though it's ironic to see it assume the kind of marketing cachet for plastics that durability once held. I can't imagine any plastics maker today using this ad that ran in the 1980s: "Plastic is forever ... and a lot cheaper than diamonds.") Still, the ability to biodegrade is neither a panacea for pollution nor the end-of-life solution to all things plastic.
Consider all the products, like that Discover card, that claim to break down in a landfill. It's a myth and a misplaced hope, said Steve Mojo; he's the director of the Biodegradable Products Institute, a trade group that polices the biopolymers world, certifying products that pass international standards of compostability and biodegradability. Ideally, nothing should biodegrade in a landfill, he explained. Landfills are engineered to deter that process as much as possible because it generates greenhouse gases. Yucky as it may be to think that our garbage will outlast us as well as our great-great-grandchildren, that's actually preferable to having it break down and give off methane, the most potent climate-change gas. Listening to Mojo describe how landfills work, I thought about the many biodegradable bags that are sold for collecting dog poop and that most people simply throw into the trash. These well-intentioned folks may be hoping that by their using biodegradable bags rather than regular plastic sacks, their pooches' poop will be more likely to decompose. But as with anything deposited in a landfill, "it's going to be preserved," said Mojo. "So when [future] generations go out and excavate the landfill, they will know we had a lot of dogs."
Where biodegradability makes sense is in products that are associated with food or organic waste (the sort that, unlike dog poop, can be safely composted), such as disposable plates and cups and cutlery, snack packages, and fast-food containers. All are single-use items that aren't often recycled today, especially the ones made of film. (Biodegradability would also be useful for the millions of pounds of agricultural film used by farmers every growing season to block weeds from sprouting among crops and that no one has found a way to economically recycle.) Making these kinds of products out of biodegradable bioplastics not only provides a solution for disposing of the package, it helps encourage the composting of food waste—which is a far bigger part of the garbage stream than plastics. Americans throw away more than thirty million tons of food waste each year, and most winds up in landfills. Zero-waste advocates see compostable plastic packaging as a two-for-one solution.
But is biodegradability the answer to the waste problems posed by quas
i-cash plastic cards? Maybe. But what about redesigning them so that it's easier to load on new credit, allowing a card to be reused? That way, fewer new cards would have to be made. As for credit cards, why not reduce the frequency with which new cards are issued for existing accounts? Or expand on the few paltry card-to-card recycling programs that currently exist? Or make the cards out of a less toxic plastic than PVC so they can be more easily recycled? That's the route some European banks have gone and the one chosen by HSBC when it wanted to issue a more earth-friendly credit card for its Hong Kong market. Its green card, unveiled in 2008, is made from the most recycled plastic, PET. And it's backed by even more tangible ecobenefits: digital billing, which cuts down on paper waste, and the bank's pledge that a portion of all spending will be donated to local environmental projects.
Manufacturers have long chosen the plastics for their products on the basis of price and functionality. But creating a more sustainable relationship with plastics will require a new dexterity on our part. It will require us to think about the entire life cycle of the products we create and use. A green plastic that's suitable for one application may not be suitable for another when all environmental factors are taken into account. Biodegradation may not always be the best answer.
Consider the recent report in the New York Times that some designers of furniture and other housewares are taking pains to make sure their products are biodegradable. At one level, that's a laudable application of cradle-to-cradle thinking. Montauk Sofa, for instance, designed a line of couches in which all the components were made of organic, nontoxic materials that could biodegrade. As the chief executive of the company told the Times, "At first the whole idea was to have as little impact on the environment as possible. And then I started to think, wouldn't it be great to have no impact? Then it was, hey, what if the sofa just disappears when you're done with it?"