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Five years ago in Bodega Bay, just north of San Francisco, Joe Greene waded into the Pacific Ocean to collect a sample of the sea. He packed the containers of sand, silt, and surf in 38-liter coolers and drove back to his lab at the Chico campus of California State University.
The professor of sustainable manufacturing and mechanical engineering blended and pulverized two corn-based bioplastics—polylactic acid (PLA) and polyhydroxyalkanoate (PHA)—adding each to different samples of the Pacific he’d hauled back from the coast. Every day for the next six months Greene measured how much the bioplastics broke down. Throughout the study, commissioned by the California Department of Resources Recycling and Recovery, he found big differences in the biodegradability of the two bioplastics. In six months, only three percent of the PLA broke down. But for PHA, the results were much more impressive: a whopping 45 percent was degraded.
Greene and the State of California want to understand the environmental fate of PHA and PLA because it’s likely that at least one of these bioplastics could soon be flooding coastal waters.
Right now, many personal care products, including soap and toothpaste, are packed with tiny plastic particles called microbeads. A single 125-milliliter bottle of face wash, for example, could contain as many as 356,000 microbeads. And after use, they swirl down the drain, slip through the treatment plant, and flow into the water where fish may mistake them for food, inadvertently ingesting a toxic meal. Microbeads accumulate in organisms and release chemicals such as phthalates, bisphenol A (BPA), and those used as flame-retardants.
Currently, neither of the petroleum-based plastic microbeads on the market—made of either polyethylene or polypropylene—readily degrade in the environment. As such, they tend to accumulate. Concentrated by currents, microbeads contribute to the plastic pollution that plagues the oceans.
A number of companies that use the plastic spheres in their products, including Johnson & Johnson and L’Oréal, have vowed to phase them out. Meanwhile, legislators in California, New York, and other states have outlawed—or plan to—the manufacture and sale of microbeads. Now, it’s up to cosmetics companies to pick the best replacements.
Some companies already use or have turned to botanical alternatives, like apricot seeds and walnut shells, which are rougher than plastic microbeads and can exfoliate more effectively. Others, however, may opt for synthetic replacements that more closely mimic what they currently use, something like PLA or PHA. These bioplastics may stay in solution better than the botanicals and rarely react with users’ skin.
“When [companies] say they’re trying materials, they might be seeing how well that stuff hovers…in suspension,” says Marcus Eriksen, co-founder of the nonprofit 5 Gyres Institute, a group focused on eliminating marine plastic pollution. But those tests are geared at making a better cosmetic, not at assessing environmental aftereffects.
As scrubbing agents, PLA and PHA are both viable options. But their environmental fates are very different.
Both PLA and PHA biodegrade over time, but they do so under different conditions. PLA readily breaks down in industrial compost piles, but in the ocean the temperature never gets high enough to cause it to decompose. But as Greene saw in his lab, bacteria in the saltwater eat the PHA. The saltwater helps move the microorganisms to the PHA and they gobble it up. When the corn-based PHA courses into the ocean, “you’re feeding the bacteria,” says Greene. “And they’re pretty hungry.”
Even after he finished his study, Greene continued monitoring how quickly the plastics degraded. He found that while 45 percent of the PHA degraded in six months, 60 percent was gone by the end of the year. “PHA can fully biodegrade, but it might take two years,” he says.
Yet, so far, companies seem to prefer PLA to PHA—perhaps because it’s clear (unlike the opaque PHA), cheaper, and the manufacturing process is easier to scale, says Greene. Some manufacturers are pushing for legislation that would allow them to use PLA in their products, says Eriksen, even though that wouldn’t solve the ocean pollution issue.
Companies have so far remained tight-lipped about which alternative they’ll choose. Johnson & Johnson, for example, says its research is proprietary. Soon enough, though, consumers will be able to read their decision on the package. This year, Johnson & Johnson and Unilever will stop using petroleum-based microbeads. Many others plan to follow suit within the next two years, according to Beat the Bead, a campaign against microbeads in cosmetics.
Cosmetics companies have options in front of them, says Greene, but if they want a microbead replacement that will remove the threat of creating more plastic pollution, they should go with PHA. “It’s there; it’s ready for them.”