Most ‘compostable’ bioplastics are anything but, says new report
Alden Wicker | Mongabay | July 31, 2024
Plastic trash has become one of the most visible global environmental crises of our time. Single-use plastics make up nearly half of all plastics produced, with 15 million metric tons of plastic now entering the ocean annually — equal to two garbage trucks dumping their loads into the sea every minute.
Plastics are everywhere: Found pole to pole, in clouds, drinking water, the stomachs of whales and seabirds, with bigger pieces degrading into centuries-lasting, often toxic micro- and nanoplastic particles that make their way into food and the human body — including our brains, breast milk and testicles.
With the next, and hopefully final, U.N. global plastics treaty negotiations set for a year-end meeting in Busan, South Korea, developing nations suffering the brunt of the crisis are calling for limits on plastic production. But industry groups propose a different solution that would allow single-use plastics production to continue apace: compostable and biodegradable bioplastics.
But as Mongabay recently reported, emerging research shows that bio-based plastics — made from corn, sugar beet, sugarcane, cellulose and other organics — can be just as toxic as petroleum-based plastics.
Now, a new report from Beyond Plastics, an NGO, makes a strong case that “biodegradable” and “compostable” plastics not only fail to live up to their sustainable promise — they could be harming ecosystems, farms that source bioplastic-contaminated compost, and people.
‘Worthless’ bioplastic compost
Many consumers will be surprised to learn that a certified plastic cup or container labeled as compostable can’t be put in backyard compost. It can often only be broken down under controlled conditions at a commercial composting facility, to which most communities lack access.
What’s more, according to the report, most U.S. commercial and municipal composters don’t accept compostable packaging, with only 46 of 173 U.S. industrial composters reporting they do. One reason is that organic farms, the main customers of composting facilities, aren’t allowed under current U.S. Department of Agriculture rules to use compost derived from compostable bioplastic packaging due to chemical contamination and bioplastic debris concerns.
According to voluntary American Society for Testing and Materials (ASTM) standards, a material is considered fully decomposed if more than 90% of it can pass through a 2-millimeter sieve. But that creates a loophole that allows compost to be chock-full of microplastics and nanoplastics. Research shows that fertilizers made at biogas facilities, for example, can have high levels of microplastics, including so-called biodegradable microplastics. A German study found that fertilizer coming from compost facilities contained large quantities of biodegradable plastics.
In an email to Mongabay, a representative of the Biodegradable Products Institute (BPI) said that, “Microplastics in compost are coming from conventional plastic contamination, not compostable products,” and pointed to a Spanish study showing no bioplastic contamination in commercially made compost.
However, other research shows that in complex natural environments, such as oceans or soils, bioplastics often don’t degrade as quickly as their proponents claim. One study found that biodegradable plastic bags were still fully intact three years after being buried.
“You’ll often have these promises made by companies that this is going to break down in five years, instead of 50 years, or 100 years, or whatever the comparison is with the traditional plastic,” says Susanne Brander, an associate professor and ecotoxicologist at Oregon State University. “But if you’re thinking about it from the perspective of an animal that might only live for a couple of years … it’s still going to be exposed to all of the breakdown products.”
According to Ulli Volk, deputy head of waste management and material flow management at Vienna Waste Management in Austria, who was quoted in the Beyond Plastics, bioplastics don’t add any nutrient value to compost and even harm the final product. “What composters really want are the food scraps; the bioplastic is collateral damage,” he said.
A February 2024 report by the Composting Consortium found that removing contaminants can comprise up to a fifth of a composting facilities’ operating costs. Biogas facilities, for example, remove all plastic wrapping, including bioplastics, from food waste and landfill it, thus negating the supposed benefit of using compostable foodware in the first place.
Meanwhile, consumers, misled by bioplastic labeled as compostable, will likely continue tossing it into the home compost bin.
