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The Dirty Truth About Compostable Plastic

Nov 04, 2023

Sure, these products could be better than regular old plastic. Right now, they’re not.

In 2023, the options for a build-your-own fast-casual lunch can include wild Alaskan salmon, harissa honey chicken, cauliflower shawarma, seasonal roasted zucchini, preserved lemon vinaigrette, za’atar bread crumbs, creamy vegan feta, and skhug. But whatever you choose, it will all inevitably be served in a compostable bowl. As an office worker blessed (and cursed) with endless overpriced meal options, I have shoveled way too much random food into my mouth from a compostable vessel, using a compostable utensil.

The forks, in particular, are not prone to subtlety: Some are embossed with the word COMPOSTABLE; others are green, in case anyone forgets they are “green.” But the compostable-packaging takeover has been tough to miss. Perhaps you have gotten leftovers in a compostable container, stuffed groceries into a compostable produce bag, or sipped coffee out of a compostable straw. Compostable packaging “is growing, and growing a lot,” David Henkes, a food-industry analyst at Technomic, told me. By 2021, 7 percent of all food-service packaging was compostable, Henkes said; its share has almost certainly grown since then, especially in major cities. Among the companies that now use it: Trader Joe’s, Whole Foods, Cava, Sweetgreen, Panera Bread, Taco Bell, and Frito-Lay.

But although compostable packaging is easy to spot, compost bins to put it in are not. All of my office forks and soggy fiber packaging have gone straight into the kitchen trash, just like normal plastic would. Only a tiny fraction of this compostable packaging and plastic, it turns out, is actually getting composted. Even if restaurants, homes, and office buildings have composting bins, in most places this pile of compostable trash has nowhere to go: America doesn’t have the composting infrastructure to deal with it. These products might have the potential to be better for the planet than traditional plastic, but right now, compostable plastic is just plastic.

What makes plastic so great is also what makes it so terrible. The substance, created from fossil fuels, is cheap, moldable, and so durable that most plastic that humans have ever produced still exists. Compostable plastic is made by chemically manipulating plant sugars such as corn starch and sugar cane to achieve similar properties; the flimsier, cardboardlike compostable bowls are molded out of bamboo and other plant fibers. The promise of these products is the same: Whereas a plastic fork or bowl might get used for just a few minutes before lingering in the environment forever, a compostable version degrades over time, not unlike an apple core you throw away in the woods. Only more slowly. Much more slowly.

In most cases, compostable plastic is compostable only under very specific conditions. “It’s not like what you would do in your yard if you tried to compost a banana peel,” Sarah-Jeanne Royer, an oceanographer at Hawaii Pacific University, told me. “You need to have access to a composting facility.” And a home compost pile is like the industrial version in the same way that a pickup-basketball game among preteens is the same sport as the NBA. Fruit and vegetables start to dissolve into soil within a few weeks; meat takes a little longer. Eventually, any form of compostable plastic should break down too, Frederick Michel Jr., a compost expert at Ohio State University, told me. Eventually. In one study, compostable plastic bags buried in soil for three years were so sturdy they could still hold a full load of groceries. Royer submerged a type of compostable plastic in seawater and could not find any signs of degradation 428 days later.

A commercial plant speeds that timeline up to just a few months, using machinery that encourages the best possible conditions for composting. The bugs and microbes that break down organic matter release heat in the process, and all the rotting waste at a composting facility can routinely hit temperatures of 160 degrees. You will never achieve that at home.

But good luck finding one of those facilities. America is churning out all of this biodegradable packaging without the ability to process it: The entire country has roughly 200 full-scale food-waste composting plants, and about three-fifths of those accept compostable packaging, according to not-yet-published research from BioCycle. In practice, getting your compostable plastic into one of those plants means living in one of just a few cities—San Francisco, Seattle, parts of New York—that picks up compost just like trash and recycling and trucks it to a plant. Everyone else is left in compost deserts, Michel said. In Ohio, “the only way for me to compost is in my backyard,” he said. Cities as big as Atlanta do not have a composting plant within an hour’s drive; the entire state of Alabama does not have a single place that can digest compostable plastic.

The companies using these products are aware of these limitations. Consider the 10-email exchange I had with Cava, trying to confirm that the fast-casual chain does in fact use compostable bowls, which the spokesperson originally outright denied. It ended with the spokesperson acknowledging that “CAVA’s bowl containers are primarily made of bagasse” (which is made from sugar cane and is compostable) but that “there are some limitations to the availability of composting facilities, which is why CAVA is careful about how they talk about it.” And in the long term, companies who are handing out single-use items should be trying to switch over. A single fork turned back into biomass is more biodegradation than most of the plastic in human history has ever done. So much of the world’s plastic is used for packaging that, with the proper infrastructure, “if everything that’s now plastic was made out of compostable plastic, then it would dramatically change what we are looking at,” Ramani Narayan, a chemical engineer at Michigan State who studies renewable plastics, told me. The equivalent of a dump truck’s worth of plastic sloshes into the ocean every minute, entangling wildlife, poisoning the soil and water, and splitting into microplastics that accumulate up the food chain; replacing that with something even marginally less permanent would be a positive change.

As long as compostable plastic is ending up in landfills, though, the math is less favorable. In a dump, these products may not biodegrade for more than a century. And they can have an additional knock against them: In the anaerobic conditions of a landfill, certain types of compostable plastic can also spew methane, a greenhouse gas that is 25 times more potent than carbon dioxide.

Compostable plastic might backfire in other ways too. A push against single-use plastic has made lots of people reconsider, even if briefly, whether to use that plastic plate or bowl or straw; compostable products implicitly signal to consumers that they can use these instead and walk away with a lighter conscience. “Marketing people are always asking me, ‘So what about compostable plastic?’” says Claire Sand, a packaging consultant for major companies, because consumers badly want this to be the answer to single-use plastic. In the U.S., all certified compostable products are required to have a label making clear that they are meant to be composted in “aerobic municipal and industrial composting facilities.” But fine print is easy to overlook with all the green colors and brand names, including EarthChoice, Eco-Baggeez, Greenware, and Responsible Products. And though a plastic takeout container can live a second life as pseudo-Tupperware, and a plastic bag as a garbage liner, many compostable versions just don’t cut it.

Both compostable plastic—and America’s composting network—will get better. Diverting compostable stuff from landfills is so important for making a dent in emissions that the federal government is throwing $90 million at it. Plenty of companies are also trying to make better compostable products: Can I interest you in plastic that turns into protein powder, banana-peel plastic, avocado plastic, and seaweed plastic? Still, finding the right balance between durability and compostability is tough. No one wants a box of spoons that rots after three weeks in your cupboard.

If you must buy compostable plastic products, some are better than others. Look for items that are certified by the Biodegradable Products Institute (BPI), and whenever possible, TÜV OK Compost Home, Michel said, a European standard that signifies that the plastic should disintegrate even in home compost piles. And try to avoid anything made of polylactic acid, or PLA, which is the among most onerous biodegradable plastic to compost, though also the most popular. Broadly speaking, the less something is like real plastic, the easier it is to break down. The best compostable utensil is not embossed with COMPOSTABLE or green in color but made of untreated wood. “It is inherently compostable and does not really pose any more of an issue than a branch falling off of a tree,” Michel said.

The other alternative is, well, not just swapping one kind of single-use plastic with another. Somehow, metal straws have joined the pantheon of reusable water bottles and coffee cups that people trek around, but you know what is already far more readily available? Silverware. Earlier this week, just after tossing my soggy fast-casual bowl to its ominous fate in the trash can, I noticed a clean metal fork sitting on my desk, just waiting for me to use it.

This story is part of the Atlantic Planet series supported by HHMI’s Science and Educational Media Group.