"What really is compostable plastic? Who decides what is or isn’t compostable? And what is California doing about it?" --Maia Cavagnolo, 7th grade
Compostable plastic is a wonderful invention, until you look behind the scenes. What really is compostable plastic? Who decides what is or isn’t compostable? And what is California doing about it? Dive into this article to find the answers to these elusive questions, and learn what compostable plastic really is.
Before reading on, there are some important things that differentiate compostable plastic. All plastic is degradable, but degradable plastics need chemical assists to complete the process. This is because tiny fragments of plastic can’t return to nature. Compostable plastic can naturally degrade into water and carbon dioxide into a compost pile, but this process is usually done in industrial facilities. Not all compostable plastic can be decomposed at home. Once the plastic is composted, nothing will remain of it. Biodegradable plastic is like compostable plastic, though it takes longer to decompose, and can leave residue that is harmful to plants, and animals.
“Biodegradable plastic is defined by its ability to break down completely into substances found in nature, and in a reasonable time frame. This sounds good in theory, but in practice, doesn’t often work. While compostable plastic also biodegrades, it is specifically designed and tested to be processed in either home or industrial composting facilities. Compositing facilities enable specific conditions like temperature and moisture to turn the plastic into usable soil conditioner,” says World Wildlife (WWF) in an article on their website.
Essentially, most compostable plastics are built to be composted in industrial facilities, not at home. It can be hard to tell how something has to be composted.
“People are confused by the labels, and struggle to work out what goes where,” wrote Phoebe Weston, in their Guardian article. The “compostable” symbol you see on some bags could mean anything; especially now that businesses see it as an opportunity to sell more expensive products.
“The growing trend in plastic use is fueled by the assumption that if a product or its packaging is labeled as “biodegradable” or “compostable,” then it must be the more sustainable option. Unfortunately, that is not necessarily the case,” states WWF.
Since most “compostable” plastic bags have to be composted in an industrial facility, you can only compost a “compostable” plastic bag at home if it is clearly labeled that way. So, for most “compostable” plastics, you actually can’t compost them at your own house.
Weston backs this up. “Most plastics marketed as ‘home compostable’ don’t actually work, with as much as 60% failing to disintegrate after six months, according to research. An estimated 10% of people can effectively compost at home, but for the remaining 90% of the population the best place to dispose of compostable plastics is in landfill, where they slowly break down, releasing methane, researchers say. If compostable plastic ends up among food waste, it contaminates it and blocks the recycling process,” Weston writes.
Many people are talking about the fact that compostable bags can be 100% biodegradable, but still can’t be composted.
“The label biodegradable can be misleading because many of us assume this to mean we can toss it on our garden heap and it will vanish naturally but more often than not, it means that it can only be composed industrially,” Emmanuelle Gamage writes, “If bioplastics were to end up in the ocean, they would break down into tiny pieces similarly to traditional plastics.”
Biodegradable plastic is not necessarily good for the environment. Gamage continues that, “Bioplastics are plastics made from partly biological matter and biodegradable plastic are plastics that can be completely broken down by bacteria (in a reasonable timeframe in specific conditions). Although made from plant-based substances, biodegradable plastics don’t always break down 100% to their natural form, sometimes they leave residue behind.”
So with all these odd rules about what counts and doesn’t count as compostable plastic, how do you know what to put where?
According to says CalRecycle, “A compostable plastic bag must meet the following labeling requirements:
-Be labeled with a certification logo indicating the bag is certified to ASTM D6400-19.
-Shall not display a chasing arrow resin identification code or recycling type symbol in any form. -Be labeled in accordance with one of the following:
-The bag must be a uniform color of green and be labeled with the word ”compostable” at least one inch in height on one side of the bag.
-The bag must be labeled with the word “compostable” on both sides of the bag with a one-inch in height green color lettering or green color band with contrasting lettering.”
“Beginning January 1, 2026, all compostable consumer products must be made of materials that are allowable agricultural organic inputs under the USDA National Organic Program requirements,” they continue. They plan to enforce what counts as compostable plastic by making a strict code that you must follow if you want to sell, or buy, compostable plastic.
In the meantime, what’s the best thing to do? Bottom line, compostable plastic degrades like other plastic, and it isn’t any better for the environment. Instead, using less plastic will have to do for now. You can drink out of a reusable water bottle, and instead of throwing away plastic bags you can wash and use them again. Learn about how to recycle. Learn about trash sorting, and what a big impact such a little thing can have on the environment.
Before reading on, there are some important things that differentiate compostable plastic. All plastic is degradable, but degradable plastics need chemical assists to complete the process. This is because tiny fragments of plastic can’t return to nature. Compostable plastic can naturally degrade into water and carbon dioxide into a compost pile, but this process is usually done in industrial facilities. Not all compostable plastic can be decomposed at home. Once the plastic is composted, nothing will remain of it. Biodegradable plastic is like compostable plastic, though it takes longer to decompose, and can leave residue that is harmful to plants, and animals.
“Biodegradable plastic is defined by its ability to break down completely into substances found in nature, and in a reasonable time frame. This sounds good in theory, but in practice, doesn’t often work. While compostable plastic also biodegrades, it is specifically designed and tested to be processed in either home or industrial composting facilities. Compositing facilities enable specific conditions like temperature and moisture to turn the plastic into usable soil conditioner,” says World Wildlife (WWF) in an article on their website.
Essentially, most compostable plastics are built to be composted in industrial facilities, not at home. It can be hard to tell how something has to be composted.
“People are confused by the labels, and struggle to work out what goes where,” wrote Phoebe Weston, in their Guardian article. The “compostable” symbol you see on some bags could mean anything; especially now that businesses see it as an opportunity to sell more expensive products.
“The growing trend in plastic use is fueled by the assumption that if a product or its packaging is labeled as “biodegradable” or “compostable,” then it must be the more sustainable option. Unfortunately, that is not necessarily the case,” states WWF.
Since most “compostable” plastic bags have to be composted in an industrial facility, you can only compost a “compostable” plastic bag at home if it is clearly labeled that way. So, for most “compostable” plastics, you actually can’t compost them at your own house.
Weston backs this up. “Most plastics marketed as ‘home compostable’ don’t actually work, with as much as 60% failing to disintegrate after six months, according to research. An estimated 10% of people can effectively compost at home, but for the remaining 90% of the population the best place to dispose of compostable plastics is in landfill, where they slowly break down, releasing methane, researchers say. If compostable plastic ends up among food waste, it contaminates it and blocks the recycling process,” Weston writes.
Many people are talking about the fact that compostable bags can be 100% biodegradable, but still can’t be composted.
“The label biodegradable can be misleading because many of us assume this to mean we can toss it on our garden heap and it will vanish naturally but more often than not, it means that it can only be composed industrially,” Emmanuelle Gamage writes, “If bioplastics were to end up in the ocean, they would break down into tiny pieces similarly to traditional plastics.”
Biodegradable plastic is not necessarily good for the environment. Gamage continues that, “Bioplastics are plastics made from partly biological matter and biodegradable plastic are plastics that can be completely broken down by bacteria (in a reasonable timeframe in specific conditions). Although made from plant-based substances, biodegradable plastics don’t always break down 100% to their natural form, sometimes they leave residue behind.”
So with all these odd rules about what counts and doesn’t count as compostable plastic, how do you know what to put where?
According to says CalRecycle, “A compostable plastic bag must meet the following labeling requirements:
-Be labeled with a certification logo indicating the bag is certified to ASTM D6400-19.
-Shall not display a chasing arrow resin identification code or recycling type symbol in any form. -Be labeled in accordance with one of the following:
-The bag must be a uniform color of green and be labeled with the word ”compostable” at least one inch in height on one side of the bag.
-The bag must be labeled with the word “compostable” on both sides of the bag with a one-inch in height green color lettering or green color band with contrasting lettering.”
“Beginning January 1, 2026, all compostable consumer products must be made of materials that are allowable agricultural organic inputs under the USDA National Organic Program requirements,” they continue. They plan to enforce what counts as compostable plastic by making a strict code that you must follow if you want to sell, or buy, compostable plastic.
In the meantime, what’s the best thing to do? Bottom line, compostable plastic degrades like other plastic, and it isn’t any better for the environment. Instead, using less plastic will have to do for now. You can drink out of a reusable water bottle, and instead of throwing away plastic bags you can wash and use them again. Learn about how to recycle. Learn about trash sorting, and what a big impact such a little thing can have on the environment.