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Why Can’t I Compost All Plastic Labeled “Compostable”?

By Recyclebank |

Many bio-plastic products claim to be compostable, but what does that really mean for disposal? Find out!


Updated On 07/10/2018 | Originally Published On 04/23/2014

Dear Recyclebank: I recently came across some plastic cups that are labeled “Compostable and Biodegradable”. Can I really throw so-called biodegradable plastic into my compost pile? –Brenda L.

Dear Brenda: It sounds too good to be true, doesn’t it? After all these years of seeing plastic cups littering the landscape and hearing about how environmentally damaging they can be, a biodegradable and compostable plastic cup sounds like a miracle.

While it is true that some plastic cups are compostable, it’s likely that they’re not compostable in your backyard. Certified-compostable plastic cups are designed to break down in commercial composting facilities only. That’s because these facilities maintain the conditions needed for the plastic to break down, which isn’t likely achievable in your backyard. The compost pile in your backyard, or even your rotating bin if you have one, is unlikely to reach or maintain the heat, aeration, moisture, and chemical balance necessary to biodegrade the plastic. So if you put that cup in your pile, there’s a good chance it’ll still be there years later.

Compostable plastic is also not recyclable in the traditional sense, which puts it in a kind of limbo in terms of disposal. As yet, commercial composting facilities are not widespread, which means until they become widespread, most biodegradable plastic will go to a landfill, where it won’t actually biodegrade much, due to the lack of oxygen in landfills.

This goes for compostable plastic bags as well. Bio-plastics will not break down if tossed in the trash and sent to a landfill. In fact, many things don’t break down adequately in landfills, or they do so very slowly, because of the lack of oxygen. Bio-plastics also won’t just melt back into nature if thrown outside, which is why these labels can actually cause problems if people think that’s the case.

Truly biodegradable plastic cups are an advance for our environment, but only if they are properly processed. The requirement of very specific conditions to break down compostable plastic means that the environmental advantages of compostable plastic cups will not be realized unless they end up at a commercial compost facility.

Ask you hauler if they accept compostable or biodegradable cups before putting them in your curbside recycle.


One big drawback of bio-plastics is that they can’t be included with current plastic recycling. Send plastic cups labeled “compostable” to commercial composting facilities where available. Some haulers are set up to do this for their customers. Otherwise, these cups must go in the trash.


Better yet, press your local government to institute commercial composting in your city! One useful talking point is that commercial composting operations create twice as many jobs as landfill operations do!


The more widely adopted commercial composting gets, the more opportunities we’ll all have for a truly compostable plastic.


SOURCES: Biodegradable Products Institute, US Federal Trade Commission, US Composting Council


Did you know that not everything labeled “compostable” can be composted at home?


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