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Comment by RegularOpossum | Hacker News Reader

I expect this to be the start of a trend based on my own personal experience. I bought some "compostable" bags for my kitchen scrap bin that I would then dump in my outdoor composter. Six months later when I went to get my compost, large pieces of bag not only remained but had harded into solid chunks. Took an hour to sift out the chunks from the compost.

Edit: turns out I was ignorant of how they actually work.

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How large is your composter? Many of the "bio-plastics" require high heat composting to decompose, and even then may require a large amount of time. Unless you've got a massive compost pile with adequate aeration and turning, almost no bio-plastics will truly decompose at home.

From the EPA[0]:

> If a plastic product is labeled “compostable,” can I add it to my home compost pile?

> No. Unless the label indicates that the product is okay for home composting, you should not try to compost it at home. Plastic that is labeled as compostable is generally intended to be sent to an industrial or commercial composting facility which has higher temperatures and different breakdown conditions than those found in a typical homeowner’s compost bin. If your community has a residential compost collection program, check with your local government or recycling company to find out if they will accept compostable plastic under this program.

[0] https://www.epa.gov/trash-free-waters/frequently-asked-quest...

Ah that makes sense. I recall the bags I purchased were marketed for home use, guess I got had.

Using them as bin liners at home is fine, the difference is about where they go when you're done using them: home composting or industrial composting?

Perhaps the labeling you saw was intended to be about use, but it looked like it was about disposal?

I thought compostable plastic bags only worked in commercial composters? I probably wouldn't use those in a home situation. But your home situation, you're kind of lucky, because you can just go dump the bin in your compost pile at anytime, and aren't waiting for a pickup or anything.

Yes, during warmer months I just food scraps into my tumbler and I put yard waste in a separate setup. However, during the winter the tumbler ices up and opening it becomes a process.

A good rule of thumb is that truly compostable bags are almost completely useless as bags in the real world. They're just barely good enough to carry the scraps from the kitchen to the compost bin but they won't work as a liner for more than a few hours in the presence of moisture.

The normal way people solve this is with materials that require a small amount of heat to break down in addition to moisture. Industrial composting facilities run at 120-140F.

But yes, these don't break down with home composting which is almost always much lower temperature.

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