Friday, August 24, 2012

A Review/ Experiment/ Story of Compostable Bags

I peeled back the gift wrap and politely smiled, trying to hide the confused look on my face. Why in the world would I need “compostable bags”?

The first half of the gift was a beautiful new stainless steel kitchen collector. The kind all my composting friends envy when we hang out in my kitchen (which is surprisingly often). I know the new collector is fancy dancy but does it really need protection from my banana peels and apple cores?

After sincerely thanking my brother and his wife, the sparkly new bucket won a prize spot on my counter while the bags sat unused in a drawer for six months. In June my inner scientist found the forgotten bags and became curious. I wonder if these bags made of “compostable plastic” really work?

So for a month I conducted an uncontrolled, relatively unscientific experiment. I lined the bucket with the bags and dumped the contents, bag and all, into my compost bin.

Did they work?

Observations/ Results
Let me preface my results section by saying it has been a very dry summer in Cincinnati. And I’ve been very busy, so I have not watered or turned my bin nearly as much as my dutiful composter side would have liked.

When I turned the bin last weekend, I found bags that had been composting for about two months. More they found me because they kept getting stuck on the end of my pointy metal compost aerator. It was only mildly annoying pulling the bags off.

Inside the bags I observed the food scraps had completely composted into fine humus matter (i.e. my banana peel turned into dirt). Of course, since one of the joys of composting is witnessing the transformation, seeing this change on a small scale was fun. This would be great way to show children what is happening in the compost bin.

However, this also demonstrates that the bags were still intact. At least until my compost turner impaled them.

I still believe they will eventually break down. The material was noticeable thinner and more stretchy. And now that they are torn apart, sitting in a watered and turned pile, they have the optimum environment for composting.

It’s still too early to tell, I may have to follow up in a few months to give you an update (I know, the anticipation is overwhelming…). But here are my preliminary pros and cons of using compostable bags for backyard composting:

Did not have to clean the collector after emptying
Every scrap of food went into the composter
Fun to see food scraps composting on a small scale

Bags cost money (not my money, but still…)
Bags did not compost as quickly as food scraps
Bags got stuck on the compost turner

If food scraps really gross you out or you take out your kitchen collector infrequently, bags may be helpful to you. However, in the future I think I'll stick to rinsing out the bucket or using the fun origami newspaper trick.

Still, I’m interested to hear from you. Have you ever tried compostable bags? How did they work?


  1. A year or so ago somebody came out with snacks in supposedly compostable bags. Awful. They were semi-metallic so real noisy (crinkle crinkle SHUT UP!!) and do not compost - if they do they have a half life of 3 brazillion years. Sounds like the same as whatcha got there Michelle.

    1. Maybe, I think these are a lot thinner so I really hope they decompose and I'm not stuck pulling pieces our of my finished compost like I did with the "compostable" cups I bought a few years ago.

  2. I also tried the compostable bags last year. I used a plastic coffee can ( dont know if I can use brand names so Ill just say the red one and it was the biggest one) and I thought the bag would prevent the container from absorbing odors. The bags were convenient and after a week they did not leak. While good, I was suspicious. The bags did not compost quickly and got caught on the compost turner. I pulled out the bags and put them in a separate pile thinking that sun would help. It still took several months for them to break down and I still find some strips of material even a year later. I used the origami and that is so much better!

    1. That seems to be what many people experience. Perhaps the manufacturer design them more for commercial composting operations than backyard bins.

      I'm glad the origami trick is working!

  3. Hey great topic and one near and dear to me. One thing to know is almost all compostable liner bags on the market are not designed to break down below 140 degrees. Therefore most backyard composts don't maintain that temperature and the bags take alot longer to compost. I've tried these in my own composter for years and found that to be true. We at EcoSafe just launched a home-compostable bag that I tried myself the last few months and they do break down alot quicker. That doesn't address the issue of cost and the aerating issue but my view is if a home-compostable bag will get more people to compost where the yuck factor is the reason they don't then it is a good thing. I'm also working on a new product that will be another option as well that will hopefully get even more people composting their food scraps.

    1. Thanks for the explanation, Doug, that's good to know.

  4. I haven't used the compostable plastic but have tried to compost the "compostable #7 PLA" plastic before (PLA = poly lactic acid, made from corn). I ripped it up into shreds, and even with proper turning they never broke down, so I eventually pulled them out and tossed them. My composter never gets very hot so I don't think it would ever be able to break them down...

    1. Yeah, I tried some compostable cups with the same problem. I think they are just meant for industrial sized composting operations not backyard bins. ):

  5. I think the words 'compostable' or 'biodegradable' cannot be used with the word 'plastic'. Either the bag is made from corn and is truly 100% biodegradable or it contains plastic which will never truly biodegrade, it only breaks down into smaller pieces of plastic which end up in the oceans and work their insidious, destructive way through the food chain. Come on people - you don't need bags in your kitchen compost bin, just empty the food waste onto your compost bin and give it a rinse out. Laziness and convenience are killing the planet.