"COMPOSTABLE" PLASTIC

The International Compost Sanitation Forum and Message Board: General Composting Issues: "COMPOSTABLE" PLASTIC
Author: Herb (Herb)
Sunday, December 13, 2009 - 3:15 pm
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Joe's experiment answers my questions about so-called compostable plastic bags. I'm interested because I use ordinary white plastic (13 gal) bags as "bucket" liners (without the bucket).

This makes me wonder if some kind of "waterproof" paper bag might meet our requirements. They would only have to hold up (not leak) long enough to fill which isn't very long. But I imagine the cost would be very high. What we need is a VERY CHEAP compostable bag.

Author: Nancybeetoo (Nancybeetoo)
Wednesday, June 03, 2009 - 11:17 am
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Hi June,

Kudos to you for intercepting all that poop on its way to the landfill. It breaks my heart every day to see people putting poo into plastic bags and then sending it to the landfill to stew with all the nasty stuff there- household cleaners, old sofas, batteries etc.

I do compost dog waste along with all my other compostables. My bins run 120 to 140 degrees continuously, so I don't worry about parasites, microbial or otherwise.

I am careful about monitoring temperatures with the compost since there are 5 dogs contributing. I am confident my own dog doesn't have worms because I see her poop. I don't know if the other dog owners are as aware of their dogs health.

I have never tested the resulting compost for worm eggs or fecal coliform. Would you be interested in a sample? I fill a bin every 3 to 4 months so I have bins ranging from active (the one I am currently filling) to 4 months, 8 months and 1 year old.

Nancy

Author: Jbaker (Jbaker)
Tuesday, June 02, 2009 - 6:02 pm
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Nancybeetoo-

Do you place your dog doo in your regular compost? Any issues with parasites? I am conducting a dog waste composting feasibility study for the city of Anchorage. Do you have any resources or suggestions for people to talk to that have composted dog doo on a regular basis?

Author: Nancybeetoo (Nancybeetoo)
Thursday, May 07, 2009 - 1:10 pm
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I have been composting dog poop bags from biobag for about a year. My experience is that some recognizable fragments remain after 6 months. Those disappear over time though so it doesn't worry me. Soon I will take apart my one year old pile and see if there are any fragments in it.

Author: Joe (Joe)
Tuesday, May 05, 2009 - 6:04 pm
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Speaking of reusing cups - I have reused plastic cups for years. Just wash them and use them again. Same for plastic bags like zip-locks and plastic cutlery.

Author: Ecointerest (Ecointerest)
Monday, May 04, 2009 - 10:43 pm
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Joe, I have a similar experiment going for 8-9 months, trying to compost some disposable cups, which were used at the Sustainable Living Expo here in Hobart, last year. These cups are made of paper, somehow glazed with a wax or maybe plastic layer.

The rationale was that the paper would break down under the action of forest micro-organisms, including fungi, worms, etc. So I mixed the cups in with a pile of chipped eucalyptus mulch. So far, there has been some decay, but not very much, and certainly not enough to say that you could use this method for a large quantity of cups and plates made of the same material.
My conclusion, which might not be very politically correct, is that maybe we should think about washing reusable cups at the kitchen sink!
Organised correctly, a few people, perhaps hitherto strangers, combine their energies to perform a good, social service and in the process make new friends, new networks. Careful use of water, minimal use of dish detergent, is good education in itself. Some people are happy to reuse their cup for a second serve of coffee, instead of using a new disposable cup. Surely this is a "green" solution.

Author: Joe (Joe)
Monday, May 04, 2009 - 11:37 am
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OK - I posted a year or so ago that I was experimenting with "compostable" plastic bag toilet receptacle liners. I used a few boxes of these bags to line five-gallon toilet receptacles over a period of about maybe 6 months. The bags were dumped into my humanure compost bins. It really helped minimize the cleaning of the toilet receptacles and I could see long-term benefits, especially in large scale systems where many toilet receptacles are being collected on a regular basis.

I should add that I have never had a problem with cleaning toilet receptacles. I use a long handled brush and a little water and a drop of dish soap and brush out the receptacle, then dump the water into the bin. Then I rinse the receptacle and that's all there is to it. It takes a few seconds and is not a burdensome issue for me. However, I can see the potential for liners to be useful, so I experimented with them last year.

This year I broke into my compost pile and was digging around in there taking out compost for the garden and wondering who the hell put plastic in my compost. I kept finding pieces of plastic, having forgotten about my little experiment. It wasn't until I pulled a piece of plastic out of my wheelbarrow load of compost, standing in the garden, that I remembered the plastic liners.

So here's the verdict: the plastic disappeared about 90%. Most of it was no where to be seen. However, there was still some left. Enough that I had to pick it out. Everything I picked out I could have stuffed into a standard size beer can, so it wasn't too bad. I think the plastic liners would work better in larger-scale situations where the compost reaches higher temperatures for longer periods of time.

I won't use them again in my home system, but I may look at them again for a larger-scale system if the price is right and they save water, time and energy. So the verdict is still out on "compostable" plastic, but it looks like there may be some potential usefulness for this product.

Author: Joe (Joe)
Monday, May 04, 2009 - 11:24 am
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From email:

I tossed some cups into my humanure composting at least three years ago. I have pulled them out of the finished compost each year (one compost run per year at Summer Solstice Cycles) and tossed back into the new compost, thus they have been through the compost at least two times. This year I am not returning them and will toss them into the long term brush composting pile or the manure pile. The cutlery has broken down about 50% but the cups are only 20% broken down. Those new compostable hard plastic like plant pots break down faster but still hang in there. A big problem are the cups: as they break down, they become brittle but remain clear to milky and thus create bits and pieces in the garden. I spend too much time sorting the stuff out of the compost. It is important to not put all the cups stuck together as it really slows down the process and pulling them apart once they begin to decompose is very difficult.

In conclusion, I would not recommend tossing that stuff in typical compost bins. Even it they go in the landfill, they are a renewable resource and landfills produce methane from the breakdown of the material that gets used for power.

Author: Joe (Joe)
Monday, May 04, 2009 - 11:24 am
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I have started this thread to deal with the topic of compostable plastic bags, cups, dinnerware, bowls, etc. What have you experienced? There is some discussion about this topic in other threads, especially about compostable plastic bag toilet receptacle liners. If we consolidate the discussion in this thread, it will be easier for someone to find should they be searching this message board.

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