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Many recycling programs don't accept #2 (♴ - high-density polyethylene - HDPE) plastic bags (only #2 rigid plastic). Does the same apply to #4 (♶ - low-density polyethylene - LDPE) plastic? I've seen it both in rigid and film form and I'm wondering if the reasons for not accepting #2 film apply to #4 film.

Alternatively, if I can return #2 plastic bags to a grocery store, can I also reliably return #4 plastic bags to a grocery store?

  • What do those numbers refer to? – gerrit Aug 19 '14 at 22:52
  • @gerrit, The numbers correspond to what's inside the recycling symbol printed on the bag – drs Aug 19 '14 at 22:55
  • Or avoid plastic bags all together. We use cloth bags most of the time now. – Sherwood Botsford Aug 6 at 4:02
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I think what is accepted at stores or recycling centers is very much local policy and depends on both regulations (local law) and the way collection and recycling schemes are setup and funded. In the Netherlands where I live for example, all types of packaging plastics including bags, but excluding other plastic objects and biodegradable plastics, are collected via communal collection schemes. The reason why they choose for all packaging plastics is that manufacturers are required by law to collect this.

The types of plastic you are referring to are #2 High-Density PolyEthylene (HDPE) and #4 (Low-Density PolyEthylene (LDPE). HDPE is relatively easy to recycle and is also the most recycled type of plastic. LDPE on the other hand often isn't recycled. How difficult it is to recycle a plastic depends on the resin type, but also on if it's contaminated with dyes and other chemicals.

In order to recycle a plastic properly you need to separate the different types of plastic and remove contaminations as much as possible. I suspect that in your case policy is to gather only 1 specific type of plastic object so separating is less of an issue for the recycling center (to reduce costs). Whether or not you can safely return #4 plastic bags to a shop depends on what the shops do with it and if the plastic types are properly separated.

EDIT: according to this curbside recycling program they don't accept plastic bags because their equipment can't handle it properly. On a different webpage they also say that

Don’t be fooled into thinking that all (or even most) of the plastic collected by those programs is actually recycled! There are very few domestic (U.S.) markets for plastics numbered 3 through 7. China, one of the principal foreign markets for U.S. plastics, has recently undertaken measures to stem the influx of non-recyclable and contaminated materials hitting their shores. At least for now, “the markets for #’s 3-7 plastics have dried up!” ...... The bulk of post consumer plastics #3-7 collected in this country have always gone oversees, primarily to third world countries where environmental controls and worker safety standards are far inferior to those in the U.S. (source)

So my guess is that most #4 plastic, no matter the form is either shipped oversees, dumped on landfills or burned.

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Film has the following issues for recycling:

  1. It's not well labeled. (Which bin should it go into?)
  2. It's irregular in shape. (Makes automated separation difficult)
  3. The weight per piece is small. (It takes about the same time/energy/computer power to pull a small chunk from a waste stream as a large chunk)
  4. The ratio of dirt to plastic tends to be high. A milk carton is easy to rinse. Getting the bread crumbs out of the bag is tougher. (Think in terms of automated equipment.

One of the more common uses of mixed plastic feed stocks is to make synthetic fence posts. Mix up wood chips and molten plastic, and extrude. The resulting product is not as strong as an all wood post, but is considerably more rot resistant. If the source material is chipped pallets then the entire product is recycled. The resulting product is about 1/4 to 1/3 plastic, is not noted for its beauty, and is difficult to paint.

There have been attempts to make decking out of this blodge material, but I've read of problems with warping, surface finish.

(This should be a comment, but it is too long, and comments do not allow formatting.)

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