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[greenyes] FW: [greenyes] recycling vs. composting of cardboard


Thanks for the important info on the gable top milk cartons having a plastic
coating today, rather than the wax of old. I also agree with you that
refillable glass is a good option - in fact it's best when available.

As for the plastic jugs, though, I advise use of the nearly universally
recyclable #2 HDPE polyethylene jug over polycarbonate, and here's why:

HDPE is comprised of pure polyethylene, a polymer that is chemically simlar
to paraffin wax, but only different from it in terms of the structure of the
molecule (polyethylene is highly linear or somewhat branched, with very long
molecular chains, while paraffin wax is made of shorter chains of a highly
branched configuration). These differences in shape give the two materials
somewhat different physical properties, but the chemical properties are very
similar -- especially in terms of chemical inertness, because paraffin and
polyethylene molecules are comprised only of saturated C-C and C-H bonds,
which are relatively unreactive.

On the other hand, I have reservations about polycarbonate, because the
thermoplastic version -used in bottles - is nearly 100% made from bisphenol
A, a well-known plasticizer which has been shown to be an endocrine
disrupter. The other ingredient in making polycarbonate is phosgene, a WWI
poison gas -- but the dominant material is bisphenol A. The industry claims
that no free bisphenol A remains after the polycarbonate is processed, but
I'm not sure we should trust them. We have certainly been led down the
garden path on the question of the safety of plastics before. What specific
studies support that assertion? I've looked but have yet to find any. Can
anyone provide citations?

Furthermore, I'm not sure that the breakdown characteristics over time of
polycarbonate have been fully studied -- what are the effects of
temperature, sunlight, and pH, in different combinations? Polycarbonate
contains repeating units of esters and benzene rings on its structure, which
should theoretically provide chemically reactive sites, even if you forget
about possible bisphenol A contamination.

Like many, our twelve year old daughter is enamored with the lovely colored
polycarbonate water Nalgene bottles that are now everywhere, but we have
encouraged her to use the HDPE versions that aren't so crystal clear, but
may be more stable. It's the way we put the precautionary principle to work
at home.

Anne Morse

-----Original Message-----
From: EarthGB@no.address [mailto:EarthGB@no.address]
Sent: Saturday, June 12, 2004 2:37 AM
To: calcompost@no.address; greenyes@no.address
Subject: Re: [greenyes] recycling vs. composting of cardboard

In a message dated 6/3/04 8:02:50 PM, calcompost@no.address writes:

<< For a while I've been buying milk in waxed cardboard 1/2 gallons, &
composting the carton. I've noticed that it takes quite a while to
decompose, and
it appears I'm ending up with a plastic coating in my compost. Any

It was my intent to reduce my waste & environmental impact by purchasing
in the cartons, rather than using milk in #2 plastic jugs. Am I wrong?


Dear Angie,

About composting milk cartons, the fact is that these and all frozen food
packages, cold drink cups, etc, are made of polycoated paper, that is,
paper coated on both sides with low density polyethylene (LDPE) plastic, NOT

wax as many people believe. Hence the plastic ending up in your compost.

I'd suggest that you buy milk in high density polyethylene (#2 HDPE) jugs,
which are almost universally collected for recycling. This will remove the
plastic source from your compost. If you don't want to buy milk in the most

common HDPE bottle, then I think your choices are (1) look for milk supplied
returnable glass bottles; or (2) see if any local milk suppliers offer milk
polycarbonate (PC) plastic bottles. The latter are returnable, refillable,
recyclable, but offhand I don't know how widely available they are.

PC bottles are like the large blue tinted bottles used for many water
coolers. PC would be coded #7. It's a high-end engineering plastic with
good reuse
potential given the quality of the plastic & its value. However, you may
to search around to see if a local dairy offers the bottles & has take-back
in place. PC is a more stable plastic that won't impart a plastic flavor to

bottle contents. I've been reusing PC bottles for my water cooler for years

with no problem. Before I take them back to refill at the water store, I
around a few drops of hydrogen peroxide in the bottles, then pour them out.

That sterilizes the bottles.

I can only offer my opinion regarding composting vs recycling of corrugated
cardboard, namely that I think recycling is the preferred option to save

forests, etc. Corrugated is eminently recyclable, with many mills accepting
it at
good prices. If your local recycling collection program does not accept

corrugated, you should lobby them to add it, as it's a large fraction of the

Good luck,
Gretchen Brewer
Earth Circle
San Diego, CA

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