Just yesterday I went out to do the week's composting. As usual I
dug a hole in the center of the pile where the discarded food and
food paper from a week would go. At the bottom of the hole was the
remains of a compostable plastic bag my wife bought to carry leaves
in the front yard to the back for composting. The bag had been green
and about 90% intact when I put it on top of last week's food
offerings and covered it with new plant trimmings to keep the
critters out. Now it was only about 20% there and what remained was
quite shredded and had turned a dark gray. By next week it will be
I've also composted other types of compostable bags with similar
results. And a couple of years ago after a recycler's party I
composted some hard plastic forks and knives that were corn-based
polymers. All gone, no trace.
There's a lot of hyperbole out there in the world. I've heard from
such "authorities" that corn-based polymers require high heat to
compost and so won't compost in a relatively cool backyard pile.
Baloney! Tell it to the worms, the sowbugs, the millipedes, the
fungi, the bacteria that live in my low-heat compost digester and
that make short work of such "food-grade" polymers.
It's the petroleum-based polymers that are resistant and show up as
plastic litter when I break down my piles to liberate all the good
humus that has been created so it can be sequestered from the
atmosphere into the soil of my garden. Even that plastic litter
shows signs of degradation, but I pull it out and send it to
landfill, making a mental note not to use such products if I can help
Try it yourself.
I have no idea who Martin Hocking is, but there are many scientists-
for-hire out there who do get grant money from plastics manufacturers
and whose learned-sounding opinions are worth about as much as
plastic litter. The plastics industry has been one of the biggest
and most persistent sources of misinformation and disinformation
about their product plague for decades now.
Dan Knapp, Ph.D.
CEO, Urban Ore, Inc., a Berkeley-based reuse and recycling company
On Dec 17, 2007, at 6:56 AM, Peacemonger wrote:
I just did a search on this forum and found that my question was
addressed about 18 months ago, but I was wondering if there was any
new information out there on this.
Last summer I was helping to plan bible school at my church. My
church uses, mostly, Styrofoam cups. When I was researching other
options, including compostable plastic, I ran across Martin Hocking's
research regarding the intrinsic energy cost of various forms of
disposable and reusable products. I wrote to him and he sent me
information about several studies he had done and it sounded like the
Styrofoam was the least problematic option for my church. However,
over and over again Styrofoam makes the top 10 lists of things to stop
using to save the planet on the websites of various environmental
My county has an award winning composting program, but it accepts only
yard waste at this time. I've been told that even the best back yard
composting can't manage compostable plastics made from corn. So I'm
assuming, aside from the lesser amount of petroleum used in
manufacture, using compostable plastic isn't much of an improvement.
Martin Hocking said that the amount of energy used in making reusable
dinner wear is high, the energy used in washing it is high, and the
energy used in disposal is high, so in a situation like a church
fellowship hall with lots of children, reusable dinnerware isn't a
good option. The church also doesn't own a dishwasher, so that might
be a problem. I had considered having folks bring a cup to use each
night, to at least cut down on the cups. I suspect that this would be
a hard sell because people would forget to bring them, or forget to
take them home, and I think that would be seen as a big inconvenience.
One option I considered is that there is a salvage grocery store near
here that sells cups and plates from local restaurants that the
restaurant isn't going to use. They have super bowl plastic cups long
after the super bowl and things like that. Most all of them are paper
cups with some sort of wax coating or they are the #2 plastic cups.
Dr. Hocking's response was, "If half a dozen china cups/mugs are
chipped or broken during the Bible School, then each one is equivalent
in terms of energy cost as about a thousand polystyrene foam
disposable cups. The washing energy for a glass or china cup is about
the same as the energy required to make and dispose of a polystyrene
foam cup. Paper cups have a greater intrinsic energy cost than
polystyrene foam, but still much less than a china cup would, so could
also be used as a substitute."
He gave me these references:
Hocking, M.B. 1991. Paper versus polystyrene, a complex choice.
Science, 251 (4993), 504-505.
Hocking, M.B. 1991. Relative merits of polystyrene foam and paper in
hot drink cups: Implications for packaging. Environmental Management
15 (6): 731-747.
Hocking, M.B. 1994. Disposable cups have eco-merit. Nature 369, 107,
Hocking, M.B. 1994. Eco friendly cups? Nature, 371: 481-482, October
Hocking, M.B. 1994. Reusable and disposable cups: an energy-based
evaluation. Environmental Management 18 (6): 889-899.
So what do you think? Can I compost the plastic in a backyard
composter or will it just hang around in there forever? Are the cups
from the restaurants good options because they would go into the trash
if some group like my church didn't use them? Is there any benefit to
having people bring their own cups? Does the Styrofoam have as small
an impact as Dr. Hocking suggests? Is he receiving funding from Dow?
Perhaps my best bet is to leave the church alone and start a letter
writing campaign to the county to upgrade the composting to include
Any suggestions you have will be appreciated!