Re: [GreenYes] Are degradable plastics zero-waste?
Doug Koplow
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Doug Koplow
Earth Track, Inc.
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Cambridge, MA 02140
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>>> "SPENDELOW Peter H" <SPENDEL...@deq.state.or.us> 04/03/06 06:12PM >>>
To the GreenYes list:
The GreenYes List has a lot of zero-waste advocates as members, so I thought to an appropriate place to raise this issue.
There is a conference in Minnesota this Thursday and Friday (April 6-7) that will look at bio-based plastics. Bio-based plastics are plastics made using feedstocks from renewable organic molecules such as starches and sugars. A prominent bio-based plastic is PLA (Polylactic Acid), which is formed by fermenting sugars from corn to form lactic acid, and then polymerizing the lactic acid into a plastic.
I have been seeing discussion from some people indicating that use of bio-based degradable plastics is in keeping with zero waste principals, because when you are done with the items made from PLA, you can compost them back into carbon dioxide and water.
I am hoping to spark some discussion on whether composting PLA is really zero waste. When I look at the web site of the Zero Waste Alliance (http://www.zerowaste.org/case.htm), I see that their Zero Waste goal lists "zero waste of resources" as its first goal, followed by zero waste to landfill and zero waste of other things (hazardous waste, emissions, etc).
Composting PLA might meet the "zero waste to landfill" criteria if you don't look at the solid wastes created in the production of the PLA, but how well does it fare on "zero waste of resources" issue? As far as I can tell, it fares poorly. When you compost PLA, you get nothing useful out of it - only carbon dioxide and water. You don't get any significant amount of "compost". Compost is valuable product for restoring organic matter to soils, and consists mainly of complex organic molecules derived from partially-decomposed lignins from wood and other plant matter. When you compost leaves, grass, and wood, you get "compost". Put PLA in the compost pile though and my understanding is that the PLA will decompose almost completely into carbon dioxide and water, and not add anything appreciable to the compost.
Thus, when you compost PLA, you get nothing of value out of it. All of the work and energy that went into growing the corn, milling and isolating the sugar and starches, fermenting them to produce lactic acid, and then polymerizing them to form PLA - all of that is lost. All of these inputs require fossil fuel - to produce the fertilizer, run the tractor, and do the chemistry to produce PLA. For that matter, based on Cargill-Dow's life cycle analysis, it currently takes almost as much fossil fuel to produce PLA as it does to produce common commodity-grade plastics, and it takes more fossil fuel energy that the amount of petroleum embodied in an equivalent amount of polyethylene plastic. Cargill-Dow is working to reduce this fossil fuel requirement, but they are not there yet.
In contrast, recycling or reusing the PLA should save considerable resources. PLA is a thermoplastic, and it should take a lot less energy to make a PLA item out of recycled PLA than it does to make it out of corn sugars. Even burning PLA as a fuel should at least save the energy embodied in the plastic itself. PLA should burn very cleanly in a large industrial boiler.
The only time I can see value in composting PLA is when PLA is used in a manner that makes the composting of other materials easier, or where no recycling or energy-recovery option is present. Examples include PLA bags used for collecting food waste or yard debris for composting, or possibly plates and utensils used in schools and institutions that compost their food waste.
In contrast, making water bottles out of PLA and then composting those water bottles doesn't seem very "zero waste" to me.
So - all you zero waste advocates out there - what do you think about how degradable plastics fit in with the Zero Waste vision?
Peter Spendelow
Oregon Department of Environmental Quality
503-229-5253
SPENDELOW Peter H
I don't know about other bio-based plastics, but polylactic acid (PLA) does not break down quickly as litter or in water or in small home composting piles. Paper items break down much quicker. PLA requires both moisture and heat to break down. It does break down fairly quickly in commercial composting, because the commercial composting piles get pretty hot and also have sufficient moisture present. It will break down eventually though, which certainly is a good thing for littered items that do not get picked up.
Peter Spendelow
Oregon Department of Environmental Quality
503-229-5253
Eric Lombardi
This is exactly the kind of debate the Zero Waste community needs to be
having right now regarding biopolymers. I support them for many reasons,
but that doesn't mean there aren't issues to be dealt with... and in my mind
the primary one right now is the "recyclability" issue versus the
"compostability" issues.
I asked my resident composting expert about what you said and here was his
answer:
"I can't verify that PLA breaks down into CO2 and water, but it appears
Peter has done some homework so I'll take his word for it. No compost
facility manager will be seeking out a PLA feedstock for the value it gives
to the compost - that's safe to say. But I think Peter's criticism should
be with the marketing angle Cargill has taken, not the ZW movement. What he
considers to be the "only" value of PLA is to me the key to ZW - that it
makes the composting of other materials (food waste) easier. He's talking
about a quarter of the waste stream - that's a pretty big "only"! For the
purposes of the ZW programs that we have in place, PLA is the difference
between success and failure. So, the PLA marketers want to sell to
companies like Biota that would otherwise use recyclable containers - if
Peter is right that PLA compares favorably to plastic in its recyclability,
then we are absolutely on the right track in pressing Cargill to come up
with a recycling solution for it. Zero Waste does not mean zero sum energy
use to me. Everything we do takes energy that we don't get back...until
we're powered by renewables!"
So, at Eco-Cycle we have experienced first-hand the power of using
biopolymers with food services at public events, and it is a powerful
demonstration of how design and a little effort can get mixed organic waste
out of the landfill, thus protecting groundwater and air quality. The public
loves the idea, learns more about "composting" and it's values in five
minutes than they've learned during their whole lives (why? Because they are
so CURIOUS about the biopolymers that their minds open up and embrace the
new information!)
Anyway, I think your points are well considered and this sort of dialogue
needs to keep happening so that Cargill and the rest of them LEARN FROM US
what the key issues are as this industry grows.
Eric Lombardi
Executive Director/CEO
Eco-Cycle Inc
Boulder, CO. USA
303-444-6634
www.ecocycle.org
poweredbysweat
and tried to compost them in my home compost pile. The second time I
dug in the area, I found the containers still mostly intact, but
covered with little maggot-like creatures. The third time I dug in the
area (about a month between digs), the containers were mostly gone.
Every once in a while I find a little piece that probably wasn't
buried. I'm not too concerned about getting more than carbon out of
the containers in my compost.
If one is really concerned about not getting as much carbon out of
compost, one would compost leaves before they turn brown in the fall.
I do this quite a lot - harvest green leaves for composting around
frost-time.
Jim Gagnepain
http://home.comcast.net/~oil_free_and_happy/