Friday, April 09, 2010

These so-called biodegradable plastics

There's been quite a bit of hype for a few years about corn-based biodegradable plastics. The simple solution to our throw-away culture was to create better things to throw away... or so they say. But the problems with these corn-based plastics run from the obvious to the not-so-obvious.

Photo by Dan Klimke
For starters, they're made from corn. In many instances, it's GMO corn. Even when it's not, corn is the most chemical hungry crop we grow: fertilizer, pesticides, herbicides, you name it. So is it really better than traditional plastic? Maybe. Corn-based plastic supposedly uses less than half the energy that petroleum-based plastics use during production. According to an article by Elizabeth Royte in Smithsonian Magazine, corn-based PLA bags use 65% less energy during production, and emit 68% fewer greenhouse gases than their petroleum-based counterparts. Does that offset all of the chemicals that go into producing the corn as compared to drilling and processing oil? I haven't seen anything conclusive, but oil isn't going to be an option for much longer anyways. If we're going to continue to use plastics (which is another discussion altogether), we have to figure out something, whether corn is that something or not.

My bigger concern is with claims of biodegradability. Companies use this "biodegradable" packaging and present themselves as our saviors. Most consumers, not knowing any better, think this is the greatest thing that has ever happened in the history of mankind. But the fact of the matter is that PLA requires high-temp municipal and commercial composting facilities. These don't exist in most places, and a home compost bin just won't do. Home compost bins are aerobic, and they just don't get hot enough to break down these pseudo-plastics.

There are some exceptions, of course. There are a few producers of bioplastics that claim their products are compostable in a home composting bin. However, of these relatively few manufacturers, I've only found one that has actually been certified as home-compostable. That is Mater-Bi. Mater-Bi was tested by Which?, a UK consumer organization, and found that Mater-Bi composted under normal home composting conditions. The Village Bakery has been using Mater-Bi to package their organic breads since at least early 2008. We could use more companies with that kind of initiative.

Of course, the better solution would be to use no plastic at all. Buy from farmers markets where you can avoid packaging altogether, or grow your own food. Ideally, I wouldn't have a trash bin. I wouldn't even have a recycling bin. I'd only have what I could personally put into my body, compost, or reuse. The prevalence of urban sprawl and the dominance of big agriculture remain major obstacles to this goal. In the evolution to that ideal however, biodegradable plastics have a role to play. Perhaps we start with home-compostable corn-based plastics like Mater-Bi. From there we shift from corn to less chemical-dependent crops. As we lessen our dependence on corn we can diversify the crops being grown on those lands, and perhaps provide all of our food locally. Once foods are grown locally, our excuses for packaging them will disappear.

It's a dream, but a dream worth having.

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