Wednesday, March 3, 2010

Corn-Based Plastic -- Vice Masquerading as Virtue

So there you are, tossing your corn-based plastic cup into your corn-based plastic garbage bag and then tossing your corn-based plastic garbage bag into your regular old garbage bin. OK, so it's going to the landfill, but still, it's biodegradable and that makes you all green and virtuous and stuff, right?

Actually, no.


Turns out that compostable plastics are only green if you actually compost them. If you toss them in the landfill, they're not going to decompose any more than a conventional plastic bag will. Or at least you hope they won't. In the oxygen-deprived atmosphere of the landfill, decomposing organic materials produce methane, a greenhouse gas 72 times more potent than carbon dioxide over a 20 year time frame. Landfills are the largest human-made source of methane emissions in the United States, with a greenhouse-gas impact equal to one-fifth of that produced by the nation's coal-fired power plants.

If it's not going to be composted in an industrial-grade composting facility, don't use compostable plastic. Throwing compostable plastic in with recyclable plastic just contaminates the recycling load, and trying to compost corn plastics in your home compost pile doesn't work (home compost piles don't get hot enough). If the garbage is headed to the dump anyway, you might as well use conventional plastic garbage bags. The real low-impact solution: work to eliminate your landfill-bound garbage entirely by composting your food waste, recycling your recyclables, and avoiding products with plastic packaging.


  1. It turns out that methane in a landfill might not be all bad. A new type of landfill is coming on line known as a “Bioreactor landfill.” Bioreactor landfills are designed to enhance biodegradation and the capture of those gases. Since the 90’s, the federal government has mandated that landfill operators capture their biogases (LFG’s). Initially those operators were burning off gases, they’ve since discovered that there is value in those gases and have been using/selling them for the production of clean energy. Landfill operators of conventional landfills are able to capture around 70 percent of the gases produced. Bioreactor landfills will be much more efficient at manufacturing and capturing LFG’s. What an excellent use of our trash….turning it into clean energy.
    “Bottles for a Healthier Earth”

  2. I'm dubious about landfills as an energy source, even though landfill operators are eager to rebrand themselves as a source of green energy. Methane capture is by no means fool proof, and the highest and best use of biodegradable materials is as a soil enhancement, not as an energy source. Composted soil is a potent carbon sink -- but it has to be healthy to do its job.