vendredi 30 janvier 2009

Biodegradable corn cups: Too good to be true?

Via Examiner

"This cup grew up in Blair, Nebraska. It's made entirely of corn. It's 100% compostable. It will disappear no matter what you do with it."

If you go into one of Boloco's several locations in the Boston area and order a drink, that's what your cup will say.

Formerly known as The Wrap, Boloco is a beacon of sustainability in a city full of fast food that's bad for you and the environment. The chain is certified by the Green Restaurant Association, and has completed 8 of the association's environmental steps: recycling and composting cardboard, glass, metal, and plastic, offering sustainable meat options, preventing pollution by not using polystyrene foam, using biodegradable cups, and outfitting its employees in organic cotton uniforms.

Because of their labeling, the corn cups are the restaurant's most obvious green effort, but are they too good to be true?

Most plastic is made from petroleum, but Boloco's cups are made from polylactic acid, or PLA. (This is done by a company called NatureWorks, a joint venture between Teijin Limited of Japan and the oft-vilified Cargill. Kudos to them for exploring environmentally low-impact technologies.) Lactic acid is made from dextrose by fermentation. Dextrose is made from starch, which in the case of these cups comes from corn. In places where corn is less common, the starch could come from crops including rice, sugar beets, sugarcane, wheat, or sweet potatoes.

All of these starch sources are also human food sources, and using them to create plastics instead of as a way to fill hungry bellies presents a problem. But in the U.S., we have more corn than we know what to do with, making the technique harder to argue with. And unlike petroleum, corn and other starchy crops are renewable resources, so making PLA uses far less fossil fuels than making regular plastic. You can see some comparisons of regular (PET) plastic and PLA plastic (marketed under the name IngeoTM) here.

But is PLA really 100% compostable? Probably not in your backyard compost bin, but in the closely regulated conditions of an industrial composter, it does compost within 45 days. And if your cup winds up in a landfill instead of a composter, it still biodegrades better than regular plastic, reacting like other food waste. Perhaps best of all, PLA products can be recycled and turned into more PLA products, which cost roughly the same amount as their plastic equivalents and work just as well.

What can you do to encourage the use of "corn cups" over traditional petroleum plastics? Patronize stores like Boloco that already use them, and be sure to say thanks for the cup. Ask what the cups are made of at other fast food restaurants, and tell the manager that you prefer to spend your money at places that use biodegradable ones.

Of course, if you really want to make a difference, the best thing you can do is bring your own re-usable cup.

1 commentaire:

Tim Dunn a dit…

There are a lot of problems with PLA - If we made all of the plastic disposable items used in the world every year out of PLA, it would take one hundred million tons of corn to make it. That would lead to mass starvation in the third world, as that represents at least 10% of the world's grain supply. It also takes a huge amount of diesel to grow, fertilize, ship, and process this corn, and as a practical matter, it is also not recyclable-In fact, the recyclers are trying to get PLA banned because it gets mistaken for PET, and ruins their PET batches. Restaurant owners and merchants find it annoying that PLA becomes gummy in water, gives water stored in it an odd taste, softens at soup temperatures, and has a short shelf life. And no, PLA can't be composted at home-it takes the elevated temperatures of a commercial composter to compost PLA. The alternative? Recyclable biodegradable plastics-Plastics made out of an otherwise useless industrial byproduct, naphtha. See for full information. -Tim Dunn