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Is Corn Plastic Safe, Environmentally Friendly?

Michael Lehto  |  12/02/09 @ 4:00pm

I just received my new "Corn Plastic" mug from the recent WCPN fund drive and found myself wondering about this stuff. It's touted as being much greener than traditional plastic, and, of course, one can see the benefit of not having the massive inputs of petro-chemicals needed to make traditional plastic (this stuff is made purely from sugars derived from corn). It's supposed to be bio-degradable. But a quick search reveals that it needs 140 degrees consistently for 10 days, which most back-yard composting heaps can't sustain. Corn also takes a lot of petro-inputs to grow and harvest, and the increase in corn-based fuel has created tremendous controversy about the dramatic rise in food prices. So throwing yet another commodity into corn's court seems a little dubious. Are there any potential toxic additives to corn plastic that can leach out under the high heat of a microwave or boiling water? Anyone out there know much about this stuff?

Can you imagine life without plastic? Probably not – it’s everywhere. It’s cheap, it’s versatile and it’s durable. So durable that every piece of plastic we’ve ever produced on this planet is still here in some form another - whether it’s still being used for its original purpose, has been repurposed, is sitting in a landfill, floating in the middle of the Pacific, or littering beaches as sand and pebble sized particles, it’s still on the planet.

The vast majority, if not all, of the single use plastic we consume is virgin plastic. It’s a common misconception that plastic is recyclable in the sense that steel, aluminum, paper and glass are recyclable. Glass bottles are recycled and new glass bottles can be made. The same goes for aluminum, steel and paper – new aluminum, steel and paper products are made out of the recycled material. Unfortunately this isn’t necessarily the case with plastics. Recycling of plastics typically entails melting the plastic and reforming it, but the “new” plastic is often of lesser quality, or less pure, than the original.

Products made from recycled plastic are typically more durable than the original and usually are not recyclable. Examples include plastic lumber, parking lot car stops and speed bumps, textiles, etc. The American Chemical Council hosts a recycled plastics products directory that’s helpful in learning more about the potential uses for recycled plastic. Since most of these products are not recyclable, recycling plastic really only adds one extra stage of use, albeit it a durable one, before it ends up in a landfill where it will remain, for all practical purposes, forever…unable to degrade or breakdown.

So are bioplastics the sustainable answer to our “throw away” habits? They’re made from rapidly renewable resources - mostly food crops like corn, wheat, and sugarcane - and they’re biodegradable. Bioplastics seemingly fit the Cradle to Cradle bill – from the earth to the earth. But can it really be that simple? Are bioplastics the answer?

Let’s first address the fact that they’re made from rapidly renewable resources. Sounds sustainable; but is it really? Most bioplastics are made from cultivated crops and mass crop cultivation isn’t without its share of environmental nasties like petroleum-based fertilizers and chemical-laden pesticides and herbicides, not to mention accelerated soil erosion and extensive water use. Another issue with raising crops to replace petroleum is that it takes land away from actual food production. During the global food crisis last spring, crop-based biofuels were highly criticized for just that reason.

Okay, so the production of bioplastics is not without issues, but some will argue that it’s still better than the alternative. What about the fact that it's biodegradable and compostable?

While it’s true that most are compostable, the challenge lies in ensuring that they actually end up getting composted - and not just any compost heap will do. Your average backyard compost pile won’t produce sufficient heat to break down bioplastics in any reasonable amount of time. A bioplastic bottle you put in it today will still be there relatively unchanged a year from now.

Temperatures of 140 degrees Fahrenheit for 70-100 days are necessary for biodegradation to occur. In other words, bioplastics will not biodegrade in the natural environment – they need to be disposed of in a commercial or industrial compost facility. The Ohio EPA recommends that they be diverted to a facility that accepts food scraps since they’re so commonly used to make beverage bottles, cups, plates, etc. and are likely to be contaminated. These facilities are classified as Class I. There are 14 such facilities in Ohio, but five of them are non-commercial. Bioplastics that aren’t contaminated can be composted in facilities classified as Class I, II or III. These facilities have the ability to test for contaminants that could potentially reduce the quality of the compost.

In an effort to “go green” many business and organizations are beginning to switch to bioplastics. Unfortunately, few are providing separate disposal receptacles for these compostable items. In cases such as this these items end up either in a recycle bin where they will contaminate the recycle stream – bioplastics are not recyclable - or in a landfill where they are little better than traditional, petroleum-based plastics.

Landfills are anaerobic environments that significantly slow the breakdown of organic materials. Studies have found newspapers in landfills where the print, and the date, is still legible after 50 years. If a newspaper survives that long in a landfill, it’s likely that a bioplastic bottle, cup or fork will too. But all organic material will break down eventually. No one really knows how long it might take. It could take 100 years or a 1,000, but when it does one thing is certain, it will produce methane gas, a greenhouse gas 23 times more potent than carbon dioxide.

Obviously bioplastics are not without their own set of challenges or problems. Whether they’re better than petroleum-based plastics is hard to say. Only a true lifecycle analysis that takes into account all of the tradeoffs of each could help answer that question. The bottom line is that single-use items, although they may be convenient, simply aren’t sustainable. Bring your own bag, mug or fork.

So is there a future for bioplastics? Toyota thinks so. They’re already using plant based plastics in the third generation Prius and Toyota engineers have designed a carbon fiber concept car, the 1/X, made from seaweed.

This post originally appeared in 2008 and was answered by Laura Christie.

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