A Plastic That is Good for the Earth?

The United States has been estimated to use more than 200,000 barrels of oil a day to produce plastic. It's light weight, low cost, and versatile uses have made plastic an integral, and seemingly indispensable part of our daily living. However, plastics take a heavy toll on our environment, from the use of fossil fuels, chemical leakages into our food and drink, to it's inability to biodegrade in a reasonable timespan. So, like most environmentally conscious people, I was excited when I heard about new plastics that were being produced from corn. Corn based plastics are billed as a biodegradable, sustainable alternative to petroleum based plastic. It can be disposed of in a number of ways: recycling, compost, incineration, and chemical conversion back into lactic acid through hydrolis. Clothing produced from this material is said to be hypo-allergenic, bacteria, odor, stain, and wrinkle resistant. Use of this material has grown quickly in the last few years, as manufactures struggle both to become more earth friendly and reduce their dependence on fossil fuels. Wal-Mart has announced plans to use 114 million PLA containers a year. Company executives estimate such a move will save the company 800,000 barrels of oil annually. But are corn based products really the answer to our plastic woes? Is it too good to be true?

Corn based plastics are manufactured from monomers made from the starchiest part of the corn kernel. Typically, the corn used to produce these monomers is field corn, which is primarily used for livestock feed. These monomers are then shipped to a polymer plant where they are turned into long strands of material that is eventually cut into tiny pellets. These pellets are then shipped either to the textile mill or plastics plant where the final product will be created. The "germ" leftover from this process is then processed into other components. For example a typical kernel of corn contains 16% water, 19% protein & fiber, 4% corn oil and 61% starch. Currently only 3 manufacturers in the United States produce corn plastics: Cargill (NatureWorks, PLA and Ingeo), Metabolix (Mirel), and Dupont (Dupont, Sorona). But interest is growing, as more and more plastics and textile producers seek a way to get involved in something that seems to be as good for the pocketbook as it is for the environment.

But just how "green" are corn plastics really ? NatureWorks claims that the production of their PLA uses up to 50% less petroleum than is used by conventional plastics resins (from field to checkout counter) AND contributes 40% less greenhouse gasses to the environment than traditional plastics - good numbers by any account, but what about corn plastic's other claims?

Corn plastic is recyclable, but must be separated from other types of plastics, lest it contaminate the recycling stream of those plastics. As most areas do not yet have sufficient resources to separate these newer plastics from their petroleum-based counterparts, corn plastic is not recyclable, in practice, in most of the country. NatureWorks, at least has given this problem some thought. Spokeswoman Bridget Charon states "If the MRF [materials recovery facility] separates the PLA, we will buy it back from they've got enough to fill a truck."

As for it's other claims for eco-responsibility, it is incineratable without releasing toxic fumes, it generally lasts just as long as it's petroleum-based competition, and it's compostable...sort of.

If you were thinking of taking your used corn-plastic refuse out back to your home composting bin, you're going to be mighty disappointed. While it is true it can be composted, few mention that this is only true if you are planning on sending your spent plastic to an industrial composting facility.With

fewer than 113 such facilities in existence across the nation including those that prison and college facilities and encompassing those that process yard waste, industrial food processing waste, and the handful (about 1/4) that accept residential food scraps collected by municipalities. Meaning that few will have access to the type of  Backyard composting is essentially impossible. For corn plastics to biodegrade, a temperature of 180 degrees and humidity of 95% must be maintained. Meaning there is no chance this material will biodegrade over an individuals lifetime if someone tosses it out their window or drops it in the street.

Some professional composters have their reservations even then. Chris Choate of Norcal Waste Systems fears that large amounts of PLA could interfere with conventional composting as the material decomposes back into lactic acid, effecting the moisture and acidity of the composting environment.

What about water use? While corn does require far more water to grow than crops such as wheat, alfalfa or potatoes , it does require less freshwater per kg of food produced than rice, soybeans, chicken, or beef (according to "The Worlds Water 2000-2001 the Biennial Report on Freshwater"). Emerson Nafziger, Professor of Crop Productin and Extension Agronomist at the University of Illinios, Urbana-Champaign says that "We should view every pound of dry matter in the crop as produced at the expense of about 50 lbs of water."

Overall, it looks as though corn-based plastic products are unlikely to fully live up to their "green" potential until adequate and appropriate waste disposal systems are in place. Which could take some time. In the meantime however, buying items made with corn plastic takes money away from petroleum-based products, saves fossil fuels, and supports an alternative industry that is at the very least more sustainable than the one we've relied on (and destroyed our planet with) for decades. There's something to be said for getting things moving in the right direction.