What is corn-based plastic?

For a long time, the corncob pipe was considered a quirky accessory, associated with hillbillies, Frosty the Snowman, and Gen. Douglas MacArthur. While it still carries that rustic charm today, corn is now becoming a key ingredient in producing various everyday items — and it's no longer resembling something straight out of "Hee Haw." What appears to be ordinary, oil-based plastic is, in fact, polylactic acid (PLA) plastic, made from specially processed corn crops.

Yes, you heard it right: corn plastic. It's used in everything from coffee cups and grocery bags to clothing and even surfboards. The most significant advantage? It helps reduce our reliance on petroleum. Much like corn-based ethanol, corn plastic allows us to create a similar product using a renewable resource, unlike oil reserves that are finite. Plus, since corn can be grown worldwide, its value isn’t tied to relations with oil-rich countries or the stability of the Middle East. After all, have you ever seen "No blood for corn" on a T-shirt?

The United States consumes 20.8 million barrels of oil daily, with 10 percent dedicated to making traditional plastics like polyethylene terephthalate (PET) [sources: CIA World Factbook, Jewell]. Bioplastics such as corn plastic, on the other hand, don't require oil and have the added benefit of producing fewer toxins and greenhouse gases during manufacturing.

In addition, unlike conventional plastics that can linger in the environment for centuries after being discarded, corn plastic can break down in just a few months. Plus, if you choose to burn it, you won’t be releasing harmful fumes.

In this article, we'll explore how a corn stalk is transformed into a plastic trash can and discuss why some skeptics aren't fully convinced that bioplastics are the miracle solution they seem to be.

Manufacturing Corn Plastic: From Kernels to Coffee Mugs

If the idea of transforming a cornfield into biodegradable plastic products feels like something out of a sci-fi novel, you'll be intrigued to learn that bioplastics have a long history. The plastic celluloid, created in the late 1860s, was made from guncotton (acid-treated cotton) and camphor derived from the camphor laurel tree in Asia. While finding breakfast soy sausage in the 1930s would have been a challenge, automotive pioneer Henry Ford was already creating car parts from soybeans. In 1941, Ford introduced the 'Soybean Car,' which featured a bioplastic body atop a steel frame.

World War II interrupted Ford's efforts to merge agriculture and automobiles, but bioplastics weren't forgotten. The environmental movement of the 1980s sparked a revival in bioplastics, though they remained expensive to produce and couldn't quite match the performance of petroleum-based plastics. Still, with the unpredictability of the oil market, it was only a matter of time before a more affordable and durable bioplastic would be developed.

In the 1990s, U.S. commodity powerhouse Cargill Inc. deepened its research into the potential of bioplastics, and by 2000, partnered with Dow Chemical Company to produce polylactic acid (PLA) plastics made from corn. Cargill continued the venture with Japan's Teijin Ltd., resulting in corn plastic through NatureWorks LLC. As oil prices climbed and consumer demand for sustainable products grew, corn plastic became an increasingly viable business opportunity.

So, how is corn plastic made? First, the corn is harvested, soaked, and ground to separate the endosperm from the gluten and fiber, much like other grain crops. Next, enzymes are introduced to convert the starches in the endosperm into dextrose, a simple sugar. Bacterial cultures are then added to ferment the sugar into lactic acid, a process similar to beer brewing. This lactic acid consists of lactide molecules, which bond to form long polymer chains. The result? PLA plastic pellets, which can be spun into fibers or melted into virtually any shape.

Once you've removed the corn plastic packaging from a product or worn that corn plastic polo shirt out, the material only needs a month or two in a high-humidity composting environment at around 140°F (60°C) before it biodegrades and returns to the Earth, from which it originated [source: Herrick].

Despite its many advantages, corn plastic has faced criticism, even from environmentalists. In the next section, we'll dive into the pros and cons of sourcing your plastic from cornfields.

Bioplastics: The Benefits and Drawbacks

Bioplastics represent nearly 331,000 tons (300,000 metric tons) of the global plastics market [source: European Bioplastics]. While that may seem substantial, it still makes up less than 1 percent of the 200 million tons (181 million metric tons) of synthetic plastics produced each year [source: Green Council]. However, the bioplastics sector is expanding by 20 to 30 percent annually, though it's not without criticism [source: Vidal].

What could be wrong with utilizing a renewable resource grown in fields and composted once it's no longer needed? As it turns out, there are several drawbacks. For one, corn plastic only decomposes in the high-temperature, moist conditions of a commercial composting facility. If you simply discard a corn plastic item from your car or bury it in your backyard compost pile, it will last as long as standard PET plastics.

When commercial composting is unavailable, PLA plastics may end up in landfills or be mixed into regular plastic recycling streams. So, what’s the issue with placing corn plastics in the recycling bin? At first glance, they might appear similar to other plastics, but their chemical makeup is entirely different. Even small amounts of bioplastics can contaminate conventional plastic recycling, preventing it from being processed effectively and hindering recycling companies from profiting from valuable materials.

Because of these risks, companies like NatureWorks are proceeding cautiously by slowly introducing corn plastic products while working with commercial recyclers to detect contamination early. Bioplastics producers argue that the threat is exaggerated and that recycling is a more viable option for PLA plastics like corn plastic, especially considering they make up such a small percentage of the plastics market. Additionally, since PLA plastics emit the greenhouse gas methane when they break down, composting isn’t a flawless disposal solution. However, unlike petroleum-based plastics, bioplastics don't release toxic fumes when incinerated.

To avoid the complications associated with mixed plastics, commercial composters in the Northwestern U.S. only accept bioplastics from food service businesses, not individual households. This strategy means that bioplastics could be effectively utilized at events like sports games, where food is purchased and consumed on-site in large quantities.

Like corn ethanol, corn plastic has faced criticism for its reliance on industrial farming of vast crop fields that could otherwise be used to grow food for a growing global population. Much of the corn used for bioplastics is a variety called Number 2 Yellow Dent, primarily grown for animal feed. Additionally, some of this corn is genetically modified. However, NatureWorks assures that even if genetically modified corn is used for your plastic water bottle, the modified proteins are destroyed during the transformation into PLA plastic, meaning there’s no need to worry about consuming them [source: Jewell].

Supporters emphasize that the bioplastics industry is still in its early stages, with future plans to rely exclusively on agricultural waste (such as stalks and stems) for production. These long-term goals are also used to explain the higher costs associated with bioplastics research and production. PET plastics are a well-established commodity, with years of optimization behind them. Bioplastics proponents argue that over time, the cost of PLA will decrease, while the price of petroleum-based plastics will continue to fluctuate due to unstable production areas and diminishing resources.