Pros and Cons of PLA: Corn-Based Plastic

Plastic baby bottles and dishes, close-up
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Polylactic acid (PLA), a plastic substitute made from fermented plant starch (usually corn) is quickly becoming a popular alternative to traditional petroleum-based plastics. As more and more countries and states follow the lead of China, Ireland, South Africa, Uganda and San Francisco in banning plastic grocery bags responsible for so much so-called “white pollution” around the world, PLA is poised to play a big role as a viable, biodegradable replacement.

Proponents also tout the use of PLA — which is technically “carbon neutral” in that it comes from renewable, carbon-absorbing plants — as yet another way to reduce our emissions of greenhouse gases in a quickly warming world. PLA also will not emit toxic fumes when incinerated.

However, there are still issues with the use of polylactic acid such as its slow rate of biodegradability, its inability to mix with other plastics in recycling, and its high use of genetically modified corn (though arguably the latter could be one of the good effects of PLA as it provides a good reason to alter crop yields with genetic splicing).

The Cons of PLA: Biodegradation Rate and Recycling

Critics say that PLA is far from a panacea for dealing with the world’s plastic waste problem. For one thing, although PLA does biodegrade, it does so very slowly. According to Elizabeth Royte, writing in Smithsonian, PLA may well break down into its constituent parts (carbon dioxide and water) within three months in a “controlled composting environment,” that is, an industrial composting facility heated to 140 degrees Fahrenheit and fed a steady diet of digestive microbes.

But it will take far longer in a compost bin, or in a landfill packed so tightly that no light and little oxygen are available to assist in the process. Indeed, analysts estimate that a PLA bottle could take anywhere from 100 to 1,000 years to decompose in a landfill.

Another issue with PLA is that it must be kept separate when recycled, lest it contaminates the recycling stream; since PLA is plant-based, it needs to be disposed of in composting facilities, which points to another problem: There are currently a few hundred industrial-grade composting facilities across the United States.

Finally, PLA is typically made of genetically modified corn, at least in the United States. The largest producer of PLA in the world is NatureWorks, a subsidiary of Cargill, which is the world’s largest provider of genetically modified corn seed. This is tricky because the future costs of genetic modification (and the associated pesticides) to the environment and human health are still largely unknown.

Pros of PLA Over Plastics: Utility and Biodegradability

Genetically modified foods may be a controversial issue, but when it comes to genetically spicing plants together to breed corn that yields more crops for industrial use has its major advantages. With increasing demand for corn to make ethanol fuel, let alone PLA, it’s no wonder that Cargill and others have been tampering with genes to produce higher yields. At least harmful plastic isn't be used as frequently anymore!

Many industries are using PLA because they are capable of biodegrading at a much faster rate than plastic while still offering the same level of sanitation and utility. Everything from plastic clamshells for food take-out to medical products can now be made from PLA, which drastically reduces the carbon footprint of these industries.

While PLA has promise as an alternative to conventional plastic once the means of disposal are worked out, consumers might be better served by simply switching to reusable containers — from cloth bags, baskets and backpacks for grocery shopping (most chains now sell canvas bags for less than a dollar apiece) to safe, reusable (non-plastic) bottles for beverages.