Corn-based plastic has positive aspects such as requiring less energy to make than traditional plastic.  It also has its negatives, like taking a long time to disintegrate in landfills like regular plastic.  Do the positives outweigh the negatives?  Let’s see.

Corn-based (biopolymer) Plastic, better known as polylactide  or polylactic acid (PLA) plastic, is made from lactic acid using plant sugars.  Usually those plant sugars come from both GMO (genetically modified organism) corn and non-GMO corn.

NatureWorks, LLC is the largest PLA manufacturer in the United States and calls the PLA that they produce by the trade name ingeo.  The company is a joint venture between American company Cargill and Teijin Limited of Japan begun in 2007.

The company incorporates many green practices into its production of ingeo.  The company buys its feedstock (primarily corn) from local farmers, cutting down on greenhouse gases from long distance transportation.  Customers can choose a between GMO and non GMO feedstock for the manufacture of their PLA plastic.  Finally, NatureWorks uses Renewable Energy Credits (RECs) to purchase wind power.

Allowing alternate feedstock has become more important as opposition has grown to the agricultural practices of the large agribusinesses that raise corn most of which is GMO corn.  Agribusiness uses more fertilizers and pesticides for crops since it doesn’t use crop rotation to replenish the soil.  Although the feedstock for NatureWorks plastic is corn, even at full capacity the production of PLA uses less than one half of one percent of the available corn crop in the US.

NatureWorks has several different life cycle studies that show the cradle to grave environmental effects of producing PLA to be significantly less than the production of other plastics.  Part of that improvement comes from the companies use of renewable energy credits that it buys.  Specifically the company has increased the amount of Wind Energy credits that it purchases to off-set CO2 produced during the growth and manufacturing cycles of its plastic as well as looking for ways to improve the manufacture of PLA so that it is less water and energy intensive.

PLA plastic has a shorter life span than other plastics although it will still stick around for a long time in landfills and as litter.  This type of plastic can also be composted (industrial facilities only), incinerated, reduced to lactic acid again and recycled if properly sorted.

AzSustainability.com breaks the pros and cons down into two simple lists:

Pros:

• Manufactured from corn starch, a renewable resource.
• Biodegradable, breaks down into mostly carbon dioxide and water.
• Compostable, 6-12 months in a home composter (Many people are reporting that they will not compost in a home composter), 1-6 months in a commercial composter. Longer for heat resistant utensils. Once composted it is indistinguishable from the other compost.
• Does not emit toxic fumes if incinerated.
• Does not leech chemicals into food or soil.
• Freezer safe.
• Can handle hot items up to 120F (200F for utensils).
• Looks, feels, handles just like plastic.
• Is inexpensive.

Cons:

• Is not recyclable, must be kept separate from plastic. [NatureWork is working with recycling companies to develop better ways of sorting PLA so that it can be recycled]
• Few commercial composting facilities (113 in U.S.), only 1/4 of which accept residential materials.
• Commercial Composters use Microbes to break down organic material. Large amounts of PLA in a composter would cause problems because it breaks down into lactic acid which is wetter and more acidic. They can break this down but it requires more oxygen for the microbes to consume. Commercial Facilities would have trouble providing enough oxygen for large amounts of PLA to breakdown. Anaerobic digesters would not have the same problem.
• It is estimated that in a landfill PLA will take anywhere from 100 to a 1000 years to biodegrade.
• Typically made from genetically modified corn and usually not organic. [Can be made from non genetically modified corn]
• Diverting corn away from the world’s food supply.[According to NatureWorks this is a spurious complaint]

PLA manufacturing is still in its infancy compared to the manufacture of other plastics.  As such the process is expected to improve both the product and the efficiency of the process.

Finally, PLA does not contain chemicals like BPA so no chemicals can leech into food or drinks from PLA containers.

Do the pros outweigh the cons?  Considering that plastic has insinuated itself into just about every part of our lives from food packaging to clothing, using more environmentally friendly plastic is a vast improvement over the alternative.  Since PLA or biopolymer plastic can be manufactured into just about every plastic item known to humankind, that alone makes it a winner.

Tomorrow:  A look at various PLA products on the market and where to find them.

Photo by Majiscup

Related:

Entry was posted on Monday, June 15th, 2009 at 9:04 pm under Green Technology, Science and technology.

Read more entries by Susan Wilson.
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