Corn-Based Plastics

July 4, 2008 at 2:39 pm Leave a comment

PLA = polylactic acid, is made from fermented plant (mostly corn) starch and considered a better alternative than the traditional petroleum-based plastic, polyethylene terephthalate (PET), used to make bottles. To make PLA, dextrose is extracted from corn starch, and them lactic acid is produced as a by-product in a fermentation process. Lactic acid is converted to lactide. The molecules then link together to form polymers that are polylactic acid. Therefore, PLA comes from a renewable carbon source, it reduces greenhouse gas emissions, and it does not release toxic gas when incinerated. The idea has been around for decades, but thanks to the technology that can now produce 1 pound of PLA for less than $1, more retailers are looking into PLA as their packaging option.

Don’t get too excited just yet. Although some manufacturers advertise its compostability, you can’t just throw the PLA containers into the compost pile in the backyard and expect it to biodegrade. It still takes a long time (estimated to be between 100 to 1,000 years, similar to PET) to degrade in compost piles and landfills, where the conditions are not optimal. It does not mix with common plastics, so it is considered a contaminant. Recycling facilities will need to separate PLA products from PET and dispose of them separately. Specific composting infrastructure is required to collect PLA, break them down, and reproduce them into usable products again. In the mean time, containers made of PLA will likely end up in landfills again. Its application is limited because it can not withstand high temperature (above 114ºF or 45.6ºC). Some opponents suggest that industry should develop replacement for other plastic products because plastic bottles already have an effective recycling system in play.

While the kinks need to be worked out, PLA is a potential solution to the “white pollution” while we continue the search for a perfect solution. If the government can administer a system in which everyone can separate all waste into recyclable, biodegradable, and others, which can be collected and processed accordingly, we can reduce the amount of garbage generated significantly (the Green Bin project in Toronto is a good start). However, the best way to help the environment is to avoid the use of plastics all together. Bring a canvas shopping bag when you go grocery shopping. Use reusable water bottles. Buy from merchants that use minimal packaging. Those are always better options while the scientists are trying to find a way to undo our mistakes.

Related links:
Scientific American – The Environmental Impact of Corn-Based Plastics
Biotech Route to Lactic Acid/Polylactic Acid
Smithsonian Magazine – Corn Plastic to the Rescue

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Entry filed under: General Science. Tags: , , .

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