Our Discovery Channel sister site How Stuff Works has put out an interesting video on how corn plastics work. The video is informative about how corn plastics, or PLA, is produced. But it got us thinking about other issues with PLA that weren't really addressed.Corn plastics are controversial for a few reasons, not the least of which are that they use a resource that is energy intensive to produce, and because they can really gum up the works of recycling centers when not sorted properly. PLA can be sorted and recycled, but it takes some energy intensive processes to do it. That means they're energy intensive, and carbon intensive, from the start all the way to the end.
Also, PLA looks a whole lot like other plastics such as PET. That means some PLA products can end up in the same recycling stream, contaminating it and rendering the new plastics unusable and a big waste of effort and energy.
Many manufacturers and organizations call for PLA products to be very clearly marked when used, so that they can be more easily sorted. However, that then calls for additional manufacturing steps such as printing.
All-in-all, PLA can be a more eco-friendly option in some ways, but isn't an ideal solution to petroleum-based plastics. And, because it takes corn to make it, it'll never be able to replace petroleum plastics anyway.