February 15, 2007
One of the hottest developments in greening our product systems is the growing interest in plastics made from organic matter rather than petroleum. Bioplastic technology for has been around for decades, but the low cost of oil has kept it out of the spotlight until recently. While the bioplastics revolution is well underway in Europe and Japan (France and Italy have banned non-biodegradeable plastic bags), it’s still gaining steam here in the States. Here’s a summary from a talk I gave for my Ecosa program:
Most bioplastics are made from starch – usually corn but also potato, soy and cellulose. Starch plastics are soft, easy to produce and decompose quickly, making them ideal for disposable products like trash bags, utensils and cups. Just don’t use them for coffee: unless they’re combined with other compounds, most starch plastics melt at 120 degrees.
While corn and potato plastic are by far the most common, there’s also quite a bit of plastic being developed for more demanding applications. Polyactide acid (PLA), made by fermenting sugars and starches, is starting to see use in everything from soda bottles to cell phones, while the bacterial compound Poly-3-Hydoxybutarate (PHB) is being used to make strong plastics that withstand temperatures up to 350 degrees F.
Like anything claiming to be “sustainable” these days, bioplastics come in a few shades of green. Plastics labeled as degradeable undergo a chemical transformation under specific conditions (usually when combined with another chemical), and generally still leave a toxic residue. Biodegradeable plastic products will degrade naturally from microorganisms – although it might take years to do so, and even then there might be components like glues or coatings that never decompose. To ensure that the plastics you buy can be safely returned to the soil, look for products that are compostable. These products are certified by the Biodegradeable Products Institute to decompose at the same rate as paper (less than 18 months) and leave no toxic material.
The idea of using old take-out forks to nourish the carrots in your backyard is pretty irresistable. But before we all jump on the bioplastics bandwagon, it should be noted that even compostable plastics come with a few caveats. While bioplastics themselves may be renewable, they still require a complicated, energy-intensive process to produce – energy that probably isn’t coming from wind farms or solar panels. There’s also the GMO issue: more and more bioplastics are being made from plants that are genetically modified to increase naturally-occuring plastic compounds, a seriously un-green prospect to many. Finally, the lack of composting infrastructure in most of the USA makes the environmental benefits of bioplastic largely irrelevant. Unless care is taken to dispose of bioplastic in a home or commercial compost facility, it could end up in a landfill, where the lack of oxygen will prevent it from breaking down for centuries.