NCPA - National Center for Policy Analysis


May 3, 2010

Bioplastics could be really good for the environment -- the manufacturing process produces fewer greenhouse gas emissions than that for petroleum-based plastics, and these biomaterials don't contain an allegedly hormone-disrupting chemical, bisphenol A (BPA), that some regular plastics do.  But is society green enough to use bioplastics, asks Time?  Many of us still don't recycle all our bottles and cans, and now companies are expecting us to start composting? 

Bioplastics have been around for decades and interest in these materials has tended to fluctuate with the price of oil: 

  • Of the two promising new varieties of bioplastic, one type -- dubbed polylactic acid, or PLA -- is clear in color and costs manufacturers about 20 percent more to use than petroleum-based plastic.
  • The other -- called polyhydroxyalkanoate, or PHA -- biodegrades more easily but is more than double the price of regular plastic.  

Both bioplastics are made of fermented corn sugar, and both come with a major benefit -- if disposed of properly, they will not stick around in landfills for thousands of years.  However, that is a big if, says Time: 

  • The PLA resins that biodegrade when composted are showing up in more and more consumer products.
  • For example, NatureWorks makes polymers that are now in SunChips bags, water bottles in some government cafeterias and new Coca-Cola fountain soda cups.
  • PHA is more expensive, but it can handle higher temperatures and is the only bioplastic that will decompose in soil or waterways.
  • But, if a biodegradable fork ends up in an airtight landfill, it will most likely remain intact, just like regular plastic; however, should moisture seep in, bioplastics could anaerobically degrade and give off methane, a powerful greenhouse gas.  

According to Tillman Gerngross, an engineering professor at Dartmouth College, "When you dispose of biodegradable plastic, it decomposes into an air pollution problem." 

Discarded bioplastic is not the only potential methane emitter in landfills.  Kitchen scraps and yard waste emit the gas, which is one reason many garbage dumps have started capturing methane output and using it for energy, says Time. 

Source: Kristina Dell, "The Promise and Pitfalls of Bioplastic," Time, May 3, 2010. 

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