Why Compostable Plastic is Better for the Environment
The new compostable chip bags introduced by SunChips have two significant environmental advantages over conventional oil-based plastic. First, rather than being made from petroleum, a non-renewable resource, the plastic used to make the compostable chip bags is derived from plant material, a renewable resource. Second, the compostable plastic breaks down when tossed into a compost bin or pile, as opposed to most conventional oil-based plastics that do not decompose, often creating waste as litter or piling up in landfills.
According to the website of NatureWorks LLC, the company that manufactures the new compostable plastic, its production is greenhouse-gas-neutral, and uses 65% less fossil fuels than the manufacture of oil-based plastic such as PET (polyethylene terephthalate.)
How Compostable Plastic is Made
The new type of compostable plastic is called polylactic acid or polylactide. Produced by NatureWorks LLC under the name of IngeoTM, polylactide is a bioplastic film derived from corn. No genetically modified plant material is necessary for its production, and the amount of field corn used in the manufacture of Ingeo constitutes less than 1/20 of one percent of the world's yearly corn crop, which does not have a negative impact on the price or supply of food crops. For each pound of Ingeo produced, 2.2 pounds of corn are used.
The manufacturing process involves cooking the corn, grinding it to isolate the starch, and converting the starch to sugar. The material is then fermented by microorganisms, which convert the sugar into lactic acid. The lactic acid molecules are linked together into long chains to create the polylactide polymer. The polymer, called NatureWorks PLA, is formed into pellets that are used for a variety of products.
At present, Ingeo is made from corn, but any source of sugar can serve as raw material, including wheat, sugar beets or sugar cane. The company's website states that in the future, Ingeo will be producing non-food crops.
How Compostable Plastic Decomposes
The bioplastic film used in the new compostable chip bags break down into water, carbon dioxide and biomass when placed in an active compost bin or pile. Composting is a biological process in which organic material is digested by microorganisms such as bacteria and fungi. The resulting compost is a rich, dark organic material also known as humus, which can be used to promote the healthy growth of plants in gardens. The living organisms in a compost pile generate heat, and the heat speeds up the composting process.
Tests carried out in a hot, active compost bin that reached temperatures of 55 degrees C (131 degrees F) during the first two weeks showed that the bioplastic film of the SunChips bags will break down within 12 to 14 weeks, the same rate that it took for other organic matter to decompose. At lower temperatures or less than ideal composting conditions, it will take longer to break down.
The new compostable chip bags can reduce the use of non-renewable resources, as well as decrease waste, thus helping us to make strides toward a cleaner environment.
Current Status of Compostable Chip Bags
Consumer response to the new compostable chip bags was positive in terms of their environmental impact, but there were concerns that the material was very noisy. To address this issue, SunChips has reverted to conventional packaging for most of their products, and the compostable chip bags are currently only being used for specially-marked 10.5 ounce bags of their original flavor SunChips. They are working on a new generation of compostable plastic to address consumer concerns.