Environmental Benefits of Biodegradable Plastics Depend Upon Proper Disposal
There is much debate about the total carbon, fossil fuel and water usage in manufacturing bioplastics from natural materials and whether they are a negative impact to human food supply. It takes 2.65kg of corn to make 1kg of polylactic acid, the most common commercially compostable plastic. Since 270 million tonnes of plastic are made every year, replacing conventional plastic with corn-derived polylactic acid would remove 715 million tonnes from the world's food supply, at a time when global warming is reducing tropical farm productivity.
Traditional plastics made from non-renewable fossil fuels lock up much of the carbon in the plastic as opposed to being utilized in the processing of the plastic. The carbon is permanently trapped inside the plastic lattice, and is rarely recycled, if you neglect to include the diesel, pesticides, and fertilizers used to grow the food turned into plastic.
There is concern that another greenhouse gas, methane, might be released when any biodegradable material, including truly biodegradable plastics, degrades in an anaerobic (landfill) environment. Methane production from 594 managed landfill environments is captured and used for energy, some landfills burn this off called flaring to reduce the release of methane in the environment. In the US, most landfilled materials today go into landfills where they capture the methane biogas for use in clean, inexpensive energy. Of course, incinerating non-biodegradable plastics will release carbon dioxide as well. Disposing of biodegradable plastics made from natural materials in anaerobic (landfill) environments will result in the plastic lasting for hundreds of years.
Bacteria have developed the ability to degrade plastics. This has already happened with nylon: two types of nylon eating bacteria, Flavobacteria and Pseudomonas, were found in 1975 to possess enzymes (nylonase) capable of breaking down nylon. While not a solution to the disposal problem, it is likely that bacteria have developed the ability to consume hydrocarbons. In 2008, a 16-year-old boy reportedly isolated two plastic-consuming bacteria.
Read more about this topic: Biodegradable Plastics
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