Question from JG
What would you recommend for a green garbage bag? Could you try to demystify the different materials used in the biodegradable ones?
Judi – Vermont
Debra’s Answer
There are two kinds of “biodegradable plastic” bags.
One is made from polyolefin or polyethylene (a petrochemical plastic made from nonrenewable crude oil), which has been modified with an additive that accelerates the breakdown of the plastic into fragments of “organic carbon” that can be processed by microorganisms in an ecosystem. The problem with plastic is not that it doesn’t break down, but that it can take 1000 years to do so. The additive causes the modified plastic to degrade in predictable and controllable timeframes. Landfill trials for showed that one brand lost more than 95% of its molecular weight in less than 10 months.
The other type of plastic is a bioplastic made from renewable resources such as corn, potatoes or wheat. These generally degrade at least 90% within 180 days or less when composting conditions (including heat, moisture, and aeration) are present. Such bioplastics include Polycaprolactone (PCL), Polyvinyl alcohol (PVA) and Polylactic acid (PLA).
There are pros and cons to each.
The petrochemical plastic with additive is cheaper to produce and look, act and perform just like their non-degradable counterparts. But they are made using fossil fuels (which contribute to global warming through the release of carbon dioxide).
Bioplastics have poor strength–when used to store vegetables or filled with wet leaves and set out for trash pickup, they can begin to biodegrade and fall apart. So these are great for bringing produce home, but not for storage. They also may become defective from conditions during shipping and sitting on the shelf.
