While biodegradable plastics are generally considered to be more eco-friendly than traditional plastics, a 2010 study from the University of Pittsburgh found that wasn’t necessarily true when the materials’ life cycles were taken into consideration.
The study compared seven traditional plastics, four biodegradable plastics and one made from both fossil fuel and renewable sources. The researchers determined that bioplastics production resulted in greater amounts of pollutants, due to the fertilizers and pesticides used in growing the crops and the chemical processing needed to turn organic material into plastic.
The biodegradable plastics also contributed more to ozone depletion than the traditional plastics, and required extensive land use.
While the biodegradability of bioplastics is an advantage, most need high temperature industrial composting facilities to break down and very few cities have the infrastructure needed to deal with them. As a result, bioplastics often end up in landfills where, deprived of oxygen, they may release methane, a greenhouse gas 23 times more potent than carbon dioxide.
When biodegradable plastics are not discarded properly, they can contaminate batches of recycled plastic and harm recycling infrastructure. If bioplastic contaminates recycled PET (polyethylene terephthalate, the most common plastic, used for water and soda bottles), for example, the entire lot could be rejected and end up in a landfill. So separate recycling streams are necessary to be able to properly discard bioplastics.
The land required for biodegradable plastics competes with food production because the crops that produce bioplastics can also be used to feed people.
