Biodegradable Plastics Questioned

Biodegradable plastics may not help the environment
Biodegradable plastics may not help the environment.

Can we have it both ways: use plastic and save the environment at the same time? Biodegradable plastics, the kind that is supposed to break down in landfills and not languish forever as pollutants of land and sea,  have been touted as the plastic you can use with a clear conscience.

But can you? A recent analysis reveals that biodegradable plastics probably do more harm than good for the environment and climate change.

James Levis and Morton Barlaz at North Carolina State University (NC State) carried out a lifecycle analysis of biodegradable polymers. Microorganisms work away at the biodegradable polymers in plastics and help the process of degradation.

Methane is supposed to be one of the products from the breakdown of biodegradable plastics. Methane is a gas, which, if not captured and used as a energy source, goes into the atmosphere and becomes a greenhouse gas. It contributes to climate change.

In the report published in the journal, Environmental Science and Technology, the researchers found that the rate of breakdown of the biodegradable plastics by the microorganisms is faster than was previously thought. Public communication specialist Matt Shipman of NC State News Services explains:

This problem may be exacerbated by the rate at which these man-made biodegradable materials break down. Federal Trade Commission (FTC) guidelines call for products marked as ‘biodegradable’ to decompose within ‘a reasonably short period of time’ after disposal. But such rapid degradation may actually be environmentally harmful, because federal regulations do not require landfills that collect methane to install gas collection systems for at least two years after the waste is buried. If materials break down and release methane quickly, much of that methane will likely be emitted before the collection technology is installed. This means less potential fuel for energy use, and more greenhouse gas emissions.

It could be that letting the biodegradable plastic sit around for longer in a landfill may be more environmentally friendly. The researchers think that with the slower degradation, most of the methane production will happen after the methane collection system is put in place. In other words, it may be best to do the opposite of what the FTC recommends.

You can listen to a podcast describing the work by Levis and Barlaz at the Scientific American‘s “60-Second Earth.” Environmental and energy journalist David Biello gives a quick and easy rundown of the analysis.

Source: “Are Biodegradeable Plastics Doing More Harm Than Good?,” Scientific American, 06/05/11
Source: “Is Biodegradability a Desirable Attribute for Discarded Solid Waste? Perspectives from a National Landfill Greenhouse Gas Inventory Model,” Environmental Science and Technology, 05/27/11
Source: Study: “Biodegradable Products May Be Bad For The Environment,” NC State Newsroom, 05/31/11
Image by mathiasbaert, used under its Creative Commons license.

Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.