Researcher Sets Record Straight on Biodegradable Plastics

Landfills that collect greenhouse gases are best for the environment
Landfills that collect greenhouse gases are best for the environment.

James Levis and Morton Barlaz at North Carolina State University (NCSU) had published a study a couple of months ago that analyzed the release of greenhouse gases by biodegradable plastics in landfills. Greenhouse gases contribute to climate change. Media outlets, including this blog, covered the research but with different, and often inaccurate, takes on it.

Levis has now written a piece in Plastics Today to set the record straight. He writes: “The headlines ranged from the measured (‘Study: Biodegradable plastics can release methane’) to the reckless (‘Biodegradable products are often worse for the planet’).”

Levis explains the work was an analysis of the greenhouse gas emissions associated with throwing waste into both national-average and state-of-the-art landfills. A state-of-the-art landfill collects the generated methane, a type of greenhouse gas, and turns it into something useful. About 35% of waste in the U.S. ends up in state-of-the-art landfills and about 31% of waste goes into landfills that don’t collect gas. The rest of the waste heads to landfills that collect and flare the gas.

Levis and Barlaz’s research showed that there are benefits to collecting landfill gas and turning it into something useful. Because state-of-the-art landfill capture methane, waste disposal at these landfills ended up being carbon negative. In other words, the landfills removed more carbon from the atmosphere than they release.

But disposing similar waste in an average landfill caused positive greenhouse gas emissions. The research also showed that the more degradable a material is, the more greenhouse gas it released when disposed in a landfill.

Levis and Morton concluded that the best material to have in a landfill, from a greenhouse gas emissions point of view, is one that didn’t degrade at all.

As Levis points out in his piece, reactions to the study are all over the map. For instance, the anti-environmentalists jumped on the data and tried to hijack them to say anthropogenic climate change doesn’t exist. As Levis says, “This research is meaningless if one does not first accept basic climate science. The purpose of the research is to allow us to more effectively mitigate GHG emissions by making informed decisions.”

Levis goes on to explain why other conclusions drawn by other groups are misguided. With biodegradable plastics, Levis says the study’s only mention of bio-based, non-biodegradable products was to show that they:

… would lead to the least greenhouse gas emissions in a landfill. We also showed that materials that degrade more slowly or to less of an extent lead to reduced [greenhouse gas] emissions in landfills.

Levis says the study does suggest that the best thing to do is to aggressively collect methane from landfills. He also reminds readers that a systemic approach must be taken when analyzing complex problems.

It’s worth noting, though, that perhaps some of the hysteria in the media over biodegradable plastics mentioned in Levis and Morton’s work can be traced to the press release sent out by NCSU’s Newsroom, where the eye-catching headline said: “Study: Biodegradable Products May Be Bad For The Environment“.

Source: “Collecting landfill gas good step,” Plastics Today, 07/08/11
Image by D’Arcy Norman, 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.