D'Arcy Norman/FlickrResearch from North Carolina State University shows biodegradable plastics can release methane while decomposing.
Bad news about “environmentally friendly” biodegradable plastics: They may not be so environmentally friendly after all.
According to research from North Carolina State University, biodegradable plastics can release large amounts of methane while decomposing. And methane is a potent greenhouse gas.
The study was funded by Procter & Gamble, a major manufacturer of plastic products.
“Everybody assumes that biodegradable is desirable. This study calls that into question,” Morton Barlaz, one of the researchers who conducted the study, told the McClatchy-Tribune News Service.
Biodegradable plastics, or green plastics, are made from plant derivatives and take a just a few years to decompose.
Traditional plastics, made from petroleum byproducts, can take decades, centuries, even millennia to disappear.
Barlaz and his team say it’s this difference in rate of decomposition that is part of the issue.
Here’s why: Federal Trade Commission guidelines require that any product marked as compostable or biodegradable must decompose within “a reasonable short period of time” after disposal.
But other federal regulations don’t require landfills with gas collection systems to collect methane gas until two years after the waste is buried. That means a quick-decomposing plastic in a landfill is going to release all of its methane into the atmosphere before it can be collected.
Therefore, a slower rate of decomposition may be better for the environment.
“If we want to maximize the environmental benefit of biodegradable products in landfills,” Barlaz told ScienceDaily, a science news service, “we need to both expand methane collection at landfills and design these products to degrade more slowly.”
James Levis, the primary author of the study, is adamant that traditional plastics are not better than biodegradable plastics in terms of their environmental impact.
He says the take-home message is that landfills need to do a better job collecting gas from decomposing garbage.
“One would need to study the entire life cycle of the material to know if it was better or worse than the alternatives,” Levis said. “One should also look at other environmental factors … before making a final judgment.”
The research appeared in the journal Environmental Science & Technology.