THEGREENGROK

When Greenware Breaks Down … on Its Eco-Friendly Promises


by Bill Chameides | June 6th, 2011
posted by Erica Rowell (Editor)

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So now that some plastics on the market are biodegradable, are they all good for the environment? Unfortunately, not in all respects. But there are fixes that could make them live up to their green rep.

Could products made of biodegradable material be bad for the environment?

Too Much Garbage

Of all the solid waste Americans produce every year, we send more than 50 percent of it (or 130 million metric tons plus) into landfills. That’s a whole lot of trash all on its own, but it also, as it turns out, happens to be contributing to lots of greenhouse gas emissions.

As landfill garbage breaks down, it produces methane, a greenhouse gas that’s about 25 times more effective than carbon dioxide as a global warmer. Even though roughly 70 percent of U.S. landfills are outfitted with systems to capture the methane (and roughly 35 percent use it to produce energy), it’s estimated that landfills are the third largest source of anthropogenic methane emissions in the United States, accounting for 17 percent of the total.

And there’s more. A good portion of the garbage we send to landfills is plastic — more than 10 million metric tons went into landfills in 2008 [pdf]. This plastic is a problem for two reasons:

  1. It breaks down very slowly. In general, stuff in landfills is broken down by microbes; they eat the garbage and convert it into energy and waste products. But plastics are made up of long-chained, tightly bound molecules that microbes find extremely difficult to “chew on” and so plastic waste can persist for years, adding to the volume of landfills long-term.
  2. Because plastic is generated from petroleum, all that plastic waste adds to landfills’ carbon footprint.

What’s to Be Done?

Clearly, one approach is adopting the three green R’s: reduce, reuse, recycle. That’s cool, but it doesn’t appear to be enough. For example, after many years of promotions aimed at the practice, the rate of plastic-bottle recycling has remained relatively constant at about 27 percent. (In 2009, the most recent year with data, we recycled a whole one percent more [pdf].) And where does the rest go? Mostly into landfills.

If you can’t change folks’ behavior, why not change the products they use? Rather than asking people to recycle, give them a plastic substitute: a plant-based, biodegradable polymer. These are polymers made up of smaller, less tightly bound molecules that microbes find easy pickings, and so unlike plastics, they break down quickly.

One such polymer known as polylactic acid or PLA is already making significant inroads in disposable eating accouterments such as cups, spoons, forks, and knives — but not without some bumps along the way. Do plant-based cups and utensils make a difference? In 2008, we landfilled almost 800,000 metric tons of just plastic plates and cups [pdf]. Because PLA is produced from plants instead of petroleum, its carbon footprint should be much smaller than plastic. And because it breaks down quickly, it has a smaller landfill footprint over time. Or at least that’s the theory

Problem Solved With the Plant-Based Plastic?

Not so fast, says James Levis and Morton Barlaz of North Carolina State University. They report in a paper published in Environmental Science & Technology that once these biodegradable materials end up as solid waste in a landfill, their very biodegradability means that they release methane very quickly. The authors estimate that, all things being equal, in the average U.S. landfill, PLA-based polymers have a rather large end-of-life greenhouse gas footprint — larger than other biodegradable wastes, and much larger than solid waste in general.

Oops?

So is that it it with plant-based plastic substitutes? Should we remove the green label on biodegradable products? That’s apparently one idea being floated in the blogosphere. (See LiveScience.com, Moonbattery.com and Wattsupwiththat.com.)

But it ain’t necessarily so. Levis and Barlaz offer up solutions — in the form of technological fixes to the chemical almost-fix:

  1. Produce a biodegradable product that biodegrades more slowly; and/or
  2. Practice state-of-the-art garbageology. (This is the one I like.) While biodegradable products are greenhouse-gas losers when using standard landfill technologies, the authors found that the tables were turned in an advanced, state-of-the-art landfill. There, PLA-based biodegradable products had a smaller greenhouse-gas footprint than standard garbage.

And there’s a good reason to opt for advanced landfills, beyond keeping biodegradable products green. Because much of the methane emitted from a state-of-the-art landfill would be captured and used for energy, such recycling would displace energy produced from fossil fuels, both saving money and giving these landfills a negative carbon footprint.

OK, but what’s to be done while you wait for your municipality to go “state of the art” on garbage? Well, don’t forget those tried-and-true three R’s. And when it comes to eating accouterments? The next time you find yourself going to an outdoor picnic, a potluck, or your favorite take-out joint, be sure to take along a set of real flatware, and dishes where applicable, from home. That’s what my mom’s generation would’ve done before the whole green thing got going.

filed under: climate change, faculty, global warming, methane, plants, pollution, waste
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