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In what new ways can bacteria help shrink our landfills?


Plastic Eaters
Trash that might not degrade for millennia piles high in Kaua'i County, Hawaii.
Trash that might not degrade for millennia piles high in Kaua'i County, Hawaii.
Photo courtesy of County of Kaua'i

While plastic isn't really around forever, it might as well be. It typically takes thousands of years for the stuff to decompose under normal landfill conditions, which means every piece of plastic ever thrown away is still around in its original state, more or less.

Of course, some of the used plastic -- say, a water bottle -- is still around in the form of new plastic -- perhaps an eco-friendly lawn chair. Recycling means less "virgin plastic," which is a huge plus. Unfortunately, only a small percentage of water bottles are recycled. That's partly because people are throwing them in the wrong bin. But it's also because recycling plastic is difficult, energy intensive and not terribly profitable, so there's not a big capitalist push to get all those bottles into the right bin.

If recycling plastic were easier and more profitable, landfills would be growing at a slower rate. One of the more recent innovations in bacterial trash management helps us get there, with an additional perk: recycled plastic that's biodegradable.

The typical result of recycling PET plastic (the millennial degrader) is PET plastic. The upside is that it's not new plastic. But it's still going to be around for thousands of years. A new bacteria-based recycling process converts PET plastic into PHA plastic, which is both biodegradable and more economically valuable than PET.

Researchers at University College in Dublin, Ireland, discovered that a strain of bacteria called Pseudomonas produce PHA when they feed on components of PET. Basically, when PET plastic is heated anaerobically, it breaks down into three things: terephthalic acid (TA), oil and gas. When a Pseudomonas bacterium digests the terephthalic acid, it fills up with PHA plastic.

PHA is used in various medical supplies, mostly. It's expensive stuff, which means it can make recyclers a lot more money as an end result of the process. And even if some of that end result does end up in landfills, it'll degrade a lot faster than the original PET input.

Another new bacterial process produces nothing of real substance -- at least nothing that would collect in a landfill. A 16-year-old in Canada discovered a combination of bacteria that breaks down plastic bags into water and a bit of CO2.

An annual 500 billion plastic bags around the globe, each one taking millennia to breaks down, is significant landfill filler [source: Kawawada]. Daniel Burd's science fair project successfully isolated the bacteria that eventually break those bags down: Pseudomonas and Sphingomonas. Working in concert, with some sodium acetate added to the process, the bacteria digest down plastic in practically no time, a matter of months, not millennia.

Neither new approach is ready for commercial application. They're potentially scalable for broad use, but that'll take years of development. Another angle on bacterial trash management might be farther along, at least according to its proponents.


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