Scientists have been able to harness energy from bacteria for several years. Now, some scientists have developed a more efficient system, using bacteria that feed on sugar. The Great Lakes Radio Consortium’s Rebecca Williams has more:
Transcript
Scientists have been able to harness energy from bacteria for several years. Now, some scientists
have developed a more efficient system, using bacteria that feed on sugar. The Great Lakes
Radio Consortium’s Rebecca Williams has more:
It’s called a microbial fuel cell, and it works like this: the bacteria in the fuel cell feed on sugar in
food or lawn waste. In the process, they transfer electrons to an electrode, starting a flow of
electricity.
This new fuel cell is more efficient than older models, bringing the technology one step closer to
everyday use.
Derek Lovley designed the fuel cell. His research is published in the journal Nature
Biotechnology. He says because the U.S. consumes so much energy, he doesn’t think his fuel
cells will be used on a large scale here. But he says, in the future, consumers might be able to use
them in their backyards.
“Say you had an electric lawnmower and you clipped your grass clippings and threw them into
this type of system, and used it to charge up the battery to run your lawnmower the next
weekend.”
Lovley says it’ll be a while before anyone can buy a microbial fuel cell. Right now, the fuel cell
produces just enough energy to power a calculator.
For the Great Lakes Radio Consortium, I’m Rebecca Williams.
A pile of food waste awaits processing at a Duluth, Minnesota composting site. A wide variety of materials arrive each day - anything from unused frozen dinners to sheet rock to bird droppings from a nearby zoo. Photo by Stephanie Hemphill.
Lots of people have a compost pile in the backyard. They throw their grass clippings and kitchen scraps in a pile and let it sit. Eventually it turns into rich black stuff that can be spread on the garden. Many cities around the Great Lakes collect residents’ yard waste and turn it into compost on a bigger scale. In Duluth, Minnesota, they’ve taken it a step further. An industrial-sized compost operation uses some surprising ingredients. The Great Lakes Radio Consortium’s Stephanie Hemphill reports:
Transcript
Lots of people have a compost pile in the back yard. They throw their grass clippings and
kitchen scraps in a pile and let it sit. Eventually it turns into rich black stuff that can be spread
on the garden. Many cities around the Great Lakes collect residents’ yard waste and turn it into
compost on a bigger scale. In Duluth Minnesota, they’ve taken it a step further. An industrial-
sized compost operation uses some surprising ingredients. The Great Lakes Radio Consortium’s
Stephanie Hemphill reports:
There’s a steady stream of cars and pickups as people drop off leaves and branches. They’re
piling up their yard waste at the compost site of the Western Lake Superior Sanitary District in
Duluth, Minnesota. The Sanitary District takes care of the trash for Duluth and nearby towns.
At the back, four rows of future compost are cooking in the sun. They’re about 6 feet tall and
half a block long. They were mixed by a master chef of compost, Charlie Hitchcock. He’s about
to cook up a new batch. Today’s mix starts with biodegradable bags of kitchen scraps from
several restaurants.
“It’s a small load today, but it’s food waste and there’s animal hair that’s thrown in from some of
the pet grooming places. A lot of protein and nitrogen in that, I guess.”
Hitchcock consults a laptop computer to create his recipe. He plugs in the weight of the food
waste. The computer program tells him the right proportions of wood chips and leaves to mix in.
It’s aiming for the ideal combination of carbon and nitrogen. Most loads are about half wood
chips.
“Because it aerates it pretty good. And then I just keep punching a number in on the leaves until
I get between a 25-to-1 to a 35-to-1 on a C-N-N ratio, carbon to nitrogen.”
(tractor starts)
The key ingredient that’s loaded in Hitchcock’s mixture is different every day. That’s because the
sanitary district is always trying to divert stuff that would normally go to the landfill. Lately
they’ve been going after some of the garbage itself, not just yard waste. And sometimes that
garbage comes from some exotic places.
(bird sounds from zoo)
Dave Homstad takes care of the birds at the Lake Superior Zoo. He’s giving the parrots some
fresh water.
(parrot chit-chat)
He slides out the bottom of the cage and whisks sawdust and bird droppings into a black plastic
bag.
“The composting stuff goes into a black bag, so that we can keep them separate. And then
anything that can be composted goes in here and then eventually into a dumpster for that
purpose.”
The dumpster gets filled with uneaten food, animal bedding, like straw and sawdust, and animal
dung. At the composting site, the dumpster-load from the zoo might be mixed with scraps from a
coffee shop. A commercial fishing operation brings fish guts. Even sheetrock is ground up to
become compost. The latest addition is waste grain from the elevators on Duluth’s lakefront.
(train sound at elevator)
The Cargill elevator handles 50 million bushels of grain every year.
Roger Juhl manages the operation. He says there’s some spillage when railroad cars have to be
changed from one type of grain to another.
“So we have to clean them out and dump them onto the tracks, and then pick them up and put
them in the dumpster. And that’s where they’ll go to this recycling center.”
Juhl says he’ll probably save some money. He’ll still have to pay the hauler to take the grain
away, but he won’t have to pay for dumping it in the landfill. What’s even better, Juhl says he’ll
be doing something good for the environment.
“Hopefully it’ll be useful for something.”
It’s put to use, all right, in Charlie Hitchcock’s compost mixer.
(compost sound back up)
The mixer’s been turning for 15 or 20 minutes. Hitchcock peers into the barrel. The ingredients
look like chunky dirt, and smell like day-old garbage. He reaches in for a handful.
“I do the squeeze test on it. If you get it packed tight without moisture coming from it, it’s within
the 50% range, which is good.”
Hitchcock is learning how to turn an amazing variety of stuff into compost. Some days he gets a
load of spoiled vegetables from a grocery store. Other times it’ll be outdated frozen dinners.
“When I get a lot of wet pasta, I use some sheetrock and mostly grindings. That’s shredded up
tree branches and limbs that we have. I don’t put leaves in it because the pasta’s so wet, it gets
real gumbo-y.”
After six months in a pile, the compost is ready for customers, like Suzanna Didier.
“I mean, I’m glad they’ve figured out a way for us to decrease the amount of garbage that goes
into the stream, into the waste stream, because obviously that needs to be slowed down a bit. So,
it’s great.”
It’s an expensive operation that doesn’t pay for itself. Officials hope to recoup half their costs by
selling compost. As they get more raw materials, it’ll become more cost effective. Someday,
they hope everyone in Duluth will send their kitchen waste for composting.
For the Great Lakes Radio Consortium, I’m Stephanie Hemphill.
