Audio Garbage reborn as compost (story audio) Photos Compost in Duluth comes from unusual raw materials. Homeowners bring brush and branches. A pile of food waste awaits processing. View full slideshow (11 images) Your Voice Join the conversation with other MPR listeners in the News Forum.

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Garbage reborn as compost
by Stephanie Hemphill, Minnesota Public Radio
May 5, 2003

The Western lake Superior Sanitary District collects waste from grain elevators, restaurants, the zoo, even pet groomers. It's all turned into compost. (MPR Photo/Stephanie Hemphill)

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. In Duluth, folks have moved beyond the back yard pile. They compost on an industrial scale, using some surprising ingredients.

Duluth, Minn. — The Western Lake Superior Sanitary District takes care of the trash and waste water for Duluth and other towns nearby.

At the district's composting site, there's a steady stream of cars and pickups. People dump bags of leaves onto a pile that begins to look like a small hill. They unload branches and brush onto another pile.

Toward 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 a few months ago by a master chef of compost, Charlie Hitchcock. He's about to cook up a new batch.

	A pile of food waste awaits processing.

Today's mix starts with biodegradable bags of scraps from several restaurants.

"It's a small load today," Hitchcock says. "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 in the small building next to the cement slab where he does his mixing. He plugs the weight of the food waste into his computer program. It tells him the right proportions of wood chips and leaves, to mix with the food waste. It's aiming for the ideal combination of carbon and nitrogen for making compost. Most loads are about half wood chips, which keeps the pile aerated.

"And then I just keep punching a number in on the leaves," Hitchcock explains, "until I get between a 25-to-1 and a 35-to-1 ratio, carbon to nitrogen."

	Loading the mixer.

Hitchcock has his recipe, and he's ready to combine the ingredients. The mixer is a bright red metal barrel on wheels. It's the size of a hot tub, only taller. It's attached to a full-size tractor, to power the auger that does the mixing.

Hitchcock uses a front-end loader to dump the food waste into the mixer. Then he adds a load of chipped wood and several loads of leaves.

The key ingredient in Hitchcock's recipe is different every day. That's because the sanitary district is always trying to reduce the amount of stuff headed for the landfill. Lately they've been going after garbage itself. And sometimes it comess from some exotic locations.

	Dave Homstad takes care of the birds at the zoo.

Dave Homstad takes care of the birds at the Lake Superior Zoo. He chats with the parrots and the lorikeet as he gives them fresh water.

He slides out the bottom of the lorikeet's cage and whisks sawdust and bird droppings into a dustpan.

"We use black bags and clear bags," Holmstad says. "Garbage in the clear bags and the composting stuff goes into a black bag, so we can keep them separate. Anything that can be composted goes in a black bag, 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. They don't put the primates' stuff in the dumpster, because they don't know if primates' diseases could be transmitted to humans.

Three times a week a truck comes to pick it all up. 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.

Charlie Hitchcock puts it all to good use.

	The "squeeze test."

After his mixer has been turning awhile, he climbs up a ladder to peer into the batch. It looks like chunky dirt, and smells like day-old garbage. He reaches in for a handful, and gives it a squeeze.

"Sometimes I'll mix it for 15 minutes, sometimes it'll go for a half an hour," he says. "Moisture content, 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 teaching himself 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," Hitchcock says. "That's shredded up tree branches and limbs. I don't put leaves in it because the pasta's so wet, it gets real gumbo-y."

In the summer, grass clippings provide a lot of nitrogen. At other times, Hitchcock has to add fertilizer.

His latest ingredient comes from the grain elevators on Duluth's waterfront.

	Waste grain helps make compost.

Cargill has just decided to send its waste grain for composting. The Cargill elevator handles 50 million bushels of grain every year.

Roger Juhl manages the operation. He says they might get ten or 15 dumpster-loads of waste in the course of a year. It can happen when a railroad car still has a little corn in it, but needs to be loaded with oats.

"So we have to clean them out and dump them on the tracks," Juhl says. "Then we 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. He doesn't mind saving a little money, but he's even happier to be doing something good for the environment.

"Hopefully it'll be useful for something," he says.

Lots of people think it's useful. Suzanna Didier came to the compost site to drop off a load of branches and leaves. She decided while she was there, she'd scoop up a couple of buckets of compost for her garden.

	Gardener Suzanna Didier.

"I'm glad they've figured out a way for us to decrease the amount of garbage that goes into the waste stream, because obviously that needs to be slowed down a bit," Didier says. "So, it's great!"

The compost is getting picked up so fast, it'll be gone by mid-summer.

Officials are trying to get more raw materials, especially garbage with a lot of nitrogen. They're hoping to get the waste from a fish hatchery, which would be full of droppings and uneaten fish food.

And someday they hope everyone in Duluth will send their kitchen waste for composting.

It's an expensive operation, and it'll probably never pay for itself. But it keeps stuff out of the landfill, and turns it into something useful.

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