SVSU Creates solar oven to sanitize compost

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Here's a hot idea: SVSU creates solar oven to sanitize compost

by Jeff Kart
The Bay City Times
Thursday March 12, 2009, 2:42 PM



Ed Meisel bit into a piece of pizza and liked what he tasted.
The food was cooked in an oven that runs on the sun.

The oven, built by students at Saginaw Valley State University, is being used at the campus greenhouse to sterilize compost created by worms.
And, once in a while, to cook up some food for the people who work there.
"What a bright idea, huh?" said Meisel, a chemistry instructor and greenhouse director.

SVSU student Gretchen Roekle, 43, of Saginaw, helped build the oven for an independent study project.

The greenhouse takes in pre-consumer food waste from campus food operations - up to 150 pounds a day - as well as used coffee grounds from a Starbucks shop and shredded paper from SVSU offices.

Using red wiggler worms, the garbage is turned into compost and up to 50 gallons of "worm tea" a week in the summer, said student Jason Haubenstricker, 19, of Frankenmuth.

The compost and tea - or leachate from watering and worm excrement - needs to be sterilized before it's used for growing vegetables and flowers, to eliminate any potential harmful pathogens.

Meisel had been nuking the stuff in a microwave until Roekle came up with her solar cooker.

The oven, built of plywood and fiberglass insulation, is powered by a funnel-like array of reflective mylar that focuses sunlight into the top of the box through a window of double-paned glass.

The contraption is angled toward the sun with brackets and mounted on a cart with wheels, so it can be adjusted throughout the day.

Altogether, the oven cost about $300 to build. Roekle is working on a portable, low-cost unit that could be used at campgrounds, instead of propane and charcoal.

The solar oven isn't a new invention, Meisel said, but it was just what the greenhouse needed.

"One, it's simple," he said. "Two, it was low-cost, long-lasting and highly efficient. It's almost like a slow crockpot cooker."

Compost and tea that are sterilized in the oven are used to grow vegetables and flowers in another greenhouse located next door.

The lettuce, tomatoes and other vegetables are eaten by students in the campus cafeteria. Other plants are used for research studies. The compost and tea work like magic, Meisel says. "This time of year, we've got plants almost in full bloom," he said of the winter months.

Testing has shown that the greenhouse vegetables have up to 10 times the vitamins and folic acid of the ones you'll find at the supermarket, Meisel said. "This is like plants on steroids," he said.

The oven has been in use since August. "It functions well in the spring, summer and fall, Roekle said. "You just need light, not heat."

The oven works best when it's wheeled outside.
In the summer, the top temperature was about 400 degrees Fahrenheit, Roekle said. Anything above 250 is enough to sterilize the compost and tea, she said.

This winter, the oven is being used to help heat the greenhouse. "We had it up to 120 about a week ago," with sub-zero temperatures outside, Roekle said in late February. "It's amazing how powerful the sun is."
 

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