A Little Independent Energy Experiment on the Prairie

If you can fight your way through the dirt storms of Madelia, Minnesota, you may be able to find the future of renewable energy

Madelia, Minnesota is a small town with a big plan to produce fuel made from local materials for local markets. (Maggie Koerth-Baker)

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During our interview, Meschke spoke apathetically about the low civic involvement. It didn’t surprise her. It didn’t worry her. I got the impression that were she not the driving force behind the Madelia Model and thus inherently interested, Meschke might be skipping the meetings as well. For all of her mesmerizing confidence, she held no illusions about how the grassroots grows. Most people, she said, were just busy with their day-to-day lives. They’d get interested, but only when the Madelia Model finally gave them something tangible to be interested in. “Right now, what do we have to offer?” she said.

I could see her point. The farmers I knew seldom responded well to maybe/possibly/someday. Either you do something and give us the sales pitch when it’s ready to go, or you don’t do anything, and you shut up about it. (Yoda would have made a great farmer.) “We’ve got the choir signed on,” Meschke said. “And we’ve got a tentative congregation watching to see what happens next.”

This past fall, the Madelians finally got to see some action. Ironically, their first glimpse of the future looked an awful lot like the past. Researchers from the University of Minnesota drove a pickup truck from St. Paul to the farm country around Madelia. Behind it, on a trailer not much bigger than a small camper, they towed a system that could turn just about any kind of plant or animal material into fuel. The technology was new, but the concept behind it was more than a century old.

Beginning in the 19th century, threshing machines traveled from farm to farm during harvest time. A mechanical system for separating grain from its stalk was too expensive to pick out for yourself from the Sears catalog, so the thresher was a portable business. Maybe one guy owned and operated the machinery as his job, or several farmers went in together on a piece of equipment that everyone shared. Either way, farmers paid to have their raw crops turned into something more valuable. The researchers at the University of Minnesota who want to bring a portable biofuel system to Madelia are hoping to repeat that history. Their technology, called microwave pyrolysis, is set to be Madelia’s first shot at making local energy.

The system is both simple and delightfully clever. Pyrolysis is all about breaking down plants and other matter into a form better suited to usable commercial energy. Grasses, stalks, manure—any kind of organic material—goes in. That stuff gets heated to almost 950 degrees Fahrenheit in an oxygen-free environment, thus releasing a host of volatile gases. Condense the gas, and you get a liquid fuel. There are several ways to heat up biomass, but the university’s system is special because it relies on microwaves, stronger versions of the same technology you use to cook popcorn and leftover pizza.

It’s a handy method, because it’s already proven technology—easy to use and cheap to construct. Microwaves also make the entire biofuel production process simpler. Usually, before any biomass can be turned into fuel, it has to be ground into tiny pieces to make sure every bit can be evenly heated at the same time, but microwaves heat up the center of a solid object just fine.

In addition, there’s money to be saved in shipping costs. Moving biomass around isn’t very efficient. Organic material is generally bulky and not very energy dense. Transporting a ton of prairie grasses uses as much energy and costs as much money as transporting a ton of oil, but you get more energy out of the oil. By using microwaves—a heating technology that’s lightweight and can be scaled down to the size of a small camper trailer—the University of Minnesota hit on a way to make pyrolysis portable and bring the fuel factory to the farm. There, each farmer can load up the pyrolysis machine and produce a couple of different products on site. Batch process test runs in the lab took as few as fifteen minutes.

What the farmers get out is useful stuff. Fuel is the main product of microwave pyrolysis. The university’s system does produce enough combustible gas that, once started, it can power itself. In general, though, what you’re making is a liquid called biogas. It’s useable as is, fresh out of the tap, but for best results, it really needs a bit of cleaning up. Any engine will run on fresh biogas, but over time the acidic fuel would tear the engine apart. The university researchers are still working on methods to make biogas compatible with cars, but in the meantime, the stuff can be used in place of home heating oil or sold as a replacement for industrial petroleum.

In the fall test run of the microwave pyrolysis machine, the University of Michigan researchers found some problems with the syngas-powered generator, but they're going to return to Madelia this summer to test the system again with a new generator.

Biogas is not the only important product to come out of the system. Back up to the head of the production line, and you’ll find another output—one that can reduce the quantity of CO2 in the atmosphere and might be able to boost plant growth, too. When biomass is heated by microwaves, the parts that don’t turn into fuel transform into something akin to charcoal. Called biochar, it’s a bit different from standard barbecue briquettes, thanks to the oxygen-free environment where pyrolysis happens.


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