David Grewell flipped a switch and one of the ultrasonic machines in his Iowa State University laboratory pumped out high-frequency sound waves.
Those 20 kilohertz waves were too high for human hearing. But put the machine's circular, metal horn in a bucket of water and the sound waves get the liquid bubbling with a loud hiss. Then put a sheet of aluminum foil in the bucket and watch the power of cavitation -- the formation and collapse of bubbles -- as it marks the metal with tiny dimples and starts to tear it apart.
If a few seconds of ultrasonic treatment can do that to metal, think what ultrasonics can do to corn kernels, said Grewell, an Iowa State assistant professor of agricultural and biosystems engineering.
It turns out ultrasonics can do a lot to the corn slurry that's used to produce ethanol.
Samir Khanal, an Iowa State research assistant professor of environmental engineering, said the conventional dry-milling process that's used to make ethanol doesn't convert all the starch in corn kernels into the simple sugars that can be fermented into ethanol. A team of Iowa State researchers has demonstrated that pre-treating milled corn with ultrasonics can break the corn pieces into even finer particles. That exposes more of the corn's starch to the enzymes that convert starch to simple sugars. The research team also plans to see if ultrasonics releases some sugars from the fibrous, cellulosic material in corn.
Grewell said ultrasonic treatment in laboratory experiments has increased corn's release rates of sugars by nearly 30 percent. And that could mean each bushel of corn that goes into an ethanol plant could more efficiently produce ethanol for your car's fuel tank.
"This seems to work very well," Grewell said. "We're releasing more of the corn's stored energy in a shorter period of time with less energy consumption."
The discovery has led to a patent application and a one-year provisional patent for immediate commercialization of the technology.
Grewell is directing the research project. Khanal and Hans van Leeuwen, an Iowa State professor of environmental engineering, are also working on the project.
Their research is supported by an $80,519 grant from Iowa State's share of the Grow Iowa Values Fund, the state's economic development fund.
Grewell said the researchers' next step will be to quantify the amount of ethanol produced when corn slurry is treated with ultrasonics. Then the process will be tested at a larger, pilot scale.
Ultrasonics has been used by various industries to join plastics, weld metals, clean surfaces and process liquids. Grewell, in fact, worked for 12 years in research and development for the Branson Ultrasonics Corp. of Danbury, Conn. He said he worked on a variety of ultrasonic applications, everything from freezing strawberries to processing rice.
And now the research goal is to produce more ethanol from corn.
"I think this is the right project at this point in time," Khanal said. "It may reduce the cost of ethanol production and ethanol production may become more efficient."
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