Drying corn with ground heat
All grain farmers want a low-cost and energy efficient drying system that’s easy to use and keeps the grain safe throughout the drying process. Propane, natural gas and air drying are the most common methods.
Eric Jellum raises corn and soybeans on a small farm in northern Iowa and had been using natural air for grain drying. He had a ground source heat pump for the house and started tinkering with this system to dry corn in the bin.
"It starts with the ground heat exchanger which is buried 8 feet deep and runs for 800 feet," he says. "There’s a small circulating pump that circulates an antifreeze solution continuously and that surfaces into some heat exchangers in the air flow stream for the fan that blows the air under the drying floor of the bin."
After three years of drying grain this way, Jellum found the ground heat was just enough to lower the relative humidity to reach the target corn moisture content. He was also able to drop the size of the air pump and extend the drying time through the winter without any grain quality issues.
"For one thing, you’ve got continuous air flow so any hot spots that might develop are kind of nipped in the bud," says Jellum. "But the condition otherwise, you know, when you dry real slow, you get better test weight, you get less checking of the corn, so it’s a real gentle way to dry."
Generally speaking, the energy cost for the ground heat is just 2%-3% of what the cost would be using LP at one-dollar-per-gallon.