The Cost Of Grain-Drying

With rising inputs, volatile markets, and now what appears to be a multi-year drought forming, crop growers will be doing all they can to improve yields, save costs, and widen their profit margins.

One area to look into is post-harvest grain-drying.

The best grain-drying happens in the field, and pending a cool, damp summer, most years’ growing seasons are able to suck out much of the moisture from the grain by middle to late October, says Kenneth Hellevang, agricultural engineering professor and Extension engineer for the North Dakota State University in Fargo, N.D. Yet, there’s often a little grain-drying left even on the most ideal years to ensure that bugs and disease don’t ruin the yield in the bin.

“We’re seeing a lot of interest in natural-air drying over the last several years,” Hellevang said. The main difference between natural-air drying and the traditional set-up is the lack of supplemental heat, which uses more energy and therefore costs more.

“Natural-air drying, if properly designed and managed, is the most energy-efficient drying,” Hellevang said. “Adding heat increases drying and shrink cost.”

In fact, over-drying can put a dent of more than $4,000 in a farmer’s profits each season, he adds. Over-drying occurs in less efficient or poorly managed systems.

“Typically, the low-speed centrifugal fan moves the most air flow per horsepower through corn, so is the most efficient,” Hellevang said.

Natural-air drying is very efficient in the spring, as soon as the average overnight temperature rises above 40 degrees Fahrenheit, Hellevang says. However, natural-air drying is not efficient or even effective on very wet grain or at outside temperatures typical of November through March. That’s why producers need to be skilled in managing supplemental heat dryers.

“The energy to remove a pound of water is less at higher temperatures and lower air flow rates,” Hellevang said. “Use the maximum temperature that will not damage the grain.”

The next most efficient system is low-temperature drying, in which the air temperature is increased only incrementally as much as is needed to reduce grain moisture. Hellevang recommends increasing air temperature only five degrees Fahrenheit at a time, and then to use a controller to keep the bin at the minimum effective temperature. However, he warns, as with natural-air drying, low-temperature drying only works well until outdoor temperatures approach freezing.

Overwintering grain-drying requires more heat. The maximum drying rate can be obtained with a shallower bin depth, and temperatures can go up to 160 degrees Fahrenheit, but stirring is a must to protect grain against over-drying.

“Using a higher temperature on the wettest grain reduces energy consumption,” Hellevang said. “A grain turner or inverter reduces over-drying, moisture variation, and excessive kernel temperatures. Increasing the grain flow rate reduces excessive grain temperatures and creates a more uniform grain moisture content coming from the dryer.”

Tom Dorn, Lancaster County Extension educator with the University of Nebraska in Lincoln, Neb., says the best way that producers can detect overheating is by using a probe to check for heat spots with a temperature difference of more than 10 degrees Fahrenheit from the average bin temperature. Growers without a probe can look for condensation forming on the outside surface of the bin roof on a cold day or a musty odor inside the bin. The best solution to overheating is stirring, but the aeration fans can also suffice. Or, Dorn says, producers are better to market the grain early than to over-dry it. For grain that is above 15 percent moisture, the best management practice is to reduce the heat and continue to dry it.

“Half of the equation in preventing spoilage in stored grain is getting the grain cool and keeping it cool,” Dorn said. “If you can’t get it as dry as you’d like, at least keep it cool.”

When using the higher temperatures, cooling may be needed in a different bin.

“In-storage cooling requires rapid cooling and cooler initial grain temperature to limit condensation,” Hellevang said. “Slow cooling saves more energy, but storage problems typically occur near the bin wall.”

There are limitations, though. It’s important to let the grain dry as much naturally in the field, because there really is no cost savings to trying to dry out very wet grain in the bin.

“Dry when it is warmer if possible, since it takes more energy to dry at colder temperatures,” Hellevang said.