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Corn+Soybean Digest

Collect Cobs

Imagine leaving $30/acre or more in the field when you harvest corn. That's about how much the cobs are worth when harvested as a “second crop” in the same harvesting pass.

Ty and Jay Stukenholtz, Nebraska City, NE, have designed and are now building a combine-mounted system to capture this bonus crop. And by the way, nothing is towed, which would slow down grain harvest.

These twin brothers began working on their residue recovery system shortly after graduating with ag engineering degrees from the University of Nebraska about 10 years ago. The family farm south of Nebraska City became the laboratory for their first prototypes.

Speed is money to farmers,Ty says. He and Jay kept that in mind when they designed a system that collects all or any fraction of the residues coming out the back of a combine. Harvesting the residues right along with, but separate from, the grain causes little if any fall-off in field efficiency, Ty says. “We've run side-by-side (one combine with the residue collection system and the other without) and have seen no difference, if everything is working,” Ty says.

The Stukenholtzes say their system works not just in corn but other crops, including soybeans and even such non-mainstream crops as native grass and wildflower seed. The system can recover all or any fraction of the combine tailings,depending on how it's adjusted.

Cobs account for about 20%of the non-grain portion of a corn crop, Ty says. That leaves plenty of residues on the field for erosion control. In fact, the Natural Resources and Conservation Service (NRCS), by chance, checked residue cover on a field that was harvested with the residue recovery system. The NRCS sent the Stukenholtzes a letter commending them on the amount of residue cover.

Along with making the residue recovery systems available to others, the Stukenholtzes operate two custom combines equipped with the systems in Nebraska and Iowa. (Jay was out with the crew on the day of this interview.)

They say they can outfit about any make of combine, whether rotary or conventional. Most are mid-to large-capacity rotary combines.

While they are making the units by special order now, Ty says, the next step for them is to find a manufacturer who can mass produce and market the units as after market equipment. He estimates there is a market for as many as 300 machines within a 60-mile radius in some areas.

Cobs for roughage in cattle rations are the biggest collected residue market right now, bringing $50-plus/ton, according to Ty. About ¾ ton/acre of cobs are recovered from an average corn crop,he says. But, cattle feeders aren't the only market.

The Stukenholtzes and friend Beth Pihlblad have formed Ceres Agriculture Consultants to market their recovery system and to identify and develop markets for cobs and other fractions of the tailings collected by the system. Other markets include cobs for blends at 10-50% with coal at coal-fired power plants. The University of Missouri power plant at Columbia is one of two Missouri trial outlets for cobs from Ceres.

Cellulosic ethanol production is yet another potential market, says Pihlblad. Rather than turning cobs into ethanol, they are used in a gasification process to produce energy that drives ethanol production from cellulosic materials such as switch grass and corn stover, she says. “That market is going to take some time,” says Pihlblad, who develops markets for the collected residues. “I'm trying to help fill the market base.”

U.S. Department of Energy grants for developing a cellulosic ethanol industry have largely ignored the feedstock end, Ty and Pihlblad say. Developing a system that can provide a reliable volume of cellulosic ethanol feedstock needs more attention, they say.

The Stukenholtz brothers' residue recovery system consists mainly of what they call a Clean Boot at the back of the combine (blower system that separates cobs from other combine tailings) and a Top Tank (bin sitting above the combine grain bin). The Clean Boot blower system creates a vacuum in a duct leading to the Top Tank. Collected residues are sucked from the Clean Boot, through the duct, to the Top Tank.

The Top Tank holds roughly the volume of cobs produced by the amount of corn needed to fill the combine grain tank. That way, the Top Tank and grain tank are ready for dumping at roughly the same time.

Again, mindful of time value to farmers, the Stukenholtzes incorporated a Top Tank on the grain cart so the cart can receive both residues and grain from the combine. Operated from controls in the cab, the Top Tank on the combine slides outboard from its position over the grain tank for unloading in 30-40 seconds into the Top Tank on the cart. (The combine Top Tank can also dump directly into a truck.)

Once the residue tank atop the grain cart has been loaded from the combine, it's positioned to the side of the grain cart, out of the way, so the combine can unload grain into the cart. The Top Tanks on the cart and the combine unload by means of an apron floor.

The residue recovery system costs from $30,000 to $40,000, depending on the number of features, such as monitor cameras.

Outfitting a combine with the residue recovery system includes replacing the original equipment manufacturer's grain tank extension with a new extension. The Top Tank for residues is installed above it. In-cab controls allow the combine operator to collapse the grain tank extension and Top Tank for a transport height only about 6 in. higher than a non-modified combine, according to Ty.

Taking the residue recovery system off a combine takes a little more than an hour: 10-15 minutes to remove the Clean Boot and about an hour for the Top Tank, using an overhead crane, Ty says.

Weight-wise, Ty says, the Clean Boot replaces some of the suitcase weights that a combine would otherwise carry. The combined weight of the Top Tank and Clean Boot is about equal to four-row units, he says. So a combine with an eight-row head and the residue recovery system would weigh about as much as a combine with a 12-row head minus the residue recovery system.

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