Nebraska Corncob Harvesters

Thirty-four-year-old twins from Nebraska invented the Residue Recovery System, a custom-made biomass collection system for combines that harvests and stores whole corncobs separately from the grain in a single pass through the field.
By Ron Kotrba
Ty and Jay Stukenholtz are inventors. They're also identical-twin brothers. The differences in appearance between the two may be hard to see, but once they speak it's easier to distinguish one from the other. Ty is soft-spoken and responds quickly while Jay speaks in a deeper tone, his responses taking a little longer as if he's battling the profundity of his own thoughts. Raised on their family's 350-acre farm outside of Nebraska City, Neb.-land they still work today-the 34-year-olds each hold an agricultural engineering degree from the University of Nebraska. Ty and Jay graduated in 1997. With their educational training and farming experience, the Stukenholtz brothers know all about harvesting corn. Now they know even more about corncob harvesting.

Soon after graduating from the university, Ty's and Jay's inventiveness materialized. Their ingenuity eventually turned into a rather lucrative custom-harvest business, raking in corn and whole corncobs in the same time it would take others to harvest just the grain. Their invention is a custom-built add-on that can be used with virtually any combine on the market. Its purpose is to effectively separate the corncobs from the stalks and leaves during the harvest, keeping the cobs separate in the combine's onboard storage. It's called the Residue Recovery System, a patented and trademarked ensemble of equipment they originally built to collect and sell corncobs to a furfural plant outside of Omaha, Neb. Furfural is a liquid aldehyde made from corncobs and similar agriculture residues, and is used as an industrial solvent.

Ty relates the progression of events that took place after he and his brother graduated from college. "The first two years we were back from college our dad harvested on the family farm," he says. "Then it got rented out, so we didn't have anyplace to harvest." It wasn't going to be easy for them to refine their design with no land to work. That prompted the two to search for custom-harvest acres so they could keep their project going. Finding that special farmer willing to allow experimental equipment runs on their land was challenging. "We were fortunate enough to find one with a couple of thousand acres of corn that we could run over," Ty says. "It helped get the bugs out of our design." The Stukenholtz brothers harvested corn within two miles of the cob processing plant in Omaha using their cob collection system. "We ended up getting between $40 and $50 an acre just for the cobs, so compare that to a $20 or $25-an-acre custom rate and it's pretty lucrative," he says.

With the family farmland rented to another farmer, the brothers custom-harvested from 1999 to 2004. Using their single-pass harvesting invention, the Stukenholtz brothers were able to undercut other custom harvest bids by amassing the dense cobs and selling them to markets such as the furfural plant or ruminant feed markets. The farmers weren't going to miss the cobs; they just wanted the grain. According to the Stukenholtz brothers, cobs are the least valuable component in the corn-crop residue. The farmers that they are working with plant corn-on-corn, meaning crops are not rotated seasonally. Cob piles at the edge of the fields aren't always completely cleaned up by harvest's end, and when the next year's corn crop starts coming in, farmers have difficulties in areas where cobs were left over winter. "It ties up the nitrogen," Jay says. "As much as the cost of the fertilizer is, especially if it keeps going up, and if it takes extra fertilizer to break down the lignin in the corncob to make it into a usable nutrient, that offsets the value in a corn-on-corn rotation," he says. "The cobs are out there every year-it might be beneficial to remove them."

The Invention
Another farmer, who was working with the Omaha furfural plant, designed a wagon to be pulled behind a combine that cleaned the corncobs out of the stover. "They had a hard time making it work," Ty says. "Eventually they got some of the bugs out, but from our experience, pulling a wagon in our part of the country-anywhere really-there just had to be a better way." There was one year when all the brothers did was separate cobs via pull-behind wagons, but that didn't match the efficiency of typical corn-harvesting combines. "That's when we undertook our project," Ty says. "The intent was to build a machine that could run in the hills of southeast Nebraska."

Because rotary combines make up a vast majority of combines marketed in the United States today, most of the Stukenholtz's biomass collection systems have been tailored for rotary combines. The Residue Recovery System consists of what's trademarked the CleanBoot and the TopTank.

"The CleanBoot typically contains a sieve and two blowers," Ty tells Biomass Magazine. One fan is used for cleaning the lighter, fluffier leaves and stalks from the denser cobs; the other blower is used to transport material to the TopTank. "The blower fan is downstream from a Venturi," he says. A Venturi effect, named for Italian physicist Giovanni Battista Venturi, is created when airflow passes through a constricted area and pressure on the inlet side is increased while pressure on the downwind side of the Venturi decreases, creating a vacuum-like environment. "It's unlike anything else I've ever seen," Ty continues. "It can take a tremendous amount of material and blow it into the tank, and it doesn't take a lot of power. It's taken quite a few years to get it ironed out to where we are now."

Just as their voices are unique, so are the roles each twin plays in the ongoing development of the Residue Recovery System. For example, Jay handles the blowers and CleanBoot on the back-end of the combine, while Ty focuses on the TopTank and grain extension on top of the harvester. The TopTank holds 3,000 pounds of cobs, so it's sized at about 80 percent of a combine's onboard grain storage tank. Thus, harvesters with a 300-bushel grain tank would be outfitted with a 300-cubic-feet cob tank, which only takes about half-a-minute to unload once it's full. Patent-pending Autofold technology also allows the operator to collapse the storage bin from inside the cab. With all of the work the Stukenholtz brothers have done with corncob harvesting, Ty still admits, "Cobs are not an exact science."

Planning Ahead
After 10 years of refining and tweaking their invention and supplying a dozen or more custom-engineered collection systems to a smattering of farmers and agribusinesses in the Midwest, the Stukenholtz brothers and their new business partner Beth Pihlblad prepare to take this implement to the next level. Pihlblad was introduced to the Stukenholtz's through a cousin who had been working with them early in the development of their invention.

Pihlblad herself was immersed in renewables, working with a recycling company that was using woody biomass to cofire with coal. "I became more curious about their invention, so I contacted them last fall and that's when they told me their story," she says. "I was introducing them to the larger potential of what they created." Pihlblad says the Stukenholtzes knew of the emerging biomass utilization industries such as biomass-to-power, cellulosic ethanol and the "green" chemistry movement, but didn't realize how big an effort was being amassed in that direction.

Shortly after Jan. 1, Ty, Jay and Pihlblad formed a company, Ceres Agriculture Consultants, to promote their machinery and harvesting services, and to build relationships in the industry. The brothers started another company in 2001, Cobco Manufacturing Inc., which they formed to help market prototypes of their equipment, harvested cobs and other forms of biomass to end users. "We've supplied two coal plants with cobs-one was at the University of Missouri at Columbia-and we've worked with a public utility company supplying them with cobs," Ty says. Now, Ceres Agriculture Consultants will take a lead role in promoting renewable energy projects development for its business partners. Cobco will likely be transformed into what Pihlblad calls a "fuel processing and trucking/distribution company." Ty explains the rationale behind this move. "A lot of the markets we have for cobs, which have sustained our project, are 250 miles away," he says. "We've already got the trucks we need to get started … We would have to expand a lot, but we've got a start anyway."

Amidst all of these activities-developing renewable energy projects, agricultural consulting, custom-harvesting, and fuel processing and distribution-one wonders what will become of the Stukenholtz's cob collection system? "We still need to refine the engineering and partner with a manufacturer," Pihlblad tells Biomass Magazine. An aftermarket equipment maker will likely be the first partner in the manufacturing of this machinery, Jay says. "Once it appears the market is big enough, the OEMs will be more likely to pick it up."

Ty says deciding exactly how large the market is for their invention remains a challenge. "We're having a hard time trying to figure it out," he says. "We are going to need somewhere between a couple of these and 500. That's the biggest challenge here-moving from the prototype stage with custom-built machines for specific applications to a product that has manufacturability."

Until a manufacturing agreement is set, the brothers will continue to test and refine their creation for different applications. This fall they will harvest 60 acres of soybeans and test their invention collecting the soybean pods. The residue sizes make the biggest difference when configuring each custom-built apparatus. "Change the air, change the sieve size, and if you have to, change the whole sieve," Jay says. "That's what we have to do for different residues." The twins are especially interested in trying their device on wheat straw, Ty says. "There's a large push-especially in the cellulosic ethanol industry-to use wheat straw, largely because wheat is grown in drier climates," he says. "But with wheat straw there are density issues that will require a larger TopTank on the combine."

Pihlblad says she will concentrate on building momentum in the emerging biomass industries for the cob collection system they've developed. "We'll be focusing on education within the industry," she says. "Farmers are going to have to see the value-the intrinsic value imbedded, and how much money they can make on this. Our focus until next spring will be education and awareness, and generating momentum-we need momentum. We need farmers to be asking, ‘Where can I use this? Where can I buy it? What are its applications?'" Moreover, Pihlblad says what's really needed are outlets for all of the available biomass materials.

Ron Kotrba is a Biomass Magazine staff writer. Reach him at or (701) 746-8385.