For Ty and Jay Stukenholtz, hemp harvesting isn't their first rodeo. The brothers, farmers and engineers have been designing and inventing biomass harvesting equipment for more than 20 years.
Getting their start designing machines to harvest corn residue, they've also ventured into harvesting parts of the corn plant for value-added products — and equipment for harvesting wildflower and native grass seed.
So, it may not be surprising to learn that their latest invention, the FarmMax Interceptor, a combine attachment designed to harvest all main components of a hemp plant, didn't exist before October 2019. Yet by spring 2020, the Stukenholtz brothers are commercialized to presell units to growers for fall 2020.
However, their involvement in hemp goes back to 2015, when they met with growers in Tennessee who were seeking a way to efficiently harvest hemp. After researching current hand-harvesting methods and industry needs through conversations with growers in Colorado and Kansas, the idea for the Interceptor took shape.
"Since 2015, we've been behind the scenes trying to figure out what we needed to do to accomplish this," Ty says. "The other side of it was figuring out how to pay for it."
In 2019, with the help of a Nebraska Innovation Fund Prototype Grant through the Nebraska Department of Economic Development, they began to build the machine.
Streamlined for hemp
While much of the design was inspired by their previous work, Ty notes the Interceptor is streamlined specifically for industrial hemp harvest.
"On a rotary combine, like a John Deere or Case IH, one of the challenges is they put the chaff and the discharge from the rotor together," he says. "We isolated the chaff, so we could collect it and not blow anything out. Methods that use a lot of air can blow out a trichome if they don’t contain the material. We're trying to capture 100% of it — even the smallest hemp particles. We've made it harvest a minuscule part of the plant through containment."
Trichomes range in size from 10 to 100 micrometers, or microns. For reference, one micrometer is one one-millionth of a meter. These tiny particles in the hemp flower contain cannabidiol (CBD) — a key end-use product in the hemp market.
However, the stem and seed also have value. While it isn't yet known what markets will be best-suited and available to growers in the Midwest, having the flexibility to harvest all parts of the plant may help meet diverse market needs.
The Interceptor latches on to a specially designed frame mounted on the undercarriage of the combine, allowing for quick attaching and detaching. It collects chaff and stems from the rotor, allowing seed to go to the grain tank, while stems and flowers are separated. Stems are discharged in windrows on the ground, and flowers are blown from a spout onto a wagon.
The Interceptor uses a two-stage fan system — a beater forces material into the airstream, while a blower charges the airstream that pushes the material through the Interceptor.
Jay Stukenholtz notes that when harvesting hemp with the Interceptor, the combine usually is set to a more aggressive rotor speed. The appropriate rotor speed also depends on how dry the hemp crop is.
"For hemp, you close the chaffer all the way down and separate the seed using air," Jay says. "Stems go out the rotor, seed goes to the grain tank, and the amount of material you want to collect through the Interceptor is basically what's left.
"If you want to collect more, you can turn up the rotor speed and push more through the concaves. Or you can slow it way down. I've had the rotor speed as high as 1,000 RPMs, and down to 300, so there's a big range."
Bringing in the harvest
One of the biggest advantages is the Interceptor provides a way to harvest a hemp crop in a timely manner. Beth Stukenholtz, a biologist and the brothers' business partner since 2006 who manages communications and business development for FarmMax, notes that according to USDA guidelines, producers are required to harvest no later than 15 days after the crop is tested for THC (tetrahydrocannabinol), which must be 0.3% or less.
"If your product is green, you still have to go into the field," Beth says. "That's why ideally there would be drying technology or other processing married to what we do. This would preserve the quality of the material as it comes straight out of the field. The material wouldn't be handled repeatedly, losing precious elements each time it's moved or touched."
FarmMax will be working with Nebraska-based John Deere dealer Platte Valley Equipment this year to sell, install and service its system. It also is looking at available dryer technologies that would work well with the Interceptor to recommend.
For the time being, the Interceptor attachment is being made solely for John Deere S series combines using draper heads, although Ty notes they plan to work with other makes and models of combines down the road.
The Stukenholtzes have considered designing their own wagon to accompany the Interceptor, but for now, they've been using a high-lift dump wagon with an extended drawbar to accommodate the air chute. They're also developing a yield monitor system to keep track of yield in flowers per acre in a given field.
Ty, Jay and Beth will be involved with Platte Valley Equipment for the first limited commercial run planned for this fall. As the engineers, Ty and Jay understand the necessity of following the performance of the product in real time.
"Combines are highly specialized and complicated machines," Jay says. "We know we can't step back yet and let someone else take the reins, at least not until Platte Valley is comfortable and so are we. This is all new, and we want this to succeed."