In the search for cellulosic feedstocks, one source seems to be rising to the top in the nation's Corn Belt: corncobs. Why cobs? Why now? They're available. They're transportable. And they are politically correct.

Just ask James Sturdevant, who is heading up his own cob-collection campaign at the POET biorefinery in Emmetsburg, IA. He's responsible for taking the company's existing corn-based ethanol plant in Emmetsburg and turning it into a facility that produces cellulosic ethanol from corncobs as well as corn-based ethanol.

“Our motto is, no cob left behind,” says Sturdevant, director of Project Liberty, POET's cellulosic project. “We envision that every corn farmer will eventually be collecting cobs.”

POET, the nation's largest ethanol producer, received an 80-million-dollar grant from the U.S. Department of Energy to convert its existing corn-based ethanol plant in Emmetsburg to an integrated corn- and cob-based ethanol biorefinery. Once complete, the facility will produce 125 million gallons of ethanol per year. Of that, 25 million gallons will be from corn fiber and corncobs.

Sturdevant says residue left from corn is a logical source of cellulose for POET, whose plants are located throughout the Corn Belt. “Our ethanol plants are surrounded by cornfields,” he says. “What is the most prevalent cellulosic feedstock sitting around? It is corn residue.”

Corn residue, also known as stover, consists of stalks, husks and cobs that are left on the field after the corn grain is harvested. Stover provides the soil with nutrients and helps prevent erosion. However, most of the nutrients reside in the stalks and husks as opposed to the cob.

“We strongly believe you can remove only the cobs without a negative environmental impact,” Sturdevant says. “And frankly, you can make more ethanol from corncobs than you can from the stalks.”

He says that if cobs were collected on our nation's existing corn acres, an additional 5 billion gallons of ethanol could be generated annually. However, only a handful of farmers harvest corncobs.

Sturdevant says one reason is because equipment to harvest cobs on a commercial scale has not been available. POET has enlisted the help of more than a dozen equipment companies, including the majors, to develop harvesting solutions that make cob collection feasible for farmers. For the most part, that means one-pass equipment.

POET recently held a field day to give farmers and journalists a sneak peek at some of the equipment the industry has been developing. More than a dozen companies displayed prototypes to harvest cobs during the same field pass as corn grain harvesting. Farmers attending were asked to consider harvesting cobs for the 25-million-gallon plant, scheduled to go online in 2011.

“We view the 2009 harvest as the stage where there will be many farmer opportunities for commercial cob harvesting,” Sturdevant says. “There will be cob harvest systems available for sale or lease.”

Under POET's plan, farmers will collect the cobs, and POET or a third party will pick them up and transport them to the Emmetsburg biorefinery, where they will be converted to ethanol.

Three ways to collect cobs at the same time as corn were showcased at the event. Here's a look at each of these methods along with the equipment being designed to support each method.

Concept 1 Corn Cob Mix

IN THIS COLLECTION approach, an existing combine is outfitted with specialty sieves and chaffers that enable it to harvest a mixture of both corn and cobs. The mixture collects in the combine grain tank and is hauled to the side of the field for separation. A separator screens the corn from the cobs. Clean grain can be augered to a semitrailer and cobs can be piled on the ground.

Advantage: This method allows farmers to use their existing combine to collect cobs just by changing out a few internal parts in the combine separator for efficient threshing and separating. The separator inside in the combine is adjusted to collect cob as well as grain, and both go in the combine grain tank. No apparatus is required to follow the combine to separate the grain from the cobs.

Disadvantage: The method requires separation equipment at a bin site or at the edge of the field to separate the cobs from the grain.

Concept 2 Towable whole-cob collection

WITH THIS APPROACH, whole cobs are collected in a wagon-style cob harvester that is pulled behind the combine. The combine harvests clean grain as usual and holds it in the combine clean grain bin. Straw choppers on the combine are disengaged to allow the leftover crop material to drop onto a belt that conveys the material to the cob harvester wagon. A separator inside the wagon separates the cobs from the stalks, husks, shucks, leaves and chaff. Cobs stay in the wagon, and the remaining crop material is distributed on the field.

Advantage: In-cab controls enable the operator to transfer cobs to a grain wagon in the field during harvest or dump them in piles at the end of the field.

Disadvantage: It requires installation of in-cab controls and an OEM-approved hitch.

Concept 3 Dual-stream harvester

IN THIS METHOD, a device attached to the back of the combine does the separation, and a tractor alongside the combine pulls a collection wagon. A separator inside the attachment separates cobs from the rest of the stover and delivers the cobs to the collection wagon.

The prototype harvester is able to harvest grain and biomass in two separate streams. The non-cob stover can either be collected in a wagon or distributed over the field. With a flip of a switch, a farmer can switch from conventional harvest to activating the attached device to collect biomass.

Advantage: The method gives the flexibility to move from grain to biomass or field to field with no modification and virtually no slowdown. Price could be lower than that of the pull-behind units.

Disadvantage: It is the furthest from commercial development.

Cob collector FAQs

JAMES STURDEVANT, director of the POET Biorefinery's project to produce cellulosic ethanol from corncobs, answers the most frequently asked questions about project.

What can farmers expect to be paid for corncobs? Farmers will be paid between $30 and $60 per ton. Final pricing will be worked out as equipment becomes commercially available.

How will cobs be stored? On the ground, placed in piles at the edge of the field.

How will cobs be transported to the biorefinery? POET or a third party will pick up the cobs and haul them to the plant.

Will cob harvesting slow the corn grain harvest? Harvesting corncobs and corn grain will be slower than harvesting corn grain alone. The additional time will vary, depending on the cob harvest method employed, in-field transportation, and other variables. One of the main goals of the equipment manufacturers has been to develop machinery that will not have a significant impact on harvest time.

Will cob removal impact the soil? The impact on soil quality will be minimal. Cobs account for only 7.5% of the entire corn plant (which includes grain, stalks, leaves, husks, tassels, etc.), according to research by Iowa State University. Cobs contain very low amounts of nitrogen, phosphorous, and potassium. A recent USDA study shows cobs contain 2 to 3% of the measured nutrients of the above-ground corn plant.

How many cobs will be needed? The cellulosic portion of the Emmetsburg, IA, facility will require 750 to 850 tons of cobs and fiber every day. Cobs will make up to 60% of the total (450 to 500 tons) with the rest coming from the kernel fiber.