Farmers weigh stover harvest, land use

Sep 13, 2013

As buzzwords go, “sustainability” rules the day when U.S. farmers question how their operations fit into the big picture of a future carbon economy.

Yet as several cellulosic ethanol companies that use corn stover stand on the verge of commercializing their operations across the Corn Belt and as seed companies work to continue boosting average corn yields in coming years, it won’t be long before producers become intimately familiar with a new set of buzzwords: “residue management.”

Steve Petersen, an Iowa farmer and end-use marketing manager for Monsanto Sustainable Corn Stover Harvest, said he has been harvesting corn stover on his eastern Iowa farm for years.

Some seed researchers claim that future corn hybrids will have the ability to push yields around 300 bushels an acre, possibly as early as 2030.

That’s a lot of biomass. “Even in 2012 with the worst drought since 1988, maybe even since the Dust Bowl, we had an average of 140-bushel yields,” Petersen said during a corn stover harvest seminar last Tuesday ahead of the National Advanced Biofuels Conference in Omaha, NE.

“Some farmers have too much residue left in the soil. It cuts back yields.”

Throughout the Corn Belt, corn stover has emerged as the clear-cut favorite to carry the day as a cellulosic ethanol feedstock because ethanol companies and farmers know the crop.

Poet-DSM is expected to start production as one of the first commercial operations in 2014 and has hundreds of farmers contracted to provide nearly 300,000 tons of stover bales to the plant in Emmetsburg, Iowa.

POET has long-term plans of installing its cellulosic technology at all 27 of its corn-starch-based ethanol plants across the Midwest, and has talked about selling its technology to outside companies.

Simply put, such an expansion of cellulosic ethanol production will require immense amounts of biomass.

Petersen said even those farmers who have no intention of harvesting stover will still have to plan for managing increasing volumes of biomass residue in their fields.

“We need to have some stover on that ground,” he said.

The key will be to develop a harvest system designed to balance the need to leave enough residue in the field with the need to prevent future health problems with the next crop.

“We’re seeing more and more growers going to continuous corn, manure applications and cover crops,” Petersen said.

Petersen has led a study for Monsanto, looking at all aspects of corn stover harvest and addressing farmers’ concerns about fertilizer loss, erosion, yields and a whole host of diseases.

Although nutrient loss from corn stover harvest will vary from field to field, the Monsanto trials have given farmers at least some idea of what stover harvest entails.

Fertilizer loss

On average, Petersen said, stover harvest removed about 39 pounds of fertilizer per ton of biomass. In all, he said, that amounts to about $5 worth of nutrient loss per bale.

During the trials, he said, farmers planted annual ryegrass as a cover crop in between corn rows at a cost of about $30 an acre. This has improved soil health.

“It allowed us to harvest about three tons of stover and it changed the economics dramatically,” Petersen said.

Iowa potential

David Ertl, technology commercialization manager for the Iowa Corn Growers Association, said there is plenty of room in Iowa to generate more money per acre harvesting stover.

However, it may not be for everyone.

“If you’re going to start removing stover from the field, you should strongly consider reducing tillage,” Ertl said.

Typically, harvesting two tons of stover from a field cuts stover cover by about half, he said. Cellulosic ethanol producers, ideally, would benefit from more farmers switching to continuous corn, Ertl said, because of large biomass volumes.

“In a continuous corn situation, you don’t need to apply as much nitrogen when harvesting stover,” he said.

The first generation of cellulosic ethanol plants coming on line in the next few years will produce on a relatively small scale, in the 20- to 30-million-gallon range. In the corn-based ethanol industry, commercial plants typically produce anywhere from 50 million to 100 million gallons a year.

Winston Akoto, global operations and supply chain director for DuPont Pioneer, said that based on his company’s experience in securing biomass contracts for its plant set to launch next year in Nevada, Iowa, first-generation plants will be able to source enough biomass.

“We’re going to have to develop the capability to get enough biomass to produce much bigger plants,” he said, “and that means larger biomass quantity. I’m not sure we’re confident that we can supply a 100-milliongallon plant.”

Perhaps the biggest barrier to convincing more corn farmers to invest in stover harvest is time and whether they can make money.

Scott Weishaar, product manager for environmental solutions at farm-equipment company Vermeer Corp., said farmers face a short harvest window for stover— typically in the range of 15 to 20 days.

For companies such as Poet-DSM, several hundred farmers need to harvest some 300,000 tons of biomass after grain harvest.

“What’s new is the mass collection in a short window,” Weishaar said. “We’re seeing an intensity of farming in areas where it has never been before. For farmers, it’s a new practice. It has been done but on a small scale. It comes down to economics. What does it do to my yields and tillage requirements? When (cellulosic ethanol) plants start taking shape, that’s when farmers say it’s real.” — Todd Neeley, DTN