Seminar focuses on corn stover as a biofuel feedstock

By Anna Simet | September 10, 2013

As a precursor to the National Advanced Biofuel Conference and Expo in Omaha, Neb., Sept. 10-12, the Corn Stover Harvest & Transport Seminar hashed over the technological, logistical and environmental issues of using corn stover as an advanced biofuel feedstock.

Brian Wienhold, researcher leader and soil scientist at the USDA Agricultural Research Service, discussed concerns associated with residual removal, including loss of soil organic matter and essential plant nutrients, and increased wind erosion.

Wienhold, who has worked in residue management for 30 years, said it’s been known for a long time that residue management on the soil surface is essential for reducing erosion. “The point that gets lost is that [when loss occurs] it removes soil organic matter,” he said.

Recognizing the technological advances that have occurred in ag operations over the last several decades, Steve Peterson, farmer and end use marketing manager for Monsanto, compared the U.S. corn crop from 1970 to 2010. In 1970, 66.9 million acres of corn was planted, with an average yield of 72 bushels per acre and 18,000 plants per acre. In 2010, 88.2 million acres of corn was planted, with average yields of 153 bushels per acre and 30,000 plants per acre, according to Peterson.

“[With high yields] Corn stover becomes a challenge, but also an opportunity,” Peterson said, adding that large amounts of material left on the ground can negatively impact yields for corn on corn.

In a survey conducted by Monsanto, 500 farmers answered questions about corn stover management, and about 80 percent said stover was becoming a real issue on their farm, according to Peterson, meaning they are spending more time and more money to manage residue.

The U.S. corn crop could potentially reach 100 million acres in 2030 with 300 bushels per acre, from Peterson’s perspective. While all of the stover can’t be left on the ground, there is uncertainty and risks surrounding improper removal. How much should be left on the soil is dependent on many factors, which are both location specific and farmer controlled, he said.

Peterson also discussed the potential benefits in planting cover crops such as rye grass to ensure soil protection and sustainability while allowing for greater amounts of stover harvest. Using rye grass can lead to increases in corn yields in subsequent years, he said, and although it may change, adding it to soybeans currently costs about $30 an acre.

David Ertl, technology commercialization manager for Iowa Corn, said that Iowa corn is favorable for offering farmers the opportunity to make more money off of an acre, but emphasized the importance of sustainable residue management.

 Ertl emphasized the potential significance of reducing tillage when increasing corn stover removal. “I’d strongly advise farmers who [remove stover], to strongly consider reducing some of the tillage…They can reduce passes through the field, reduce energy consumption and less exposure of the soil, or erosion. The less tillage you do, the more stover can be removed.”

Combining [changes in] tillage practices with stover harvest can result in essentially no change in the cover on the surface, Ertl said. “That’s an important message—you have to change other practices when you’re harvesting stover; you can’t just keep everything the same and expect it to be good.”

Ertl said that stover removal may increase yields of corn on corn in many cases; removal on lighter soils in dryer locations, where water is a limitation, could have a negative effect, but removals on heavy soils tend to improve yields. There are many variables that come into play when considering how much stover can be sustainably removed, he said, including tillage, slope, rotation, cover crops, corn yield level and manure application.  

The best opportunity for stover removal, Ertl summarized, is in fields that are non-sloping and high-yielding, with minimal or no-till, continuous corn growth and cover crop application. “If you were to do this kind of farming, you’d almost have to do stover removal to manage residue.”

Adding that it’s very difficult to make stover removal generalizations, Ertl said there are tools are being developed to determine precise amounts of stover than can be removed, based on inputs entered by farmers.

Other panels during the Corn Stove Harvest & Transport Summit explored economics of corn stover collection and its potential value, as well as residue procurement for commercial-scale cellulosic ethanol projects, including Poet’s Project Liberty and DuPont Cellulosic.