8 billion gallons of fuel from corn crop waste: USDA, Iowa State report confirms potential

Corn stover. It’s that inedible leftover from the corn crop, and if you’ve ever noted how big a corn plant is in comparison to the size of the ear, you know there’s a lot of it.

Traditionally, it’s left on the field, and returns nutrients to the soil as it is broken down by bacteria.

But we’ve known or some time that Nature doesn’t really need all that leftover biomass — in fact, the heavy productivity of corn farmers these days is leaving quite a bit more biomass on the field than the bacteria are used to handling.

And with the technology for producing cellulosic biofuels just now arriving at commercial scale — the question becomes more urgent. Just how much biomass is available.

According to Iowa State University and USDA, the figure look right around 90 million tons of biomass — enough, at 90 gallons per ton (some technologies produce more, others less), that represents right around 8 billion gallons of ethanol. It could of course, be converted to more energy-dense hydrocarbons with resultingly lower yields.

Now – that’s a theoretical limit — in practice, we’d expect to see that many acres of corn stover would not get picked up — just too far from a processing installation. And there are the limitations on the market for ethanol — and there’s the challenge of competing with fossil oil as the incumbent. But, you get the idea.

The work was commissioned by POET-DSM Advanced Biofuels to ensure the sustainability of the joint venture’s plans to build cellulosic ethanol plants and license technology to producers in the U.S. and abroad. The research, by Dr. Doug Karlen with USDA and Dr. Stuart Birrell with ISU, was conducted in fields near Emmetsburg, Iowa, the site of Project LIBERTY, POET-DSM’s 20 million-gallon-per-year cellulosic ethanol plant currently under construction. The facility will use corn-crop residue – cobs, leaves, husk and some stalk – to produce renewable fuel. It is slated to come online in early 2014.

The research, now in its fifth year, evaluated the possible effects of biomass removal on soil nutrient levels and grain yields over various rates of removal. POET-DSM’s proposed rate of removal is approximately 1 ton per acre, which is 20-25 percent of the above-ground biomass.
“In summary, both grain yields and soil nutrient levels were not significantly affected by stover harvest treatments,” Birrell said in a research summary.

Fields with yields above 175 bushels per acre could remove up to 2 tons of biomass per acre, according to Birrell and Karlen. Based on the data, POET-DSM recommends no changes in nitrogen or phosphorous applications, due to residue removal. Some biomass providers could benefit from adding a small amount of potassium.

“As yields increase, I’m seeing more and more biomass on my field,” said Bruce Nelson, an area farmer who harvests biomass on both his own farm and others’ fields. “Removing some of that material has actually improved how my farm operates. It’s a great opportunity for farmers.”

“This latest data is consistent with what we’ve seen in previous years, and we’re glad that biomass harvesting continues to be an attractive opportunity for farmers,” said Adam Wirt, Biomass Logistics Director for POET Biomass, which handles biomass program management for Project LIBERTY. “Opportunities for today’s farmers are evolving right before our eyes. It’s exciting to be part of it.”

Project LIBERTY is projected to provide about $20 million in income to Emmetsburg-area farmers annually for the corn-crop biomass that will be used in cellulosic ethanol production.

Construction progress at Project LIBERTY continues to move forward on schedule. POET-DSM has initiated discussions with U.S. ethanol producers regarding licensing the joint venture’s cellulosic ethanol production technology.

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