Cellulosic ethanol requires efficiently collecting corn stover bales

Source: By Andrea Johnson, For Midwest Producer • Posted: Thursday, March 6, 2014

AMES, Iowa – Corn stover experts have found ways to reduce the cost of bringing corn stover from the field to cellulosic ethanol plants.

A study conducted by DuPont Cellulosic Ethanol and Iowa State University was able to reduce the cost of moving corn stover from $91 per ton to $52 per ton – a reduction of about 43 percent.

The cost of $91 per ton represented the equivalent of over $1 per gallon of ethanol – just for the feedstock logistics cost.

“That’s before you have to pay for the plant, actually run the plant, distribute the fuel and get it ultimately to an end user,” said Matt Darr, Iowa State University associate professor in Agricultural and Biosystems Engineering, who has worked extensively with this project.

Darr said that strategic investments were developed and research was conducted to find ways of reducing the cost of moving corn stover.

A DuPont/Iowa State University multiyear case study on biomass costs found several areas where savings could be achieved:

– Shrinking the production area by using good agronomic information helped producers maximize stover collection;

– Improving baling quality systems, through increased bale density resulted in cost savings; and

– Lean manufacturing strategies focused on reducing the quantity of in-field machinery.

“This is a substantial reduction from where we started to where we are today, in terms of overall costs,” said Darr, speaking during a DuPont Pioneer media event held in February.

“We would say this has been – from our perspective – one of the best partnerships of creating research opportunities and creating material that helps us make new courses at Iowa State University to train the next generation into bio-economy leaders.”

Iowa State University has developed a role of expertise support for bio-refineries. They are providing technical information on all aspects of the corn stover biomass chain from their BioCentury Research Farm near Ames.

The facility is a research and demonstration facility dedicated to biomass production and processing.

Construction is underway for DuPont’s commercial-scale ethanol facility near Nevada, Iowa, and at the POET-DSM Advanced Biofuel cellulosic bio-ethanol plant near Emmetsburg, Iowa.

The DuPont facility is expected to produce 30 million gallons of liquid fuel annually, while the POET facility intends to begin with 20 million gallons of production and ramp up to 25 million gallons.

Darr pointed out that 30 million gallons of production will require 900,000 large square bales, each with a dimension of 3- by 4- by 8-feet, weighing about 1 ton each. The plant will process one bale every 30 seconds, and require 25,000 semi-loads of delivered bales annually. Over 300 tractors are involved in moving 900,000 bales annually, too.

“It’s a massive endeavor to make this work on an industrial scale,” he said.

The logistics of moving 900,000 large square bales requires balancing producer benefits with sustainability and maintaining profitability for stakeholders, he said. In addition, custom harvest crews need to stay profitable, and the cellulosic ethanol plant needs economic sustainability.

Another concern is the production of ash. A 30-million gallon plant could produce up to 45,000 tons of ash – primarily from soil that is baled with the stover. The corn stover industry is quickly finding ways to reduce ash in corn stover.

About two tons – or two bales of corn stover – are collected per acre. That leaves about 50 percent of the stover on the field. Darr said the goal of harvesting a clean two tons of stover per acre is difficult, because of soil getting into the bale.

Darr expects to see commercialization of new machine forms to harvest corn stover. Running a baler behind the combine or using a windrowing corn header hold potential. The baler or the windrower corn header reduce contamination by soil and eliminate the need for a windrower pass.

Challenges include dealing with high feedstock moisture content that requires special handling. The whole system becomes more complicated at a time when farmers want to work quickly to bring in the grain harvest.

Once the bales are made, they need to be stacked and some type of covering needs to be fastened over the top to maintain quality through the winter.

The corn stover community has reduced fuel use from field to plant to about 2 gallons per ton. That same ton of stover will produce about 80 gallons of fuel

“When you look at the data-driven approaches that we’ve done for this, we’re already seeing transfer of that technology into the forage sector, the sugarcane sector, the crop harvesting sector, and a lot of sectors of agriculture – outside of corn in the Midwest – that deal with logistic-based issues,” said Darr.