Kernel of Opportunity: Corn Fiber-to-Ethanol

In testifying at the U.S. EPA hearing in early December, I said that the renewable fuels standard revisions in 2007 (RFS2) contributed to the biofuels industry’s “uniquely high rate of technology innovation and technology adoption.”  In light of this fact, any adjustments to the renewable volume obligations will certainly stifle emerging technologies that could transform our transportation fuel supply. First on my list of those technologies is corn kernel fiber conversion to cellulosic ethanol. This technology alone holds the potential to produce more than 1 billion gallons of cellulosic ethanol at existing dry-grind plants. This would go a long way towards meeting the cellulosic targets set by RFS2. Cellulosic ethanol production at dry-grind plants also holds the potential to further reduce the greenhouse gas emissions from ethanol production, which are already significantly lower than those of gasoline.

Shortly after the passage of the Energy Independence and Security Act of 2007, the National Corn-to-Ethanol Research Center started development of corn kernel fiber-to-ethanol technologies. Initially, NCERC worked on advancing fiber characterization and pretreatment technologies, then followed up in 2009 with work on the fermentation process. This work was supported with experimental enzymes from Novozymes. In parallel, private technology providers have also advanced the technology, which is now entering commercialization. The current state of the technology would produce approximately 10 percent more ethanol at a dry-grind facility from fiber in the corn pericarp and corn flour using regular unmodified yeast (S. cerevisiae). If genetically enhanced yeast is used, pending regulatory approval, the yield increases could top 15 percent. Some variable costs and longer fermentation times should easily be compensated for by the prospects of cellulosic RIN (renewable identification number) payments under RFS2. The resulting technology pull is exactly what the policy instrument intended to achieve.  

With the cellulosic RIN, though, comes a certain amount of risk to the producer and the RIN buyer. Both parties need to ensure that the RIN is generated validly, since the cellulosic (D3 RINs) and corn ethanol (D6 RINs) are produced concurrently. In a discussion with an obligated party active in the RIN market, the party said that while his company neither bought nor sold D3 RINs, he knew of another that tried to sell D3 RINs in the marketplace. Potential buyers questioned the validity and almost refused to acknowledge the existence of cellulosic fuels. The historic availability of cellulosic biofuel waiver credits has created an alternative to purchasing D3 RINs. Because of the hesitance of the market to accept the D3 RINs during the initial emergence of cellulosic fuels, RIN integrity standards seem paramount to the value and marketability of these RINs.

Several companies provide quality assurance plan (QAP) services for RINs and many already have a risk management plan in place with the EPA for QAP of cellulosic ethanol RINs. The key components of the plan are to differentiate the feedstocks and processes used for cellulosic ethanol and to monitor the quantities of feedstock used and the quantities of cellulosic ethanol produced. These quantities are then compared to the yield tolerances of a particular facility’s process and footprint. 

The QAP program should, and must, have a way to differentiate the amount of ethanol produced from cellulosic feedstock and starch-based feedstock at an ethanol plant. In a program developed by Genscape Inc., devices monitor plant infrastructure such as pumps and other equipment to differentiate types of processes. Also, monitoring of volumes of reagents used may be required to further validate the process. To make sure the fuel leaves the facility, the QAP includes transportation monitoring as well. Using technologies to monitor plant infrastructure reduces the need for onsite verification visits, and third-party confirmations are performed to assure downstream contracts for the fuel.

To help the producer, a QAP provider can act as an RFS2 partner. The QAP provider helps make sure the correct reporting, recordkeeping and registration components are in place and that RIN generation practices are valid. Several QAP providers also have services to help streamline the registration process for facilities that want to incorporate a pathway for cellulosic fuels. 

The EPA has also proposed in its “Pathways II” rule published in June 2013 that corn kernel fiber be considered crop residue, which is already an accepted feedstock category for cellulosic ethanol. On a side note, the proposed rule also indicates that corn stover would also qualify as crop residue for cellulosic ethanol production, clearing the stage for more cellulosic ethanol from the corn plant.

Currently operating dry-grind ethanol plants hold the key to large-volume cellulosic ethanol production using corn kernel fiber-to-ethanol conversion technologies. While the technology is readying commercialization, the industry must ensure that RIN integrity standards support the marketability of D3 cellulosic RINS. This, too, can be achieved using monitoring technologies that reduce the need for onsite verification visits.

Author: Steffen Mueller, PhD 
University of Illinois at Chicago, 
Energy Resources Center and 
Genscape Inc. 
[email protected]

Contributors: Sabrina Trupia, PhD, NCER
CSusan Olson, PhD, Genscape Inc.