I’ve written about and had an interest in corn fiber as a possible cellulosic feedstock for a while now. It started with stories about work at the National Corn-to-Ethanol Research Center and Quad County Corn Processors to ferment corn fiber into cellulosic ethanol. At the time, the unknown was whether the U.S. EPA would approve corn fiber as a feedstock for cellulosic ethanol.

Back in late May, the EPA came out with a proposed rule that, if approved, would define corn kernel fiber as crop residue. That would put corn fiber cellulosic ethanol in the same category as ethanol made from wheat straw, corn stover or sugarcane bagasse. This would allow corn fiber ethanol to qualify as an advanced biofuel and generate D3 renewable identification numbers (RINs). The 30-day comment period on this proposed rule, which includes other potential amendments to the renewable fuel standard, closes on July 15.

According to the proposed rule, the RFS2 definition of crop residue is biomass that is “left over from the harvesting or processing of planted crops” and has no “impact that would result in a significant increase in direct or indirect GHG (greenhouse gas) emissions.”  The proposed rule went on to clarify that it’s possible that some corn starch may still “adhere to the corn kernel after separation. The percentage of contamination will vary, but as much as 20 percent of the final fuel could be derived from corn starch.” The EPA then went on to point out that current regulations allow for feedstock contaminants that are impractical to remove or have to do with the common methods of feedstock production or transport. With this in mind, the EPA is specifically seeking comment on whether corn fiber should be defined as a cellulosic ethanol feedstock, considering the fact that corn starch ethanol has been excluded from qualifying as an advanced biofuel.

The topic came up at the International Fuel Ethanol Workshop & Expo, during the breakout session I wrote about in my blog last week. Scott Kohl, technical director of ICM Inc., talked about this in answer to a question from the audience. His opinion is that there’s more starch in corn than is currently fermented and he’s concerned that the definition of cellulosic ethanol from corn fiber needs to be carefully crafted in an intellectually honest way. Otherwise, it could damage the industry’s credibility. It could come out later that starch is being lumped into the fiber category and the accusation could be that it was all a ruse by the industry, as a way to convert starch into cellulosic ethanol and access advanced biofuel RINs—something critics may believe even if it’s not true.

Michael Regier, technical director of Cereal Process Technologies, agreed this was a potential problem. In a follow up email he told me this was a topic that definitely needed careful discussion. Commenting only on the issue of corn bran (or fiber) from milling, he said the starch contained would be minimal in comparison to the whole corn kernel. “Nonetheless it is there and should not be counted as cellulosic material even though it will end up contributing to biofuels production,” he said.

His opinion is that by using a simple proximate composition or through periodic testing already done in the milling step, the amount of starch and crude fiber can be measured using representative samples and weighing measures. That way, ethanol producers can account for the non-cellulosic gallons using existing and proven conversion rates. “In other words, if ‘starch’ gallons for a specific plant are produced at a demonstrated X gallon per pound of feedstock for that particular plant and ‘cellulosic’ gallons are demonstrated at Y gallons per pound of feedstock at the same plant, then proper accounting can be achieved,” he said, adding that if the concept were to be utilized it would need more definition.

As of today, there’s 21 days left to comment on the proposed rule. The time to talk about this, and come up with a solution, is now.