Measuring Up Corn Fiber Ethanol

Ethanol made from corn fiber has a low carbon intensity and the potential to generate D3 RINs, but navigating the regulatory landscape to capture its fullest value can be complex.
By Katie Schroeder | September 17, 2022

Producing corn fiber ethanol alongside standard, D6 RIN-generating corn starch ethanol gives producers an opportunity to produce more gallons at a lower carbon intensity (CI) score. The current production volume of D3 corn fiber ethanol produced in the U.S. is relatively small. In June 2022, there were 576,022 D3 RINs generated by cellulosic ethanol producers—and less than half that volume in July.

Corn fiber ethanol fits into the RFS under pathway K, which allows ethanol produced from cellulosic content to earn D3 RINs, so long as it meets certain qualifications. There are two principal ways to produce corn fiber ethanol. One method is to produce it in-situ, meaning that an enzyme or other technology is introduced to break down the corn fiber, producing cellulosic ethanol simultaneous to  corn starch ethanol, at same plant. Another way of producing corn fiber ethanol is through extraction of the fiber upstream, manufacturing  cellulosic ethanol separately on-site. 

Measurement of fiber and starch content is one key part of determining qualification for D3 RINs under the EPA’s guidelines for in-situ production facilities. Kristi Plack is the chief science officer at Bion, the parent company of Soliton, which uses proprietary analytics, or tests, to give producers the defensible, third-party production data they need to run their plant optimally. She says Soliton can also provide information necessary for in-situ corn fiber ethanol facilities to potentially qualify for D3 RINs.

Other processes for corn fiber ethanol production utilize a separate system and do not require the same testing procedure to acquire D3 RINs. This method of production is to colocate a system with a primary ethanol plant. The plant will feed the fiber into the system, allowing for measurement of the cellulosic ethanol at the end due to the separate process streams. Ace Ethanol LLC, a 58 MMgy corn ethanol plant in Stanley, Wisconsin, is currently operating such a technology—and successfully generating D3 RINs.

Mark Yancey, chief technology officer for D3MAX, the technology developer behind the Ace corn fiber ethanol plant, says the system’s separate production streams make it unique to other alternatives. “From the day we formed the company in 2015, it was our plan to have a process through which we would create the cellulosic ethanol separate from the starch ethanol, and that the two would never cross paths until we measured the amount of cellulosic ethanol produced,” he says.

All biofuel producers must fill out an application to qualify for RINs under the RFS. Yancey explains that the terminology can be confusing, as people commonly refer to a Part 80 application as “pathway approval,” when in reality, the pathway already exists. “But what they really need is a Part 80 application approval,” he says. “So, if you build a D3MAX plant or you implement an in-situ process, if you want to participate in the RFS program, you have to fill out a Part 80 application. And a Part 80 application tells EPA how the process works, and how you measure or calculate the amount of ethanol or other fuel produced. That application is then reviewed and either approved or denied, or they ask for more information.”

Although both in-situ and separate process stream methods can qualify for D3 RINs, many in-situ processors have not pursued, or stopped pursuing, D3 RIN registration, and have instead focused on sending their low-CI, cellulosic-infused D6 gallons to the California market.

“The industry knows what the EPA needs to approve Part 80 applications, which allow [plants] to generate D3 RINs, but nobody has done that, and it’s been almost three years now [since the agency issued guidance on its treatment of in-situ processes],” Yancey says. “The other thing is that California, CARB and the Low Carbon Fuel Standard do allow in-situ processes to generate LCFS grants if they ship the ethanol—that cellulosic ethanol—to California.”

Measurement Regulations
Plack explains that the EPA’s regulations specify the qualifications that testing methods must meet in order to be used for calculating RINS; the two different types of testing are VCSB and non-VCSB methods. “VCSB, which is Voluntary Consensus Standard Body, is a method that’s been evaluated by a scientific organization that has its own internal method validation criteria,” Plack explains. “So, that would be like an ASTM, AOAC, AOCS, and those methods are then available for any laboratory in the world to use. If it’s not VCSB, it’s more of a proprietary-type assay and based on a … scientific peer-review process of the method utilized; meaning other scientists review the method, the application of the method and validate the method in the same manner, yet maintaining the confidentiality of the method.”

Plack says that producers must have starch and cellulosic content values at the beginning and end of the ethanol conversion process. “They need those results … to enter into the calculator—that is specified in the RFS—so they can get their D3 RIN value;  that’s why they need the test results, so that they have analytical values to show how much starch and cellulosic content they’re converting,” says TaNeal Boer, technical science director with Soliton.

The in-situ producers must test every 500,000 gallons of cellulosic ethanol produced, or annually, if they are not producing that volume of corn fiber ethanol. This is necessary due to the fact that the precise amount of fiber versus starch varies depending on the crop. “Corn may be misunderstood; corn is not just corn,” Plac,k says. “And when you’re looking at it from this type of process, every growing year has different things. So, Mother Nature, this year might be super hot and dry, and last year was colder and wet, so that changes how the corn develops, which changes the composition of that corn.”

While producers can go through tests to qualify for D3 RINs, there is no longer a clearly laid out pathway for corn fiber ethanol in-situ production through the EPA. “The industry knows that the EPA is not approving registrations currently,” Boer says. “In the interim, the industry has shifted focus to LCFS while the EPA is in a holding pattern. The facilities are doing the work to complete the Soliton analytical testing for a LCFS registration or an EPA registration. The Soliton testing regimen utilizes the same process, whether the facility is looking to submit a registration to CARB for their approval or prepare an application for EPA.”

Cellulosic content and starch are not the only testing information needed by CARB or the EPA to gain credits. There are also engineering reviews that look into the plant’s operation inputs and outputs, which are necessary to qualify for low-carbon fuel credits. “I think the important thing is that the measurement piece gives you the data, but the  engineering piece helps show that the operation matches the data that’s coming from that third-party laboratory,” Boer says. “Because they all need to go hand in hand, you can’t have data saying 'X' when a plant is doing 'Y.'”

CARB and D3 Markets
California is a leading market for low-carbon fuels like corn fiber ethanol due to the state’s LCFS and carbon reduction goals. Fuel with a lower CI makes more money in California, whether or not it has a D3 RIN attached to it, Yancey explains. “CARB requires applicants to prove the carbon intensity of their fuel. Then, that carbon intensity determines the value of that fuel,” he says. “It’s a [totally] different approach to EPA’s approach of assigning RINs, and the RINs having measured values.”

In order to get credit from the LCFS, producers must provide three months—90 days—worth of data to verify their carbon intensity score. CARB has been proactive in approving non-VCSB tests to allow producers to sell into the California market, according to Plack.

Producers utilizing separate process techniques, such as Ace Ethanol, are able to make money both in the California market and through D3 RINs. As of July 21, a D3 RIN was worth $2.74 per gallon. Yancey explains that a producer utilizing D3MAX will usually sell the D3 RINs to the highest bidder, and then buy a much cheaper D6 RIN, yielding a net gain of around $1.25 per gallon. After accounting for the sale price of ethanol in California and credit from the LCFS, the producer makes almost $4 per gallon.

Exploring D3 Production
Corn fiber ethanol provides producers with an opportunity to use cellulase or other technology, which may assist in the process of extracting more corn oil to gain more profit, Boer explains. “If they’re converting more fiber and extracting more oil, they could be decreasing their gas usage, which is decreasing their carbon footprint and also their cost,” she says. “Now, they’re producing and selling more ethanol gallons and corn oil; it’s a multifaceted benefit from the technology addition, whatever that is, to the process for those facilities.”

The D3MAX process has a separate distillation column for the corn fiber ethanol, and measures it using a mass flow meter that is accurate within 99 %, which the EPA uses to assign D3 RINs. The process doesn’t require recertification or measurement of cellulose and starch.

There are pros and cons to each process, Yancey explains. “The pros of D3MAX are, number one, that very high projected profit,” he says. “Highly profitable, quick payback. That being said, the con is that a large part of that is from RIN income and California LCFS credits. Those values go up and down, and are subject to political input and influence.”

D3MAX is also able to increase oil recovery from around 0.7 to 0.8 pounds per bushel to around 1.3 to 1.4 pounds per bushel. While an in-situ process produces 1 to 3 MMgy of cellulosic ethanol per 100 MMgy, the D3MAX process is able to produce about 8 MMgy in the same size plant. However, the higher yields of D3MAX come with a higher price tag, Yancey says. D3MAX costs around $25 million, while an in-situ process costs significantly less, while still increasing ethanol yields.

If a producer wants to incorporate a corn fiber ethanol process into their operations in an in-situ way, Plack recommends selecting an analytical testing provider that has experience in ethanol production, and has its testing approved by LCFS programs such as CARB, which has approved multiple different measurement options. She also suggests that producers discuss technology options with their enzyme vendor and other technology providers.

Although implementing corn fiber ethanol production is a complex investment, it has the potential to be an effective and beneficial addition to an ethanol plant’s portfolio.

“I think the ethanol industry really needs to take a look at corn fiber, whether it’s in-situ or separate processing like D3MAX, because it’s extremely profitable, and cellulosic gallons are going to become very, very in demand for making sustainable aviation fuel,” Yancey adds. “Ace has been approached several times [by potential buyers of] their cellulosic ethanol for various uses that match that low-carbon fuel. It’s one way for the ethanol industry to make cellulosic ethanol with a low CI right now, not in five or ten years—available today.”

Author: Katie Schroeder
Contact: [email protected]