Guidance on Qualifying an Analytical Method for Determining the Cellulosic Converted Fraction of Corn Kernel Fiber Co-Processed with Starch

(Environmental Protection Agency) This document provides updated guidance on qualifying an analytical method for determining the cellulosic converted fraction of corn kernel fiber co-processed with starch in order to demonstrate compliance with the regulatory requirements in 40 CFR 80.1450(b)(1)(xiii)(B)(3). 1

Public confidence in the volumes of cellulosic ethanol produced under the Renewable Fuel Standard (RFS) program is important to the integrity of the program. As such, affected stakeholders sought clarification from the EPA regarding what methods should be used to determine the cellulosic converted fraction of corn kernel fiber in the production of cellulosic ethanol.

EPA first issued guidance on this topic in May 2019.2 As the state of science has continued to evolve in this area, we are now updating our previous guidance. This document supplements the May 2019 guidance on qualifying an analytical method for determining the cellulosic converted fraction of corn kernel fiber co-processed with starch.

The intent of this guidance is to explain our interpretation of the regulatory requirements and to articulate clear criteria for the types of analysis and demonstrations that EPA believes can be accepted for registration under the program. This updated guidance reflects recent work conducted by the Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) 3,4 to develop a public method which addresses the analytical concerns identified in the 2019 guidance and includes consideration of recently released reference materials by the National Institute of Standards and Technology (NIST).5,6

Based on the availability of the NREL method for determining the cellulosic converted fraction of corn kernel fiber co-processed with starch at a traditional ethanol facility and the availability of NIST reference materials, this guidance describes three potential ways companies might satisfy the registration requirements:

1. Adoption of the DOE/NREL method,
2. Demonstration of reasonable accuracy by returning comparable cellulose values to the NIST reference materials using a non-voluntary consensus standards body (non-VCSB) method, or
3. Use of advanced analytical techniques; e.g. mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR), as identified by DOE/NREL in their analytical method and validation.

Our rationale for accepting NREL’s method, as well as for the additional options based on NREL’s method, for renewable fuel production facilities to use in demonstrating that they can measure cellulose with reasonable accuracy are discussed in this updated document.

EPA evaluates registration applications on a case-by-case basis given the best available information and science relating to analytical methods for determining the cellulosic converted fraction of corn kernel fiber co-processed with corn starch. This guidance elaborates upon EPA’s current view on the manner in which facilities can demonstrate the accuracy of such analytical methods and thus satisfy the applicable registration requirements. However, it is not an exclusive list of ways in which facilities may satisfy those requirements and any decisions on individual facilities’ registration applications will be made in the context of each of those applications on the basis of the requirements of EPA’s regulations. This guidance does not create any new requirements and may not apply to a particular situation based on the circumstances.

This guidance is organized into the following topics: (1) background and explanation of the relevant regulations; (2) background and overview of the 2019 guidance; (3) updates in the current guidance based on new science; (4) VCSB methods; and (5) a summary of EPA’s current guidance.

1 Requiring renewable fuel producers seeking to generate D-code 3 or 7 RINs who intend to produce a single type of fuel using two or more feedstocks converted simultaneously, where at least one of the feedstocks does not have a minimum 75% average adjusted cellulosic content to provide, inter alia, “[c]hemical analysis data supporting the calculated cellulosic Converted Fraction and a discussion of the possible variability that could be expected between reporting periods per § 80.1451(b)(1)(ii)(U)(1). Data used to calculate the cellulosic CF must be representative and obtained using an analytical method certified by a voluntary consensus standards body, or using a method that would produce reasonably accurate results as demonstrated through peer reviewed references provided to the third party engineer performing the engineering review at registration.”

2 Environmental Protection Agency Guidance on Qualifying an Analytical Method for Determining the Cellulosic Converted Fraction of Corn Kernel Fiber Co-Processed with Starch, EPA-420-B-19-022. May 2019.

3 Michel, Katie, Justin Sluiter, Courtney Payne, Ryan Ness, Brittany Thornton, Michelle Reed, Alexa Schwartz, and Ed Wolfrum. 2021. Determination of Cellulosic Glucan Content in Starch Containing Feedstocks. Laboratory Analytical Procedure (LAP), Issue Date: February 26, 2021. Golden, CO: National Renewable Energy Laboratory. NREL/TP-2800-76724. https://www.nrel.gov/docs/fy21osti/76724.pdf.

4 Michel, Katie, Justin Sluiter, Courtney Payne, Ryan Ness, Brittany Thornton, Michelle Reed, Alexa Schwartz, and Ed Wolfrum (2021) Direct Determination of Cellulosic Glucan Content in Starch Containing Samples. Cellulose 28:1989-2002. https://doi.org/10.1007/s10570-020-03652-2.

5 National Institute of Standards and Technology Reference Material 8644. Dried Corn Biomass Intermediate Before Conversion. June 23, 2021.

6 National Institute of Standards and Technology Reference Material 8645. Dried Corn Biomass Intermediate After
Conversion. June 23, 2021. READ MORE

Excerpt from Growth Energy: Yesterday, the U.S. Environmental Protection Agency (EPA) released its updated guidance on what methods should be used to determine the cellulosic converted fraction of corn kernel fiber in the production of cellulosic ethanol. Growth Energy CEO Emily Skor released the following statement in response:

“We’re pleased to see EPA update its guidance for cellulosic biofuel from kernel fiber, a move that provides additional flexibility for bioethanol producers and the potential to accelerate stalled registrations for cellulosic biofuels. Approval of these registrations is important to fulfilling the goals of the Renewable Fuel Standard and to help further decarbonize the transportation sector. We look forward to further reviewing EPA’s guidance with our members.” READ MORE