Monthly Average Ethanol Yield: Clarification Note
By Sampath Jayasinghe and David Miller
Decision Innovation Solutions, 11107 Aurora Avenue, Urbandale, IA 50322.
Iowa Farm Bureau Federation, 5400, University Avenue, West Des Moines, IA 50266.
January 31, 2017
In AgMRC’s January 2017 article, we looked briefly at the national average ethanol yield from October 2014 to October 2016. We took the monthly corn consumption data on fuel ethanol production from the USDA-NASS, and also used monthly fuel ethanol production data from USDA-ERS. That simple calculation indicated the national average ethanol yield set a record high of 3.0 gallons per bushel of corn crush in March 2016.
According to some constructive feedback from the scientific community, it’s difficult to believe 3.0 gallons of ethanol per bushel of corn is possible. Chemically, that level would require significantly higher starch corn than currently produced. Yet it’s puzzling to see ethanol yield numbers close to 3.0 gallons per bushel of corn from March 2016 to June 2016. That four-month period shows a distinct pattern of deviations from the time trend line (See Figure 7 in January 2017 report). The purpose of this article is to delve into some interesting data issues in our January 2017 report, and provide reasonable national ethanol yield estimates based on publicly available data.
First, we looked at the ethanol production data from USDA-ERS, which is based on the Energy Information Administration’s (EIA) Fuel Ethanol Supply and Disposition report. EIA’s Monthly Oxygenate Report (EIA-819) is used to collect data on plant production of fuel ethanol. According to EIA-819 Monthly Oxygenate Report Instruction, it is mandatory, by law, and must be completed by the operators of all facilities that produce fuel ethanol as part of their operations in the United States. The production data include both the production of denatured fuel ethanol (Code 190) and undenatured fuel ethanol (Code 191). The reporting of undenatured fuel ethanol production is required only when it is produced as a finished product intended for shipment. This report excludes any ethanol production intended for beverage, industrial, or other nonfuel use.
EIA does not publish undenatured fuel ethanol production separately. According to private communication with EIA staff, it represents a small portion, typically less than 10 percent, of total fuel ethanol production reported to EIA. In that case, we assume EIA’s ethanol production data typically contains 5 percent denaturant, and that more than 90 percent of reported ethanol is typically denatured. This educated guess leads us to calculate a conservative estimate of national ethanol yield. Table 1 shows ethanol production data adjusted for denaturant from October 2014 to October 2016.
Table 1: Monthly Average Ethanol Yield per Bushel of Corn/Sorghum (Oct. 2014-Oct. 2016)
EIA’s ethanol production data covers ethanol produced commercially from mainly corn starch, plus many other feedstocks such as sorghum, corn fiber, and waste products. We don’t find public data on fuel ethanol production based on different feedstocks. The Grain Crushing and Co-Products Production report published by the USDA-NASS separates corn and sorghum crush for fuel ethanol production. However, a clear and consistent monthly breakdown of sorghum crush for dry mill ethanol production is not available for 2015 because, as in most cases, the USDA-NASS withheld that information to avoid disclosing data for individual operations. Total dry mill sorghum crush in 2016 is estimated at 135.6 million bushels compared to 35.8 million bushels in 2015.
Total monthly corn and sorghum consumed for fuel ethanol is shown in Table 1. The estimated monthly average ethanol yields using total monthly corn and sorghum crush and ethanol production data adjusted for denaturant from October 2014 to October 2016 are shown in the last column in Table 1. The average ethanol yield for the first 10 months in 2016 stands at 2.70 gallons per bushel, compared to 2.68 gallons per bushel for the same period in 2015.
Mueller (2016) provides the most current, peer-reviewed literature published since 2010 on efficiency gains in corn-to-ethanol processing, including corn ethanol yields. Mueller reports the undenatured ethanol yield of 2.82 gallons per bushel based on a comprehensive industrial survey conducted in 2012. Also, he reports results on two previous industrial surveys conducted in 2001 and 2008. The undenatured ethanol yield in 2008 was at 2.78 compared to 2.64 in 2001. Results of the above three surveys of the ethanol industry shows a clear, positive trend in efficiency gains on corn-to-ethanol processing.
The relatively low values of ethanol yield in this analysis compared to Mueller’s numbers are due to various limitations in publicly available data. The ethanol production data from EIA accounts for all commercial ethanol, not just ethanol made only from corn starch. We only know corn and sorghum crush for fuel ethanol, and the data on other feedstocks usage is not available. The assumption of 5 percent denaturant in EIA’s ethanol production data is a very conservative guess. The use of denaturant can vary by plant and there is no simple way to adjust it. We also suspect denaturant is not the only influence here. Here we tried to address the question raised in our January 2017 report - what explains the upward blip in ethanol yields from March to June last year? It is important to note here that it could be measurement error associated with the ethanol production survey or the crush survey, or both. We want to end this discussion with a note that appears at the end of The Grain Crushing and Co-Products Production report from USDA-NASS.
“Reliability: Approximately 130 reports are received each month, which represent about 90 percent of total capacity. Monthly data can vary due to different firms reporting month-to-month. Survey data are also subject to non-sampling errors such as omissions and mistakes in reporting and in processing the data. While these errors cannot be measured directly, they are minimized by carefully reviewing all reported data for consistency and reasonableness.” Page 3, Grain Crushing and Co-Products Production, USDA-NASS.
U.S. Energy Information Administration (EIA), 2016. Fuel Ethanol Supply and Disposition. Downloaded December 30, 2016.
USDA-NASS (U.S. Department of Agriculture, National Agricultural Statistics Service), 2017. The Grain Crushing and Co-Products Production. Downloaded February 2, 2017.
Mueller, Steffen. “Request for Correction of Information: Concerning the U.S. Environmental Protection Agency’s Lifecycle Analysis of Ethanol and Gasoline Under the Renewable Fuel Standard,” April 11, 2016
We thank Dr. Charles R. Hurburgh, Dr. Scott H. Irwin, and Dr. Steffen Mueller for helpful discussion on this topic