The biofuels industry is sparking more interest in carbon intensity (CI) scores, not only for ethanol plants, but also with corn farmers who produce feedstocks for ethanol. However, there is some uncertainty on how to calculate CI scores, how they can be used and what factors go into calculating scores.
Iowa Corn created this grower guide to help farmers understand CI scores and to provide guidance on what to ask companies that offer CI calculations. This area is evolving rapidly, so the information in this guide is up to date through August 2024.
Inputs and practices that drive the FD-CIC
The Feedstock Carbon Intensity Calculator (FC-CIC) is a free tool used to calculate corn grain CI scores using farm data and farm management practices. For farmers, the CI score is based on agronomic inputs and management practices and constitutes what is known as the cradle to farm-gate stage.
The left side of Figure 1 illustrates the inputs for the feedstock (i.e., corn) production portion of the system. It includes energy and raw materials used to produce the inputs and on-farm energy consumed to produce the corn crop. The right side of Figure 1 shows the steps, inputs and emissions once the grain arrives at an ethanol plant.
1: The system boundary of FD-CIC (i.e., cradle to farm-gate activities) compared to a complete supply chain of a biofuel (modified from Liu et.al., 2021), Argonne National Laboratory.
Figure
DISCOVERING YOUR CI SCORE
Tables 1 and 2 identify inputs and practices used in the FD-CIC to calculate a CI score in a corn-following-soybean rotation. The values in Table 1 are default national averages and are used as reference points. The national average CI score for corn is 29.1; CI scores for Iowa are in the 25 to 28 range depending on the county. The national average yield is 175 bushels per acre; the average yield for Iowa has been in the 200 bushels per acre range. Higher yields typically lead to lower CI scores because the energy used and emissions produced are spread across more bushels. The FD-CIC allows for the entry of actual values so a farmer can calculate their CI score on a field or farm basis using data from their farm.
Farm Inputs: Corn Following Soybeans
2.1.1)
Table 2 lists several practices that have discrete rather than numeric inputs.
The FD-CIC asks the user to enter information about their operation. If no-till, cover crops and/or manure applications are entered, the soil organic carbon value is automatically included in the calculation. Once all the selections are made, the user clicks the Calculate button and the results are displayed.
Management Practice Input
or No Manure Yes or No
Nitrogen Management Base Case, Enhanced Nitrogen, 4Rs**
Source of Nitrogen Conventional Ammonia, Green Ammonia
Table 2. Management practice inputs for the Feedstock Carbon Intensity Calculator (FD-CIC).
* C = Corn, SB = Soybeans
** Refer to fertilizer applications by using the right source, rate, time and place.
Table 1. Crop inputs for the Feedstock Carbon Intensity Calculator (FD-CIC).
LOWERING THE CORN CI SCORE ON YOUR FARM
The FD-CIC is a useful tool for running scenarios to see how practice changes impact the score. For example, if you are currently using reduced tillage and are curious to see how no-till affects your score, you can change tillage types in the tool and recalculate the CI score.
Carbon Intensity Scores for Farmers
For corn farmers, carbon intensity is the production footprint assigned to a bushel of grain. The score is generated using the federally approved computer model (called GREET) and its associated tool known as the Feedstock Carbon Intensity Calculator (FDCIC). There are numerous practices farmers can adopt to reduce their score.
Soil Organic Carbon
Calculating Carbon Intensity Scores for Farmers
National default inputs used for farm practices in Story County, Iowa, with a 192 bushel per acre yield, used as reference for SOC change. Baseline land management is reduced-till, no cover crop, no manure and business as usual N management.
“The Works” includes no-till, cover crops, green NH3, 4R nitrogen and manure.
As shown in the table, it is possible to achieve a negative CI score by no-till, planting a cover crop, using green ammonia and the 4Rs of nutrient management, and applying manure (“The Works”). This combination of practices reduces the baseline CI score by nearly 31.0 points, resulting in a CI score of -5.2.
KEY CI SCORE TERMS:
GREET Model
The GREET ® ( G reenhouse G ases, R egulated E missions, and E nergy use in T echnologies) model was first published in 1995 by Argonne National Laboratory with the support of the U.S. Department of Energy (DOE) and is updated annually. GREET is a life cycle analysis (LCA) tool used to systematically examine the energy and environmental effects of a wide variety of transportation fuels and vehicle technologies in major transportation sectors.
Carbon Intensity Scores for Fuels
Fuels are scored based on the amount of CO2 or greenhouse gas emissions associated with a megajoule of energy. The carbon intensity of ethanol is determined with the life cycle analysis (LCA) technique, which accounts for the energy/material uses and emissions during the complete supply chain of biofuel, including feedstock (i.e., corn) production, fuel conversion processes and ethanol delivery.
Corn production can be managed to enhance soil organic carbon (SOC) sequestration with conservation farming practices by increasing carbon inputs to soils (via crop residues) and/ or reducing carbon losses from soils. FDCIC accounts for the potential SOC changes associated with changes in farming practices. The baseline practice is set as a two-year rotation of corn and soybeans with reduced tillage. Once users select the farm location, crop rotation and land management practices, such as tillage, cover crops and manure, the corresponding SOC change results are displayed. (Source: Feedstock Carbon Intensity Calculator [FD-CIC] Users’ Manual and Technical Documentation. Xinyu Liu, Hao Cai, Hoyoung Kwon and Michael Wang. October 2023.)
Farmers are interested in knowing their CI scores for several reasons. Some have heard about CI scores and are curious what their score is, based on their current agronomic inputs and management practices (i.e., tillage). Others want to see how their CI score changes if they add or subtract a practice or increase or decrease an input. Still, others may want to know their CI score because they want to take advantage of markets paying premiums for low-CI corn.
Carbon Intensity Calculators
CI score calculators may have different features and input pages, but most, if not all, are running the FD-CIC behind the scenes. This is because the FD-CIC is authorized by the U.S. Department of Energy (DOE) and is the tool that is generally accepted as the gold standard for calculating CI scores at the farm level.
When using an FD-CIC calculator, make sure you are using the most recent version. The FD-CIC is a component of the GREET model that is updated annually. The FD-CIC is a free, publicly available tool that requires relatively few inputs from a farmer.
is a unit of work or energy and equivalent to the energy to light a 100-watt light bulb for three hours.
Table 3. Management Practices that Impact Corn CI Scores (Story County, Iowa).
45Z TAX CREDIT
Section 45Z of the Inflation Reduction Act (IRA) provides a tax credit for the domestic production of clean transportation fuels, including ethanol, biodiesel and sustainable aviation fuels. It applies to fuels produced after January 1, 2025, and sold before December 31, 2027. For ethanol plants, the 45Z credit is available to facilities that achieve a CI score below 50 and pays 2 cents per gallon for every CI point below 50. For example, if a 100 million gallon ethanol plant has a CI score of 40, they could receive $20 million in tax credits. The formula is (10 CI points x $0.02 per gallon) x 100 million gallons.
40B TAX CREDIT
The 40B tax credit incentivizes the production of sustainable aviation fuel (SAF) that achieves a life cycle greenhouse gas emissions reduction of at least 50% as compared with petroleum-based jet fuel. The tax credit encourages the use of certain climate-smart agriculture (CSA) practices for SAF feedstocks, including the combination of no-till, cover crops and enhanced-efficiency fertilizer. 40B guidance was not released until April 2024, so very few, if any, entities qualified for the 40B tax credit. The 40B tax credit expires December 31, 2024.
Q&A FOR CARBON INTENSITY SCORES
Should I pay a company to calculate my CI score?
Several companies advertise their ability to calculate CI scores; some charge a fee while others do not. Most, if not all, of these companies use the FD-CIC, which is the farm input calculator embedded in the GREET model. The decision to work with a company to get your CI score is up to each farmer. It is suggested that farmers get their CI score from more than one company to see how they compare. The scores should be very similar if both companies are using the FD-CIC. If they are different, ask each company about their calculations. You may also want to check with these companies to see if they offer services beyond generating a CI score.
How can I monetize my commitment to these improved practices if I don’t deliver corn to an ethanol plant?
Although you would not currently qualify for a share of 45Z tax credits if you do not deliver corn to an ethanol plant, there may be other opportunities where you could qualify for a payment or premium. These include carbon credit programs or grain buyers who have a low-CI corn program.
How do I know if an ethanol plant will share 45Z tax credits if I deliver low-CI corn to them?
Ethanol plants receiving 45Z tax credits will determine if and how they reward farmers for lower-CI grain. Farmers should be in close communication with their ethanol plant to understand how any tax credits will be shared. Tax credit revenue sharing will be market driven, not influenced or decided by a government agency.
Can an ethanol plant lower their CI score without purchasing low-CI corn?
Yes, an ethanol plant can lower their CI score without purchasing low-CI corn. If an ethanol plant is connected to a carbon capture and storage pipeline, reduces the energy consumption of their operations, and/or implements other practices that reduce carbon emissions to achieve a CI score under 50, they can qualify for the 45Z tax credit.
How do the 45Z tax credits differ from payments from a voluntary carbon market program?
The 45Z tax credits are based on the CI score of an ethanol plant. To receive the credit, plants must have a CI score below 50. Farmers can contribute to lowering a plant’s CI score by delivering low-CI corn to the plant. Farmers with low-CI corn need to communicate with the ethanol company to understand if and how the plant will compensate farmers for the grain.
Voluntary carbon market program payments are made directly to farmers if they meet the program requirements. Often this means the farmer must make an improvement in a practice to receive compensation, such as converting acres from conventional-till to no-till or planting cover crops in a field for the first time. Converting to new climate-smart practices is known as additionality and pays farmers to implement these new practices; however, it usually excludes farmers who have used improved practices previously — in many cases, for years or decades.
How will CI scores and the 45Z tax credit impact livestock producers?
45Z tax credits only apply to the fuel produced by the plant and are only available to the plant if their CI score is below 50. In the future, there may be market opportunities for low-CI scores for livestock. There is also the possibility of a “book and claim” system. This might allow a farmer who produces low-CI corn to receive a certificate that is separated from the physical grain that an ethanol plant can purchase and compensate the farmer with a payment. Book and claim and mass balance programs are still in development, with no guarantee either of them will be implemented.
How can I access the CI score calculator developed by Iowa State University?
Iowa State University (ISU) developed a free CI calculator that went live with instructions on the ISU Ag Decision Maker webpage on July 15, 2024. Scan the QR code to access the calculator.
There is a lot of buzz and uncertainty about carbon intensity scores, how they are calculated, and their impact on farmers and ethanol plants.
The Iowa Corn Promotion Board developed this grower guide to define and describe some of the key aspects of CI scores and provide answers to frequently asked questions. Updates will be provided when more information becomes available.
iowacorn.org/join Scan this QR code to take you to the membership page.
