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45Z Carbon Intensity Calculator

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ACE created this carbon intensity (CI) calculator to help ethanol producers and farmers estimate the maximum potential value of the Internal Revenue Code §45Z Clean Fuel Production Tax Credit based on real-world farm practices and process technologies which impact the lifecycle greenhouse gas (GHG) emissions of corn ethanol.

Under §45Z of the tax code, beginning January 1, 2025, transportation fuel with a published emissions rate of 50 kilograms of CO2e/mmBtu or less can qualify for a base credit of $0.20 per gallon for non-aviation fuel ($0.35 per gallon base credit for aviation fuel), and up to $1.00 (and $1.75 respectively) if wage and apprenticeship requirements are met. The 45Z tax credit only applies to transportation fuel sold and used by December 31, 2027, unless extended by Congress.

How to Use the Calculator

Our calculator’s emission rates are based on the Department of Energy GREET model, which the law requires Treasury to use to publish emission rates under 45Z.

  • The blue column of the calculator includes every input used to calculate ethanol’s carbon intensity score based on the GREET model.

  • The brown columns of the calculator show the GREET model default values for each of those inputs.

  • The green columns of the calculator enable users to enter their own data in the yellow boxes and calculate a unique emission rate/CI score based on the GREET model. The yellow boxes are pre-populated with GREET default values. Use the tab key to toggle to-and-from yellow boxes.

The final columns of the calculator enable users to compare their unique results to GREET default values and view the economic value expressed in dollars per gallon or dollars per acre.

The grand total box at the bottom of the calculator contains the final user-specified CI score/emissions rate and overall change compared to the GREET default. It also shows the total economic benefit. Users are given the option to email the results to themselves and ACE.

The top of the calculator shows easy-reference bar charts summarizing and comparing GREET default and user-specified corn ethanol carbon intensity scores, highlighting key factors used to determine emission rates.

Access the Calculator

Important Disclaimers

Because carbon intensity market value is typically expressed in dollars per ton, our calculator sets the value of 45Z to a carbon credit price of $262 per ton, the maximum potential credit which can be claimed for non-aviation fuel only if the wage and apprenticeship requirements are met. The 45Z tax credit is transferable, so as a market to connect tax-credit buyers and sellers evolves, credits may sell at less than face value. While ACE is urging Treasury to allow all the farm-level practices in our calculator to qualify toward corn ethanol emission rates, there is no guarantee Treasury will allow this and virtually no guidance on how 45Z will be implemented at this time.

The information provided by our calculator is offered as a public service. This calculator/website is not to be interpreted as furnishing any personal, legal, or tax advice to taxpayers. In no event shall ACE be liable for any loss, expense, or other adverse effect caused by reliance on any information derived from the calculator or appearing on this website.