Understanding Carbon Intensity (CI) Scores is relevant for anyone involved in the 45Z tax credit and the broader field of renewable fuels. CI Scores are necessary for evaluating the ecological impact of various fuels, guiding policy decisions, and helping industries meet decarbonization goals. This article explains what a CI Score is, how it is calculated, and why it matters.

What is a CI Score?

The CI Score measures how much carbon dioxide (CO2) is emitted per unit of energy or fuel. It is typically expressed in grams of CO2 equivalent per megajoule (gCO2e/MJ). According to Continuum Ag, conventional corn currently grown in the United States averages a CI Score of 29.1 kg CO2E/mmBtu, for example. The CI Score reflects the lifecycle emissions of a fuel, considering all stages from raw material extraction to the final use of the fuel. A lower CI Score indicates a smaller ecological impact, and, consequently, 45Z and programs like it seek to lower CI Scores in agriculture, aviation, logistics, and other fields relevant to biofuels.

How is a CI Score Calculated?

The calculation of a CI Score involves a comprehensive lifecycle analysis (LCA) of a fuel, often using the GREET Model. Without getting lost in the minutiae, here are the steps involved:

1. Feedstock Production: This includes the cultivation and harvesting of crops used as feedstocks, such as corn for ethanol or soybeans for biodiesel. Emissions from farming activities, fertilizer application, and land use changes are considered.
2. Feedstock Transportation: Emissions from transporting the raw feedstocks to processing facilities are included. This can involve various modes of transportation, such as trucks, trains, or ships.
3. Fuel Production: The processing of feedstocks into biofuels naturally generates emissions. For instance, the fermentation process in ethanol production or the transesterification process in biodiesel production contributes to the overall CI score by emitting CO2.
4. Fuel Transportation: After production, the transportation of biofuels to distribution centers or end-users also contributes to the CI score.
5. Combustion: Finally, the emissions produced when the fuel is burned in engines or other applications are included in the CI score. This accounts for the CO2 released during fuel use.

For the non-accountants reading, I bet you are glad you do not need to do this by hand! But all the stages are important. Each contributes to the total emissions associated with the fuel. The sum of these emissions is then divided by the total energy content of the fuel (think “how many miles could I drive with this blend?”) to determine the CI score.

Tools for Calculating CI Scores and the GREET Model

Luckily, as aforementioned, you need not do this by hand — or from scratch. Several tools and models are used to calculate CI Scores. The most widely recognized is the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Technologies) Model developed by Argonne National Laboratory. The GREET Model provides a detailed framework for evaluating the lifecycle emissions of various fuels and technologies, making it a cornerstone in calculating CI Scores for renewable fuels.

So what?

CI Scores are useful for several reasons:

• Policy and Regulation: Governments use CI Scores to set regulations and incentives for renewable fuels. The 45Z tax credit relies on CI Scores to determine eligibility and how much to pay out.
• Ecological Impact: CI Scores help quantify the environmental benefits of renewable fuels compared to fossil fuels. By promoting fuels with lower CI Scores, policymakers can reduce nationwide greenhouse gas emissions.
• Industry Standards: CI Scores provide a benchmark for the biofuel industry to strive for lower emissions and more sustainable practices – saving money in the short term by eliminating costly externalities and in the long term by preserving a better, more arable world. Producers can use CI Scores to improve their processes and reduce their environmental footprint.

Conclusion

Being aware of and using CI Scores effectively is important for advancing sustainability that awards farmers and agricultural industries. By measuring and comparing the lifecycle emissions of various fuels, CI Scores help guide wise policy, improve industry standards, and ultimately reduce the environmental impact of energy production and consumption. As the 45Z program and other sustainability efforts continue to evolve, CI Scores will remain an invaluable tool in the pursuit of cleaner, greener energy.