45Z Guidance: An Agronomist's Guide to Feedstock CI Scoring
The long-awaited USDA technical guidelines and updated Feedstock Carbon Intensity Calculator (FD-CIC) under the 45Z Clean Fuel Production Tax Credit have finally arrived, and the proposed preliminary guidelines are a significant sea-change for feedstock producers in a biofuel supply chain. For affected farmers and ethanol plants, these updates present both opportunities and challenges, with a clear emphasis on rewarding conservation-focused farming practices without the ultra-granular scoring complexities of the previous frameworks.
Our team of agronomists, farm-kids, and ag-professionals have been hard at work pouring over these recently released guidelines to give you a boots-in-the-dirt 45Z analysis highlighting what feedstock suppliers need to know in 2025. Join us as we review an agronomist’s guide to feedstock CI.
A Simpler Path to CI
The new 45Z feedstock scoring guidance lowers the barrier for entry for farmers by simplifying the carbon intensity (CI) scoring process. Instead of a detailed, granular score, the focus has shifted to more towards unbundled practice verification. This means that farmers can be directly rewarded for how they farm rather than getting lost in the intricacies of an-ultra granular input/output point-based system.
The new USDA FD-CIC is the primary tool for calculating the CI of feedstocks used in biofuel production. It builds on the GREET model but incorporates new methodologies for assessing the carbon impact of agricultural practices. The big shift? A greater emphasis on declaration of practices, capture of on-farm data and documentation, all without the downside of penalties for inefficient feedstock production.
Farmers who can document conservation-focused management practices will see an advantage, but those relying on default values will be assigned a national-average score, which may not reflect the true CI reductions they’ve achieved.
NOTE on Regional Impacts: The simplicity of 45Z benefits some regions more than others. Areas with established conservation practices may find this an easy transition, while those needing more adaptation could face hurdles. Remember that the GREET Model and FD-CIC is constantly evolving and thus, never “perfected”. You’ll find that certain regions can more easily accommodate and implement the current conservation practices outlined in 45Z. Don't see a valuable conservation management practice in the new guidance? Let USDA know directly by March 15
Tillage Practices: Know Your STIR Values
One of the standout clarifications in the guidance is around Soil Tillage Intensity Rating (STIR) values. These values set the bar for what qualifies as reduced tillage or no-till under the USDA guidelines and have thresholds which have slightly changed from previous guidelines.
- Reduced Tillage:
Permits disturbance methods like chisel plowing and field cultivating, provided the STIR value does not exceed 80. - No-Till:
Strictly prohibits full-width soil disturbance, with a stringent STIR value limit of 20. Practices like strip tillage and fertilizer injection are allowed, but burning residues is not.
Most growers may find their STIR values higher than expected, making this an essential metric to verify before planting. Producers who participated in previous CI programs may see a change in their tillage classifications.
The Power of Combined Practices
1 + 1 ≠ 2
The updated 45Z FDCIC confirms that, in most cases, combining CSA practices can lead to a lower CI score than implementing practices individually. This is a critical insight for growers strategizing to maximize their credits. (Table below utilizing management and SOC modeling from Whiteside County, IL)
A new element multiplying these combined practices is perhaps the most consequential change in the new FDIC and the USDA’s updated procedure for recognizing soil organic carbon (SOC). Previous iterations of CI scoring frameworks suggested that county-specific SOC modeling could drive differentiation in scores (and leave other regions without any SOC credit at all). Instead, the latest guidance has expanded SOC modeling across all corn ground counties, expanding the opportunity for farmers in all regions to recognize on-farm carbon sequestration potential
Cover Crops: The Biggest Lever with the Biggest Risk
Cover crops remain the single biggest lever to reduce feedstock CI under the USDA’s 45Z guidance, offering significant benefits for both soil health and conservation plus carbon intensity scoring. However, they come with strict limitations—cover crops cannot be paired with the “spring-only”, and they must align with reduced tillage or no-till practices to fully realize CI benefits. When combined with no-till, cover crops can push CI scores to some of the lowest achievable levels, but the management complexity increases significantly and regional limitations remain on practical feasibility of implementation.
Nitrogen Management: Nuances to Navigate
Nitrogen (N) application timing and the use of nitrification inhibitors are pivotal to achieving favorable CI scores. The guidance provides a clear path but also highlights some model limitations:
- The optimal N management approach is spring-only N with a nitrification inhibitor.
- To qualify, 100% of your N must use a nitrification inhibitor, and 75%+ of N must be applied post-crop emergence to qualify for “split in season.”
- There are notable model failures, such as the inability to qualify for both “split in season” and “n inhibitor” simultaneously.
- Additionally, cover crops cannot be combined with the “spring only fertilizer” strategy.
The Compliance Burden: What Growers Need to Prepare For
With greater emphasis on practice vs granularity in CI scoring comes a new challenge: verification. Often on practices that have little to no recorded data, like tillage, declaration and attestation are the most feasible solution for verifying practices. The USDA’s framework emphasizes this attestation and independent verification, but note that details may change whenever guidance is finalized.
For growers, this means:
1. Data collection is non-negotiable:
Farmers looking to recognize lower than default CI scores must diligently document nitrogen use, tillage practices, cover cropping, and other key factors plus retain critical support documentation.
2. The bar for verification is rising:
Third-party audits will be required for a subset of participants and independent verification will be required for all participating farm operations.
3. Mass balance tracking:
The ability to accurately track production from the field to your physical delivery point (known in the guidance as your First Point of Aggregation) will be critical for program compliance.
This shift underscores a broader reality: the 45Z credit will dramatically favor growers who can prove their data accuracy and subsequent emissions reductions, not just those who claim them.
Conclusion: A Word from the Field
As an agronomist and CI scoring professional, I see firsthand how diverse farming operations are across the country. What works in the plains of Iowa might not translate to the drylands of Kansas or the humid fields of the Southeast. The new 45Z guidance provides a roadmap, but each farm needs a custom approach. I encourage growers to reach out to their local agronomist to tailor management decisions that maximize both CI scoring and agronomic success. At Incite.ag, we’re here to help biofuel stakeholders navigate this complex landscape with practical, on-the-ground support.
Riley Harbaugh, CCA
General Manager, incite.ag
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Incite.ag guides producers across the agricultural supply chain to Turn Emissions into Income. Incite.ag’s CI scoring system unlocks novel revenue streams and empowers producers to take control of their unique CI Scores. Learn more by hitting the link below or reach out to the team directly at success@incite.ag or 815.373.0177.
