§45Q tax credit eligibility for AGI plants: A 2026 guide

Acid gas injection (AGI) plants can qualify for the §45Q carbon capture tax credit, but eligibility is not automatic—it depends on how the CO₂ is measured, what regulatory class the injection well falls under, and whether the operator satisfies EPA's Measurement, Reporting, and Verification (MRV) requirements under 40 CFR Part 98, Subpart RR. For a 2026 project evaluation, the key question is whether the injection qualifies as "secure geological storage" under the IRS definition—a different standard than the permitting standard for the injection well itself.

The short answer

AGI plants may qualify for §45Q if the CO₂ component of the acid gas stream is: (1) captured at an eligible facility, (2) injected into a formation that qualifies as geological storage under EPA Class II or Class VI well standards, and (3) measured and reported per EPA GHGRP Subpart RR.
The credit rate for qualifying geological storage is $85/tonne CO₂ if prevailing wage and apprenticeship requirements are met (base rate $17/tonne without PWA compliance).
The credit period is 12 years from the date the facility qualifies.
The minimum capture threshold is 1,000 metric tonnes CO₂/year for non-direct-air-capture facilities.
The distinction between acid gas disposal (no credit) and geological CO₂ storage (credit-eligible) is a legal and regulatory determination, not an engineering one alone.
Tax counsel with CCUS experience and a qualified MRV provider are required before claiming credits—this article is engineering context, not legal advice.

What §45Q is and where it stands in 2026

Section 45Q of the Internal Revenue Code (26 U.S.C. § 45Q) provides a per-tonne tax credit for carbon oxide captured from industrial facilities and either stored geologically or used in qualified enhanced oil recovery. The credit was originally enacted in 2008 and substantially revised by the Bipartisan Budget Act of 2018. The Inflation Reduction Act of 2022 (IRA) made three significant changes relevant to gas processing operators:

Increased credit rates — the geological storage credit increased to $85/tonne (PWA-compliant) from $50/tonne under the pre-IRA framework.
Extended the begin-construction deadline — eligible facilities must have begun construction by January 1, 2033 (extended from December 31, 2025 under the 2018 law).
Added the direct air capture (DAC) category at $180/tonne, which is not directly relevant to AGI plants but reflects the broader policy direction.

The statutory text (26 U.S.C. § 45Q) is available in full via eCFR and the IRS website. The IRS has issued guidance on §45Q through Revenue Ruling 2021-13 (addressing transfers of the credit), Notice 2020-12 (guidance on beginning of construction), and subsequent guidance on the IRA changes. Always verify against current IRS publications—this article reflects the law as understood in May 2026.

How AGI plants fit (and don't fit) the §45Q framework

Acid gas injection is a gas processing operation in which H₂S and CO₂ are removed from natural gas and injected into a deep formation rather than processed through a Claus unit for sulfur recovery. The economics typically favor AGI when the plant is remote, the gas volume is modest, or sulfur markets are weak.

The CO₂ in the acid gas stream is a genuine greenhouse gas emission source that is being diverted from the atmosphere into a geological formation. This sounds like exactly what §45Q was designed to incentivize. The complication is regulatory classification.

The UIC class matters. EPA's Underground Injection Control (UIC) program classifies injection wells. Most AGI wells are Class II wells (oil and gas-related injection). Class VI wells are specifically designated for geological sequestration of CO₂ under the Safe Drinking Water Act. The EPA's GHGRP Subpart RR was written to reference both, but the permitting requirements and the long-term stewardship obligations differ substantially. Class VI permitting requires a full site characterization, an area of review (AoR) analysis, and an approved post-injection monitoring plan. Most existing AGI wells were not designed or permitted to Class VI standards.

The "secure geological storage" standard. For §45Q purposes, the CO₂ must be disposed of in "secure geological storage" as defined under EPA rules implementing the credit. EPA Subpart RR (40 CFR § 98.1200 et seq.) defines the technical requirements for geological sequestration reporting—it is the reporting rule, not the injection well permitting rule, but satisfying Subpart RR is a prerequisite for §45Q. An AGI operator with a Class II injection well can potentially satisfy Subpart RR if they can demonstrate that CO₂ remains trapped in the formation and implement the required monitoring program.

In practice, some AGI wells in deep saline aquifer or depleted reservoir settings are being repermitted or supplementally characterized to support a Subpart RR compliance program. Whether this is cost-effective depends on the CO₂ volume, the credit value, and the cost of the monitoring program.

Measurement, Reporting, and Verification requirements

MRV is where most AGI operators encounter their first hard constraint. Subpart RR of 40 CFR Part 98 requires:

Flow measurement of the injection stream with a calibrated meter (Coriolis, turbine, or ultrasonic at required accuracy, typically ±1% of reading).
Compositional sampling to determine the CO₂ fraction of the acid gas—because you can only claim credits for CO₂, not for H₂S or water vapor in the stream.
Annual reporting to EPA via the GHGRP electronic reporting platform, including the calculated tonnes of CO₂ injected.
Third-party verification of the reported data by an accredited GHG verification body.

The compositional measurement requirement is significant for AGI operators: acid gas streams are typically 40–80% CO₂ by mole, with the balance being H₂S, water, and trace hydrocarbons. You must separate the CO₂ credit-eligible component from the total injection volume. A process simulator is directly useful here—building a model of the amine or acid gas removal unit, the compression train, and the injection wellhead gives you the mass balance to cross-check against metered data. The equation of state choice matters for the CO₂ density calculation at injection pressure; see GERG-2008 vs Peng-Robinson for when the difference is material for mass metering. Discrepancies between the simulation mass balance and the metered MRV data are an audit risk.

Economic thresholds and credit mechanics

At $85/tonne (PWA-compliant rate), the economic case for AGI §45Q compliance improvements depends heavily on CO₂ injection volume:

| CO₂ injected (tonnes/year) | Annual credit potential | |---|---| | 1,000 (minimum threshold) | $85,000/year | | 10,000 | $850,000/year | | 50,000 | $4,250,000/year | | 100,000 | $8,500,000/year |

A 50 MMscfd sour gas plant removing 10% CO₂ from the inlet gas injects roughly 30,000–50,000 tonnes/year of CO₂ (order of magnitude—actual depends on inlet composition and gas density). At that scale, the annual credit potential of $2.5–4.2M may justify the cost of Subpart RR compliance, which in our experience runs $200,000–$800,000 in capital for metering upgrades and $50,000–$200,000/year in ongoing monitoring and reporting costs. The economics are sensitive to credit transferability—the IRA allows credit transfers under §45Q(f), enabling operators to monetize the credit even without a tax liability, which changes the calculus for smaller operators.

The 12-year credit period means the total potential credit stream is 12× the annual figure above. Discounted at a reasonable rate, the NPV of a qualifying AGI project can easily justify the compliance investment at even modest CO₂ volumes.

Prevailing wage and apprenticeship requirements

The IRA made the full $85/tonne credit (for geological storage) conditional on prevailing wage and apprenticeship (PWA) compliance for all construction, alteration, and repair work on the facility during the credit period. For a new AGI compression and injection facility, this means:

All laborers and mechanics employed on construction must be paid at least the applicable Davis-Bacon Act prevailing wage for the type of work in the project county.
At least 15% of labor hours for construction must be performed by registered apprentices (phased in from 10% for projects beginning before January 1, 2024).
Maintenance work performed during the 12-year credit period that qualifies as "alteration or repair" under IRS guidance is also subject to PWA requirements.

Non-compliance with PWA does not eliminate the credit—it reduces the credit to the $17/tonne base rate. The decision to pursue PWA compliance is a project-level business decision that requires coordination with the EPC contractor and HR function.

When this gets harder

Mixed H₂S/CO₂ streams with variable composition. When the inlet sour gas composition varies seasonally or with reservoir depletion, the CO₂ fraction of the acid gas stream fluctuates. Subpart RR requires you to track these changes in your MRV calculation. A static assumption of, say, 65% CO₂ in the acid gas will under- or over-report the injected CO₂ mass and create audit exposure. A real-time or daily compositional measurement program—or a validated process simulation that produces composition versus time—is the solution.

Interaction with state environmental permits. State UIC programs often have requirements that can conflict with the Subpart RR monitoring program design. In some states, Class II AGI injection wells are not permitted to add CO₂ monitoring infrastructure without triggering a permit modification, which can take 6–24 months. Timeline risk is a real project consideration.

Transfer and monetization mechanics. IRC § 45Q(f) allows credit transfers, but the mechanics—eligible transferee identification, election filing, IRS Form 8933 completion—require tax counsel with specific §45Q experience. Valuation of transferred credits involves counterparty negotiation and depends on the buyer's tax appetite. This is not a DIY exercise.

Post-Inflation Reduction Act legislative uncertainty. Tax legislation in 2025–2026 has introduced modifications to the IRA framework. As of the publication of this article, operators should verify current credit rates, begin-construction deadlines, and PWA requirements against current IRS guidance and any enacted legislation since the IRA. The statutory text at 26 U.S.C. § 45Q is always the primary reference.

How Rankine handles this

Rankine's compliance certification engine is designed to support §45Q documentation for gas processing operations. For an AGI plant flowsheet, Rankine computes the mass balance across the gas treating and acid gas compression sections, producing a timestamped CO₂ injection rate that can be cross-referenced against metered MRV data. The audit log captures every simulation input and output with provenance—so when an MRV verifier asks how the CO₂ tonnage was calculated, you have a complete computational trail.

The compliance cert engine produces a structured output document that includes the facility description, the CO₂ mass balance methodology, the EOS used (PR with Peneloux correction for the high-H₂S acid gas stream), and references to the applicable regulatory sections. This is not a substitute for MRV metering or for tax counsel, but it provides the engineering basis that both require.

For operators evaluating simulation tools for §45Q compliance support, the HYSYS alternatives comparison covers how different simulators handle the kind of acid gas treating and injection modeling that §45Q compliance requires. Learn more about Rankine's compliance capabilities at the homepage.

FAQ

Does acid gas injection qualify for §45Q credits?

It can, but not automatically. The CO₂ component of the injected acid gas may qualify if the injection well meets the EPA UIC requirements for geological storage, the operator maintains a qualified facility under 26 U.S.C. § 45Q, and the CO₂ is measured, reported, and verified per EPA Subpart RR of 40 CFR Part 98. Facilities that inject acid gas solely for disposal—without meeting the monitoring and reporting requirements—do not qualify. The distinction between disposal and secure geological storage is a threshold question for tax counsel.

What is the §45Q credit rate for geological storage in 2026?

Under the Inflation Reduction Act of 2022, the base credit rate for CO₂ qualified for geological storage is $17/tonne, scaling to $85/tonne if the prevailing wage and apprenticeship (PWA) requirements are met for construction and operation. The $85/tonne rate is what makes most AGI projects economically significant. Credit rates are indexed to inflation starting in 2027. Projects that began construction before January 1, 2033 can claim the credit for 12 years.

What is the minimum capture threshold for §45Q eligibility?

Under 26 U.S.C. § 45Q, an industrial facility must capture and store at least 1,000 metric tonnes of CO₂ per year to qualify. Most AGI plants handling sour gas at any meaningful scale exceed this easily. However, the acid gas stream must be measured and the CO₂ component specifically quantified; total injection volume is not sufficient.

What does MRV mean in the context of §45Q?

MRV stands for Measurement, Reporting, and Verification. For §45Q, the IRS requires that CO₂ captured and stored be measured under EPA's GHGRP, specifically Subpart RR of 40 CFR Part 98. This means installing a metering system on the injection stream, submitting annual GHGRP reports to EPA, and having the reported data third-party verified. Without a Subpart RR-compliant MRV system, §45Q credits cannot be claimed.

Can an existing AGI plant claim §45Q credits retroactively?

No. §45Q credits are prospective—the credit accrues from the date the facility meets all qualification requirements. Injection that occurred before the facility achieved qualified status does not generate credits. The begin-construction date is relevant for PWA requirements; facilities that began construction after the IRA publication date must meet PWA requirements to access the full credit rate.