Calumet Inc. subsidiary Montana Renewables LLC has revised its previously announced sustainable aviation fuel (SAF) expansion, or MaxSAF project, at the operator’s renewable fuels manufacturing plant in Great Falls, Mont.

Montana Renewables now estimates remaining expansion capital at $137 million, compared with about $1.2 billion contemplated under the original Phase 2 project, Calumet said in a release Sept. 1.

The revised plan proposes repurposing and redeployment of existing equipment from the adjacent Calumet Montana Refining (CMR) asphalt plant that will be transferred to Montana Renewables under a long-term lease.

Specific assets planned for repurposing and transfer from CMR include a hydrotreater, hydrogen plant, and naphtha splitter. The tied-in hydrotreater ultimately will create a proprietary dual-reactor configuration at the renewable fuels plant, according to Calumet.

The second reactor will operate in a “polishing” service rather than the conventional “cracking” service to achieve a configuration aimed at improving SAF yields, reducing by-product formation, and limiting yield loss.

Additional modular equipment, including a third renewable fuels reactor currently located offsite, could support capacity increases beyond 200 million gal/year, Calumet said.

The revised program consists of six discrete projects rather than one large construction effort, with each project designed to remove specific operating constraints and enable a shorter payback period.

Montana Renewables currently produces SAF at an estimated rate of 60 million gal/year rfollowing constraint-removal work completed during a spring 2026 turnaround, according to Calumet.

In the near-term and following the proposed expansion, the parent company said it expects SAF production at Montana Renewables’ plant to:

• Exceed an 80-million gal/year rate by yearend 2026.
• Surpass 120 million gal/year by spring 2027.
• Reach about 200 million gal/year by yearend 2028.

The expansion also will result in recovery of about 20 million gal/year of renewable propane and butane previously used as fuel gas. The plan includes improved renewable naphtha yields and lower unit operating costs via higher throughput and reduced water consumption, Calumet said.

Feedstock consumption at the renewable fuels plant will reach about 2 billion lb/year of ranch- and farm-originated materials used to produce renewable jet fuel, diesel, and gasoline.

While equipment tie-ins as part of the expansion are scheduled to be completed during a fourth-quarter 2026 turnaround, Calumet said CMR will continue producing retail asphalt and retain its employees. Post-expansion, CMR and Montana Renewables also will share unidentified site infrastructure and other costs.

Announced in 2023, the original MaxSAF plan called for increasing Great Falls SAF production by more than 700% to about 300 million gal/year. Combined SAF and renewable diesel capacity at the time was anticipated to reach about 330 million gal/year.

The original project also included a second renewable fuels reactor, debottlenecking of renewable fuels and feedstock pretreatment units, SAF blending and logistics equipment, expanded renewable hydrogen production, cogeneration, and water treatment and recycling systems.

Financing and loan revision

The revised MaxSAF project follows an amendment to the loan guarantee agreement between Montana Renewables and the US Department of Energy (DOE) originally executed in January 2025.

The DOE’s Phase 2 funding commitment has been reduced to a single final draw of $34 million from up to $658 million in the original agreement. Calumet said Montana Renewables expects to fund the balance of the revised expansion through retained earnings.

The amended structure does not require third-party equity, which Calumet said eliminates additional dilution while maintaining a simpler capital structure.

Funded in February 2025, the first DOE tranche totaling $782 million recapitalized Montana Renewables and supported eligible previously incurred expenses. Calumet also made a $150 million equity investment using cash on hand.

Under the now-amended agreement, the final $34 million draw remains subject to commercial, technical, and legal conditions. During construction, Calumet said it expected retained earnings to supplement DOE funds and keep debt below 55% of eligible project spending.

The loan retains its 15-year tenor and annual interest rate of the US Treasury rate plus 3/8%. Principal and interest payments remain deferred until MaxSAF is commissioned.

The first debt-service date remains March 2029, with maturity in December 2039.