NREL Biomass Technology a Cornerstone of SAFFiRE Renewables Biofuel Pilot Plant Going Up in Kansas

May 10, 2024

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by Erik F. Ringle (National Renewable Energy Laboratory) On its path to opening a facility designed to turn agriculture residue into a scalable biofuel business, SAFFiRE Renewables, LLC plans to break ground on its pilot plant near Liberal, Kansas, in late 2024.

In 2023, the company negotiated a license agreement for the National Renewable Energy Laboratory’s (NREL’s) deacetylation and mechanical refining (DMR) process, a technology seen as important for sidestepping challenges with cellulosic biofuel facilities in the past. DMR uses a “gentle” alkaline bath and a mechanical shredder to prepare corn stover for ethanol fermentation—essential steps for accessing the energy-dense sugars locked inside.

Ultimately, ethanol made at the plant, which will be operated by Conestoga Energy, can be upgraded into sustainable aviation fuel (SAF) using LanzaJet’s alcohol-to-jet technology. Estimates suggest the resulting SAF will have a carbon footprint at least 83% lower than conventional jet fuel.

According to Anthony Gregory, SAFFiRE’s chief operating officer, the planned construction of the pilot plant reflects the advantage of national laboratory–industry partnerships for enabling cornerstone technologies like DMR to make an impact in the real world.

“NREL has put in a decade of research on DMR that has been shown to not only solve many of the preexisting problems with cellulosic ethanol but also to have new advantages for processing biomass,” he explained. “Now, the lab’s research is being taken up by a commercial entity that plans to scale it and put it into production as a continuous, integrated process. It’s a great example of the different skills that the public and the private sectors can bring to the table.”

Initial funding for the plant was provided by the U.S. Department of Energy (DOE) Bioenergy Technologies Office (BETO), with a 50% match from Southwest Airlines. Southwest has the option of purchasing SAFFiRE’s cellulosic ethanol—and the subsequent SAF—to fuel its aircraft.

“The funding award from BETO was key for launching our new technology,” said Michael Himmel, the co-principal investigator of the project. “This permitted NREL scientists and engineers to collaborate closely with industry to scale our patent-pending DMR pretreatment process.”

With a potential buyer in place, fuel credits available, and NREL’s DMR technology, SAFFiRE aims to take cellulosic ethanol to where it struggled to go in the past.

“The announcement of this pilot facility in Liberal, Kansas, is huge,” said Eric Payne, the NREL senior licensing executive who manages NREL’s DMR intellectual property. “It's the phoenix that is rising from the ashes of the now defunct second-generation ethanol industry, and that's a big deal for federal SAF goals.”

Gentle Pretreatment: How NREL DMR Sidesteps Roadblocks to Cellulosic Biofuels

A chart comparing DMR and dilute acid pretreatment.

NREL’s deacetylation and mechanical refining (DMR) process combines low-severity chemical pretreatment and mechanical refining to sidestep the expenses and challenges of traditional pretreatments.

Depending on the process used to make it, biofuel made from lignocellulose—the fibrous, often cast-off parts of plants—can net deep reductions in greenhouse gas emissions compared to fossil fuels and even first-generation biofuels. According to DOE’s Alternative Fuels Data Center, for example, ethanol made from lignocellulosic corn leaves, stalks, and cobs can reduce emissions by 88% to 108% on a life-cycle basis compared to conventional jet fuel.

According to NREL scientist Nancy Dowe, however, past efforts to commercialize these “cellulosic biofuel” technologies uncovered real challenges.

“A lot of the failures of old cellulosic ethanol plants were not so much on the conversion side of things,” she explained. “It really was around material handling and pretreatment—basically opening up that plant structure for enzymes to come in and break it down into sugars.”

Old cellulosic biofuel technologies used highly specialized equipment that relied on acids, heat, and high pressures to remove impurities from the corn stover—such as acetate, lignin, and ash. While those processes were highly effective at breaking down the plant material, their extreme operating conditions created persistent headaches at industrial facilities. The acids corroded expensive equipment over time. Clogs formed as the shredded stover was fed into high-pressure reactors.

According to Gregory, those issues made it difficult to scale facilities to process thousands of tons of biomass a day.

“A commercially viable process needs to operate with very high reliability, generally running continuously at least 90%–95% of the time,” Gregory said. “When you’re pumping solids around, you want to minimize plugs and holdups.”

NREL’s DMR technology emerged to address these recognized challenges with cellulosic biofuel production. A research team—including NREL’s Dowe, Michael Himmel, Xiaowen Chen, and many others—responded by systematically reinventing biomass pretreatment with attention to past challenges.

“NREL took a step back to look at the big picture and began asking: ‘What are some of the major issues we are seeing?’” Dowe explained.

The result is a technology that uses mechanical refiners already common in the paper industry—cutting capital costs. DMR relies on noncorrosive chemicals to lower toxicity. Perhaps most importantly, it uses nonpressurized tanks that work at low temperature and pressure, rather than high-pressure reactors, making it easy to rapidly feed large volumes of biomass. Small-scale studies suggest these advances can lower capital and operating expenses and increase the efficiency and ease of making sugars fermentable to ethanol.

From Liberal, Kansas, to Soperton, Georgia: Turning Ethanol Into Sustainable Aviation Fuel

SAFFiRE expects the pilot plant to handle 10 tons of corn stover every day, which could translate to an output of roughly 0.3 million gallons of cellulosic ethanol every year. Although that is a fraction of the nearly 100 million gallons produced annually from the much larger corn ethanol facility on site, SAFFiRE plans to use the pilot plant as the first in a series of progressively larger facilities.

“Part of our strategy has been to be systematic because when it comes to new technology, you should not skip steps in scaling,” Gregory explained. “We are working to take a methodical approach to developing the technology.”

The idea, Gregory said, is to resolve technical issues and develop robust business plans, local supply chains, and relationships with suppliers and vendors. For example, SAFFiRE and Southwest are conducting in-depth analyses on the ethanol market, the SAF market, and available tax credits—aiming to smooth the pathway to build more, larger plants elsewhere across the United States in the coming decade.

For now, the plan for the pilot plant is to ship ethanol made in Liberal, Kansas, to a Georgia facility owned by LanzaJet, which uses a proprietary process to turn ethanol into SAF. In the future, that model might be replicated and scaled to respond to rapidly increasing demand for the renewable jet fuel—demand driven by state and federal biofuel incentives as well as SAF purchase agreements from large U.S. airlines, including Southwest.

According to Gregory, a successful SAFFiRE pilot plant would have resounding impacts across industries.

“I think this is good for so many different industries in the United States,” he said. “This is good for the agriculture industry. This is good for the corn ethanol industry. This is good for the airline industry, and it can create jobs that are going to be here in the U.S.”

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