NREL Analysis Shows Midwestern Electrofuels Could Become Energy Superheroes

by Zia Abdullah (National Renewable Energy Laboratory) More ethanol, fewer emissions, land with multiple purposes—there are several advantages of using renewable electricity to increase the carbon efficiency of biorefineries. -- ... Made from carbon dioxide (CO₂) from industrial waste gases or directly from the air, e-fuels defy conventional wisdom on how liquid fuels are made. Although e-fuels may be technological marvels, they don’t come from another planet. They come from America’s corn belt, or at least they soon could according to new analysis from the National Renewable Energy Laboratory (NREL).

Every hour, a typical 90-million-gallon ethanol plant produces around 27 tonnes of CO₂, a natural byproduct of fermentation. These waste streams of CO₂ are highly concentrated—almost pure CO₂—which makes them a choice ingredient—or feedstock—for making e-fuels by outfitting refineries with electrolyzers. When given an electrical charge, electrolyzers catalyze chemical reactions that split and reconfigure CO₂—a stable molecule—into compounds easier to upgrade into energy-dense fuels and chemicals. In this way, electrolyzers can turn CO₂ that would have been released into the atmosphere into valuable chemicals instead. Doing so could not only greatly lower the carbon intensity of ethanol— already with 44%–52% lower greenhouse gas (GHG) emissions than gasoline—but also boost the fuel output of existing facilities.

By how much? Ongoing research from the CO₂ Reduction and Upgrading for e-Fuels Consortium (CO₂RUe), funded by the U.S. Department of Energy’s Bioenergy Technologies Office (BETO), is demonstrating how specialized microbes can metabolize the products made from CO₂ electrolysis into ethanol. That research shows an average biorefinery outfitted with electrolyzers and bioreactors could produce as much as 41 million more gallons of ethanol every year.

Think about the potential at a given facility: CO₂ could go from a waste product to the basic ingredient for making up to 50% more ethanol —with a carbon footprint even smaller than today’s corn ethanol. All that’s left is finding an abundant new source of renewable electricity to power the electrolyzers.

When Making Ethanol is a Breeze

Where Wind and Corn Are King—The states that grow the most corn are among the windiest in the country, providing amply opportunity to co-locate turbines in corn fields to supply power to electrolyzers.

Among the windiest parts of the country, corn belt states have long been leaders in wind energy capacity, and are positioned to wield that affordable and abundant resource to make e-fuels. According to NREL analysis, there is ample space for wind turbines in existing corn fields to convert all CO₂ from fermentation back into ethanol.

Here’s how the math works for a single, first-generation ethanol plant. It would require 40 megawatts of renewable electricity to power enough electrolyzers to convert approximately half of the hourly output of CO₂ into carbon monoxide (CO). Another 165 megawatts is needed to produce clean hydrogen for biologically transforming that CO into more ethanol.

Running at 35% capacity, approximately 200 wind turbines could cover this new demand, and there is ample land to install those turbines in existing corn fields without impacting normal farm operations. In fact, those turbines could be co-located on the approximately 160,000 acres already used to supply a typical ethanol plant.

Reviewing the larger corn ethanol landscape puts these numbers into context. With nearly 200 ethanol plants across the country, countless acres of corn fields, and rapidly falling wind energy costs, midwestern e-fuels could be set to revolutionize the ethanol industry.

E-fuels are exactly the kind of innovation—call it superpower—we need to meet robust goals to decarbonize transportation, the single largest source of carbon emissions in the United States. Through the Sustainable Aviation Fuel (SAF) Grand Challenge, the federal government aims to boost the production of low-carbon SAF to 35 billion every year by 2050. That’s enough sustainable fuel to cover all anticipated future demand.

Harnessing feedstocks like CO₂ alongside the nation’s abundant renewable carbon resources is critical for meeting these bold fuel targets. As BETO-funded researchers have demonstrated, emerging alcohol-to-jet technologies are capable of converting ethanol (whether made from corn starch, corn stover, or waste CO₂ from fermentation) into high-performance SAF to meet this demand.

Of course, more targeted research and analysis is essential to improve the readiness of these and other e-fuel processes. Along with technology development, we need innovative business models to seamlessly coordinate transactions between ethanol refineries and wind energy providers. That way, ethanol refineries can focus on what they do best: produce ethanol. Through CO₂RUe and other BETO-funded research, NREL and partner institutions are working tirelessly to identify and overcome key barriers to these promising new technologies.

As technologies mature and demand grows for low-carbon SAF from all corners of the country, this NREL analysis raises an exciting and provocative question. 44 million metric tons of pure CO₂ from ethanol plants every year; ample wind resources; robust ethanol supply chains; a network of existing biorefinery infrastructure—could these be the underpinnings of a heroic SAF revolution? READ MORE