University of Kentucky researchers exploring potential uses for stillage, the sloshy, soup-like byproduct of Kentucky bourbon production, have converted the hard-to-treat material into an electrode for a ‘super’ supercapacitor.
The UK research team said that their stillage-derived ‘super’ supercapacitor stores more energy than similarly sized commercial devices, offering bourbon makers a potentially profitable outlet for the large amount of stillage they produce each year.
“This research presents an innovative, potentially scalable, and sustainable strategy for repurposing bourbon stillage into efficient, green, and high-performance materials for energy storage applications, with the potential to be adopted by the entire whiskey and ethanol production industry,” the researchers write.
The ‘Problem’ with the Raw Material that Makes up the Super Supercapacitor
Bourbon is a straight whiskey traditionally made from a mash containing at least 51% corn, along with malt and rye, and according to a recent statement, 95% of the world’s bourbon today is produced in the state of Kentucky.
All of that bourbon leaves behind an enormous amount of waste grain, which distillers call stillage. Josiel Barrios Cossio, a graduate student who recently presented the study at the American Chemical Society (ACS) 2026 annual spring meeting, explained that this process produces a disproportionate amount of stillage that is difficult to manage.
“From the final volume of bourbon produced, you get 6 to 10 times that amount of stillage as waste,” the researcher explained.
Although some of the stillage is sold to farmers as livestock feed or a soil additive, it is notoriously difficult to transport when wet. The material is also expensive and time-consuming to dry, a problem the UK grad student witnessed firsthand while working in Kentucky.
“So, it’s a big deal,” Barrios Cossio said.
Turning the Disadvantage of Wet Stillage into a Manufacturing Advantage
After exploring potential uses for the large volume of bourbon stillage produced each year, Barrios Cossio and colleagues decided to exploit its energy storage potential. The first step involved converting the soupy material into more valuable materials.
Called hydrothermal carbonization, the process is the equivalent of high-intensity pressure cooking. Critically, this process benefits from the typically challenging, watery condition of bourbon stillage, rather than requiring the material to be dried first.
Josiel Barrios Cossio.
“We could take the stillage as it is, in a dispersion with a lot of water, and use that disadvantage as an advantage,” Barrios Cossio explained.
The process also offers potential environmental benefits, since any electrodes made from the converted stillage would constitute a plant-based, sustainable electronic device. Still, the research team notes, although previous research has shown the potential of hydrothermal carbonization for converting corn fibers into usable carbon materials, the approach has never been tested with bourbon stillage, “which is made of a blend of grains that must include corn.”
Turning ZDistillery Waste Into Hard Carbon and Activated Carbon to Store Energy
After convincing distillery owners from Kentucky, Canada, and Illinois of their intentions, Barrios Cossio and the project’s principal investigator, UK chemist Marcelo Guzman, the team was allowed to collect stillage samples. Next, they converted the stillage into a fine black powder via hydrothermal carbonization. This included subjecting it to pressure and heat in a 10-liter ‘reactor.’
This base material allowed the team to create two different forms of energy-storing carbon. To form hard carbon, which is like graphite but with carbon sheets less neatly stacked, the UK team heated it to 392 degrees Fahrenheit (200 degrees Celsius) in a furnace. The resulting material’s composition makes it ideal for storing more lithium ions, thereby increasing its energy storage capability.
To turn their converted stillage into activated carbon, the team mixed it with potassium hydroxide and heated it to 1,472 F (800 C). The resulting, extremely porous form of carbon can use its large internal surface area to store large amounts of charge.
Super Supercapacitors Store Up to 25 Times More Energy Than Commercial Devices
To create their first prototype supercapacitor from stillage-derived activated carbon, the team constructed standard double-layer capacitors with a liquid electrolyte in between the two activated carbon electrodes. When the new capacitors were charged, tests revealed they could store up to 48 watt-hours per kilogram. The team noted that this performance was “on par” with commercially available devices.
Next, Barrios Cossio and Guzman used their stillage-derived carbon to make a supercapacitor. According to the team’s statement, this category of devices offers engineers a ‘compromise’ between the fast discharge speeds of ordinary capacitors and the higher energy storage capacity of batteries.
Because they were evaluating both the hard and activated carbon samples, the team built one capacitor-type activated carbon electrode and one battery-type hard carbon electrode. Next, both prototype devices were infused with lithium ions. When Barrios and Guzman tested their hybrid devices, the stillage-derived supercapacitors stored “up to 25 times the energy per kilogram” compared to conventional versions.
When highlighting the increased storage capacity of their suer supercapacitor compared to commercially available devices, the team also noted that they are a “new example of using one agricultural source for two different electrodes in a single device.”
“It was a huge discovery for me that you can make hybrid devices from this waste,” Barrios Cossio explained. “Hybrid devices are not common. Not common and not easy to make.”
Scientists Find Tackling a Real-World Problem ‘Super Cool’
Moving forward, the UK researchers plan to study the mechanisms underlying the superior energy storage capabilities of their supercapacitors, with an eye on optimizing the process for commercial applications. They are also working on larger versions of their prototype devices to offer the industry a sustainable alternative.
“One day, this technology could help stabilize the electrical grid as more renewable energy sources are incorporated,” they explained.
Outside the laboratory, Barrios Cossio and Guzman hope to perform a detailed life-cycle analysis, a technological feasibility assessment, and an overall economic evaluation of their device. Ideally, they will add up to a new, sustainable process for converting bourbon distillery stillage into useful, versatile, potentially valuable commercial products.
When discussing the personal benefits of the research, both scientists said they were “excited” to have discovered a possible solution for a local issue that has plagued the Kentucky bourbon industry.
“This project allowed us to link with a real-world problem with industries at our state level,” said Guzman, while also noting the team’s collaboration with Andrea Balducci’s group at the Friedrich Schiller University Jena, Germany. “And that was super cool.”
The study “Bourbon whiskey waste-derived carbons for electric double layer and Lithium-Ion supercapacitors” was presented at the spring meeting of the American Chemical Society (ACS), ACS Spring 2026.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.