Every barrel of bourbon leaves something behind. Not just future hangovers, but a thick, wet byproduct called stillage. For years, distilleries treated that material as a disposal problem. Now it looks more like an opportunity.
Chemists at the University of Kentucky found a way to turn that waste into something far more valuable. Their team developed a process that converts bourbon stillage into carbon materials used in advanced energy storage devices.
Behind every bottle of bourbon are vats of waste materials. Most of that unwanted trash is stillage—a goopy, mushy mixture of grains and corn. And in Kentucky—where 95 percent of the world’s bourbon is produced—there is a lot of stillage.
“From the final volume of bourbon produced, you get 6 to 10 times that amount of stillage as waste,” University of Kentucky chemist Josiel Barrios Cossio explained in a statement. “So it’s a big deal.”
Although stillage is often sold to farmers for livestock feed and soil enrichment, it’s a tricky material to handle. Transporting it is difficult given how watery it is, but it’s also exorbitantly expensive to dry. However, if there were uses that justified the costs of turning stillage into different materials, it could offer a convenient and comparatively eco-friendly solution to the ongoing predicament. And that’s exactly what Barrios Cossio and his colleagues set out to accomplish.
Kentucky produces about 95% of the world's bourbon, meaning the state also produces enormous amounts of stillage. For every gallon of bourbon, distilleries generate several gallons of leftover mash. That material holds mostly water, which makes it expensive to transport or dry, so much of it ends up as low-value livestock feed or waste that needs handling.
The research team decided to treat stillage as a raw material instead of a burden, placing the waste into a reactor, applying heat and pressure, and creating a fine black carbon powder. From there, they refined it into two useful forms: one version, called hard carbon, stores lithium ions efficiently. The other version, called activated carbon, contains a large internal surface area that stores electrical charge.
The process involves heating the powder in a furnace to create two distinct types of carbon electrodes:
- Hard carbon—produced at 1,832 ºF, this material is ideal for absorbing lithium ions to boost energy storage.
- Activated carbon—created at 1,472 ºF , this highly porous material can store massive amounts of charge.
“It was a huge discovery for me that you can make hybrid devices from this waste,” Barrios Cossio said. “Hybrid devices are not common. Not common and not easy to make.”
In performance tests, the team’s hybrid lithium-ion supercapacitors stored up to 25 times more energy per kilogram than conventional versions. Furthermore, their double-layer capacitors showed remarkable durability, retaining 96% of their capacity even after 15,000 cycles. The team collaborated with local distilleries across the region and partnered with researchers at Friedrich Schiller University Jena in Germany to develop the prototype.
“This project allowed us to link with a real-world problem with industries at our state level,” Guzman said. “And that was super cool.”
Those materials power devices known as supercapacitors. Unlike traditional batteries, supercapacitors quickly charge and last through hundreds of thousands of cycles. The activated carbon electrodes developed from stillage reached energy levels around 48 watt-hours per kilogram, which puts them in line with top commercial options.
The real step forward came from combining the two materials. The team built hybrid supercapacitors that pair hard carbon with activated carbon in a single device. That setup increased energy storage by about 25% compared to standard commercial designs, closing the gap between fast-charging devices and higher-capacity batteries.
For a proof-of-concept, the team made double-layer capacitors by sandwiching a liquid electrolyte between activated carbon electrodes. In tests, these coin-sized supercapacitors could store up to 48 watt hours per kilogram, which was on par with commercially available ones.
The researchers also experimented with hybrid lithium-ion supercapacitors, which are designed to compromise between the fast discharge speeds of capacitors and the higher energy storage of batteries. So, they built devices with one capacitor-type activated carbon electrode and one battery-type hard carbon electrode, which were both infused with lithium ions. These stillage-derived supercapacitors stored up to 25 times the energy per kilogram as conventional versions.
The lithium-ion supercapacitors are also 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,” says Barrios Cossio. “Hybrid devices are not common. Not common and not easy to make.”
Applications stretch across several industries. Electric vehicles use supercapacitors for regenerative braking systems. Power grids rely on them to handle quick energy swings from solar and wind. Consumer electronics benefit from fast bursts of power without long recharge times. Each of those uses value, durability, and speed, which is precisely where supercapacitors perform best.
The approach also solves a practical problem for distilleries. Stillage piles up fast, and disposal costs add up. Turning that material into high-value carbon reduces waste while creating a new revenue stream while also avoiding relying on mined or synthetic materials that carry higher costs and environmental concerns.
There's something fitting about the cycle: bourbon production creates the byproduct, and the byproduct becomes a building block for modern energy storage. The same industry that depends on tradition could now feed a technology tied to the future.
Barrios Cossio described the hybrid design as a major step because these systems remain difficult to build and refine. His team continues to test ways to improve performance and scale the process. Early results already show that carbon derived from stillage can compete with materials that cost far more to produce.
Energy demands continue to rise as more systems move toward electrification. Storage technology needs to keep pace. Finding abundant, low-cost materials makes that challenge easier to meet. Bourbon stillage checks both boxes.
So yes, every pour plays a small role in something bigger. Distilleries continue to produce, the waste continues to flow, and the research keeps advancing.
And if the future ends up powered in part by what gets left behind in a bourbon barrel, it's a trade worth making.
I promise that I will do whatever is demanded of me for such a worthwhile project. One pour into the breach, my friends.
