Stillage is being turned into electrodes in Kentucky, US. Kentucky’s bourbon whiskey boom leaves behind a huge amount of waste grain called stillage. Now, that waste is being recycled into an energy-storage material that could be part of future commercial electronics.

Researchers at the University of Kentucky will present the sustainable solution at the ACS Spring 2026 meeting. 

This project offers an alternative to a byproduct that distilleries currently find difficult and expensive to manage.

It shows that bourbon byproducts can produce supercapacitors with superior storage capacity compared to existing commercial models.

“From the final volume of bourbon produced, you get 6 to 10 times that amount of stillage as waste. So it’s a big deal,” said Barrios Cossio, a graduate student associated with the project. 

Conversion process

To develop high-performance supercapacitors, bourbon stillage was targeted as a sustainable, plant-based carbon source for electrode materials. 

While other plant fibers have been explored, this team was the first to harness the unique grain profiles of bourbon stillage.

Stillage is a heavy, moisture-rich byproduct that is typically difficult to transport or costly to dry for use as animal feed. 

Rather than fighting the moisture, the new study leveraged the mash’s soupy consistency to streamline the production of high-value carbon materials.

The drying stage was entirely eliminated by using hydrothermal carbonization — a process similar to high-pressure cooking. 

Success required more than just chemistry. 

The researchers spent months building partnerships with distilleries across Kentucky, Illinois, and Canada to gain access to the samples needed for their fun energy-storage experiments.

Using a 10-liter reactor, heat and pressure were applied to turn soggy stillage into a fine black powder, which was then refined in a furnace into two distinct materials.

The powder was then heated to 200°C (392°F) to form hard carbon, whose disordered structure is perfect for trapping lithium ions to boost energy storage.

Alternatively, by adding potassium hydroxide and heating it to 800°C (1472°F), they produced activated carbon, a highly porous material with a massive internal surface area for holding electrical charge.

25 times more energy

The experiments were validated by building two types of coin-sized storage devices using stillage-derived carbon.

First, the double-layer capacitors with activated carbon electrodes met current commercial standards, achieving an energy density of 48 Wh/kg. 

However, the real breakthrough came with their hybrid lithium-ion supercapacitors. It consisted of a battery-like hard-carbon electrode and a capacitor-style activated-carbon electrode. 

The resultant device blends fast discharge speeds with massive storage capacity, holding up to 25 times more energy per kilogram than conventional versions.

This project marks a rare milestone in materials science by using a single agricultural waste source to produce both types of electrodes required for a high-performance hybrid device. 

Having proved the concept at a small scale, the researchers are now shifting toward commercialization, focusing on scaling up the technology to support large-scale electrical grid stabilization. 

The immediate roadmap includes conducting rigorous life cycle and economic feasibility analyses to ensure that transforming distillery waste into energy storage is as sustainable and cost-effective as it is innovative.