A byproduct of Kentucky bourbon need not be a hangover. The enormous volumes of waste grain, or stillage, generated by bourbon distilleries can be harnessed to design supercapacitors with superior storage capacity compared to existing commercial models.

University of Kentucky researchers sought to leverage the soupy consistency of stillage to streamline the production of high-value carbon materials in a hydrothermal carbonization process for use as electrodes. 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 to form hard carbon, which is ideal for trapping lithium ions and boosting energy storage. The addition of potassium hydroxide formed activated carbon, a highly porous material with a large internal surface area for holding electrical charge, when the powder was heated to 800° C.

Two types of coin-sized storage devices were then constructed with the stillage-derived carbon. First, a liquid electrolyte was placed between activated carbon electrodes to form double-layer capacitors. Testing confirmed the capacity to store up to 48 Wh/kg, on par with commercially available devices. Hybrid lithium-ion supercapacitors, consisting of a battery-like hard-carbon electrode and a capacitor-style activated-carbon electrode, were also engineered. The resultant device blends fast discharge speeds with enlarged storage capacity, holding up to 25 times more energy per kilogram than conventional versions.

The research presented at the recently held American Chemical Society Spring 2026 program proves that supercapacitor components can be sauced – er, sourced – from the bourbon distillation process.