Kentucky produces an astounding 95% of the world’s bourbon whiskey, a process that generates substantial amounts of stillage—spent grains left after distillation. The volume of this byproduct is staggering; for every barrel of bourbon made, six to ten barrels of stillage remain. Traditionally, this sticky, water-rich waste has been sold as livestock feed or soil fertilizer. However, the challenges of transportation and drying costs have long posed logistical and economic hurdles for distilleries aiming to manage this biomass.

Enter hydrothermal carbonization (HTC), a technique analogous to pressure cooking that converts wet biomass directly into carbon-rich materials. By applying this high-pressure, high-temperature process to stillage, the research team transformed this unwieldy waste into a dry, fine, black carbon powder. This is a critical step, as carbon-based materials are fundamental components in fabricating electrodes for supercapacitors—a class of devices known for rapid energy storage and release.

The conversion process involved subjecting the stillage to HTC in a reactor capable of handling large volumes, ensuring scalability beyond laboratory trials. Following this, the carbon powder was further processed through pyrolysis, heating it to temperatures around 200 degrees Celsius to produce hard carbon. Alternatively, a higher temperature treatment at 800 degrees Celsius with potassium hydroxide (KOH) activation produced activated carbon known for its highly porous structure. These two distinct carbon forms offer complementary electrochemical properties suitable for different supercapacitor designs.

Hard carbon exhibits a disordered layered structure that facilitates lithium-ion intercalation, essential for lithium-ion hybrid supercapacitors. Activated carbon, with its extensive internal surface area due to its porous nature, excels in electric double-layer capacitors (EDLCs). These characteristics make the stillage-derived carbons uniquely suited for developing next-generation energy storage devices that combine high energy density with rapid charge-discharge cycles.

For proof-of-concept, the team constructed coin-sized supercapacitor cells by sandwiching liquid electrolytes between pairs of activated carbon electrodes. Remarkably, these devices demonstrated energy storage capabilities on par with commercial supercapacitors, reaching up to 48 watt-hours per kilogram. This performance metric places the stillage-derived materials as competitive alternatives in the energy storage market, with the added benefit of valorizing industrial waste.

Taking innovation further, the researchers engineered hybrid lithium-ion supercapacitors by pairing a lithium-ion infused hard carbon electrode with an activated carbon electrode. These hybrid devices marry the high power density and durability of capacitors with the superior energy storage of lithium-ion batteries. The stillage-derived hybrid supercapacitors exhibited energy densities up to 25 times greater than conventional counterparts, marking a substantial leap in sustainable energy technology.

Beyond just material development, this research underscores a novel circular economy model where an agricultural byproduct is repurposed for advanced technological applications. The interdisciplinary team collaborated extensively with distillery owners across Kentucky, Illinois, and Canada, ensuring a steady supply of raw material while fostering industry-academic synergies that could facilitate real-world implementation.

Comprehensive physicochemical characterization confirmed the suitability of these carbons for energy storage applications. Techniques such as Raman and Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), and nitrogen physisorption elucidated the structural and chemical properties critical for electrochemical performance.

Electrochemical testing involved cyclic voltammetry, galvanostatic charge-discharge profiling, and electrochemical impedance spectroscopy, providing in-depth insights into charge storage mechanisms and device efficiency. The activated carbon electrodes exhibited excellent stability, retaining 96% of their capacitance over 15,000 charge-discharge cycles, a testament to their durability and potential longevity in practical applications.

Looking ahead, the research team plans to delve deeper into optimizing the energy storage mechanisms, scaling up device dimensions, and refining electrode fabrication techniques. Such advancements could pave the way for integrating these supercapacitors into electrical grids, particularly to stabilize fluctuating inputs as renewable energy sources become increasingly prevalent.

Economic and life cycle assessments are underway to evaluate the commercial viability and environmental impact of deploying this technology at industrial scales. Early findings suggest that transforming bourbon stillage into high-performance energy storage materials could reduce waste management costs for distilleries while contributing to greener, more sustainable battery and capacitor production.

This innovative project not only addresses a pressing problem at the state level but also signals a wider paradigm shift in how agricultural waste streams are valorized. Collaborations with international partners, including the Friedrich Schiller University Jena in Germany, highlight the global relevance of such sustainable technological solutions.

Funded by the U.S. National Science Foundation and the University of Kentucky, this work was presented at the spring 2026 meeting of the American Chemical Society (ACS), drawing attention from a broad audience of chemists, materials scientists, and energy engineers. The compelling fusion of waste valorization and cutting-edge energy storage underscores the transformative potential of chemistry to enable sustainable advances.

As society increasingly prioritizes circular economy principles and renewable energy integration, the ability to convert industrial residues like bourbon stillage into value-added carbon materials could become a cornerstone of sustainable technology development. The University of Kentucky’s breakthrough exemplifies how regional resources can be leveraged for global impact, turning what was once waste into a powerhouse of energy innovation.

Subject of Research: Bourbon whiskey waste-derived carbons for supercapacitors

Article Title: Bourbon whiskey waste-derived carbons for electric double layer and Lithium-Ion supercapacitors

News Publication Date: March 25, 2026

Web References:
https://acs.digitellinc.com/live/36/page/1271

Image Credits: Josiel Barrios Cossio

Keywords

Bourbon stillage, hydrothermal carbonization, supercapacitors, activated carbon, hard carbon, lithium-ion supercapacitors, energy storage, waste valorization, sustainable materials, electrochemical performance, circular economy, Kentucky bourbon industry

Supercapacitors are rapidly becoming a focal point for energy storage solutions, offering the ability to deliver rapid bursts of energy and significantly extend the lifecycle of electronic devices. Their efficiency and performance can be substantially improved through proper electrode engineering. In this groundbreaking study, researchers, led by R. Farma, employed activated carbon derived from mahogany seed shells, enhanced further by the incorporation of carbon nanotubes. This dual-material approach opens new avenues in supercapacitor technology.

Mahogany seed shells represent a ubiquitous agricultural waste product that has generally been overlooked. Traditionally discarded or underutilized, these shells provide an excellent resource for creating activated carbon, a key component in various energy storage applications. The researchers’ meticulous method involved the thermal activation of these shells, resulting in a porous carbon structure ideal for electrochemical applications. This not only mitigates waste but also capitalizes on sustainability principles, merging waste management with innovative energy solutions.

In the activation process, the cellulose-rich mahogany seed shells undergo thermal decomposition, leading to a carbonized material that exhibits high surface area and porosity. These characteristics are critical for supercapacitors, where increased surface area correlates strongly with energy storage capacity. The present research provides evidence that mahogany seed shells can yield activated carbon with outstanding performances comparable to commercially available materials. This discovery is a significant stride toward greener materials in electrical engineering.

Moreover, the inclusion of carbon nanotubes enhances the performance of the activated carbon electrodes dramatically. Carbon nanotubes, renowned for their exceptional conductivity and structural integrity, improve the overall conductivity of the electrode material. Their unique one-dimensional structure offers pathways for electron transport, thereby facilitating rapid charge and discharge rates. This synergy between activated carbon from mahogany seed shells and carbon nanotubes positions the electrodes for superior functionality in energy storage systems.

The environmental implications of such a study are profound. By converting waste agricultural materials to high-value products, we not only reduce landfill contributions but also minimize the need for synthesizing more carbon technologies that heavily rely on fossil fuels and environmentally detrimental practices. The researchers advocate that this approach can serve as a model for other waste materials, creating a ripple effect across various industries striving for sustainability.

Energy-related applications serve as a crucial context for this research. With the global demand for efficient energy storage rising due to the proliferation of renewable energy resources, the development of sustainable materials for supercapacitors is more critical than ever. This study sheds light on how agricultural waste can be transformed into functional materials that significantly contribute to energy transition efforts. There is an unrealized potential in tapping into natural resources that abound in many regions, which presents opportunities for greener technologies.

Furthermore, the optimization of the synthesis process involved fine-tuning parameters such as temperature and activation time. This meticulous research allowed for an understanding of how various conditions could affect the surface morphology and electrochemical properties of the activated carbon. By experimenting with these variables, the researchers successfully maximized the performance metrics of the derived supercapacitor electrodes, paving the way for industrial applications.

The practical implications of using mahogany seed shells extend beyond mere academic interest; they address real-world utility in businesses and industries focused on renewable energy solutions. In a world increasingly conscious of carbon footprints, the potential for utilizing agricultural waste offers a sustainable pathway for future innovations in energy technologies. As this research gains traction, it highlights an essential narrative: sustainability in energy solutions can emerge from the most unexpected places.

As the research community eagerly anticipates further developments, the groundwork laid by this study functions as a catalyst for ongoing innovation. The implications for further exploration of agricultural waste are substantial. Whether it’s exploring different types of seed shells or other organic waste products, this research underscores the importance of interdisciplinary approaches in addressing global challenges.

The future of energy storage technologies holds immense promise when empowered by sustainable materials engineering. Each advancement, such as the one stemming from the activation of mahogany seed shells and carbon nanotubes, reinforces a narrative of synergy between technology, sustainability, and innovation. With continued research and development, the prospect of cleaner technologies that benefit both consumers and the environment draws nearer.

This enthusiasm for sustainability is mirrored in the broader scientific community. With collective efforts in interdisciplinary research, the potential for breakthroughs in supercapacitors expands. Other materials may be identified that mirror or exceed the properties demonstrated in this study, creating a continuous cycle of innovation. The pathway forward is certainly illuminated, and it beckons an era where waste becomes a resource, and sustainability is woven into the very fabric of technological advancement.

In conclusion, the research led by R. Farma and colleagues offers exciting prospects for sustainable energy storage solutions through ingenious material innovation. The synthesis of supercapacitor electrodes from mahogany seed shells-derived activated carbon modified with carbon nanotubes brings a unique approach to overcoming energy storage challenges. As the study sheds light on the capabilities of agricultural waste, it serves as a reminder of the importance of rethinking our approach towards energy materials and the significance of sustainability in shaping our future.

Subject of Research: Sustainable supercapacitor electrodes from agricultural waste

Article Title: Sustainable supercapacitor electrodes from mahogany seed shells-derived activated carbon modified with carbon nanotubes.

Article References:

Farma, R., Sitinjak, P.E., Apriyani, I. et al. Sustainable supercapacitor electrodes from mahogany seed shells-derived activated carbon modified with carbon nanotubes.
Ionics (2025). https://doi.org/10.1007/s11581-025-06716-0

Image Credits: AI Generated

DOI: https://doi.org/10.1007/s11581-025-06716-0

Keywords: Supercapacitors, activated carbon, sustainability, mahogany seed shells, energy storage, carbon nanotubes.