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

The researchers embarked on a novel “co-design” paradigm that integrates material structure and electrolyte chemistry to harness synergistic benefits. Rather than independently optimizing the solid electrode and the liquid electrolyte, this approach tailors both components to work harmoniously as a unified system. Central to this feat was the transformation of lignin, an abundant and renewable biopolymer derived from plant cell walls, into a hierarchical porous carbon electrode. This engineered carbon features meticulously controlled pore sizes on the sub-nanometer scale, optimizing ion accommodation and interaction dynamics to maximize energy storage potential.

Complementing this structural innovation, the electrolyte formulation was specifically engineered to match the unique porosity and chemistry of the electrode. By incorporating a weakly solvating lithium-based electrolyte interspersed with a specialized fluorinated diluent, the team effectively suppressed parasitic electrochemical reactions at elevated voltages. The fluorinated diluent acts as a molecular shield, preventing the degradation pathways that typically limit the voltage range and stability of conventional electrolytes, thus maintaining a consistent and durable interface under the rigorous conditions of high-voltage cycling.

This tailored electrode-electrolyte interplay enabled the device to operate stably at an unprecedented 4.0 volts—twice the typical voltage limit for most supercapacitors—without succumbing to rapid self-discharge or capacity fade. The advancement addresses a critical trade-off in energy storage technology: balancing power delivery speed with energy retention over extended periods, a feat previously deemed incompatible. The geometric confinement of solvated lithium ions within the lignin-derived carbon pores effectively concentrates charge carriers, thereby boosting the stored energy density immensely within a stable electrochemical environment.

One of the most striking achievements of this research is the device’s energy density, reaching an impressive 77.4 watt-hours per kilogram. This figure blurs the conventional boundary separating supercapacitors from batteries, indicating a paradigm where rapid charging capability no longer excludes substantial energy storage. The effective utilization of biomass-derived carbon material not only promotes sustainability but also leverages natural molecular architectures with inherent advantages for high-performance energy devices.

Stability and longevity often remain the Achilles’ heel for high-energy supercapacitors. Here, the incorporation of the fluorinated diluent exhibits a profound impact on the system’s robustness, conferring resistance against electrochemical degradation over thousands of cycles. The reported test results demonstrate remarkable endurance: after 10,000 charge-discharge cycles, the electrode retained over 90% of its initial capacity, showcasing an exceptional combination of durability and performance rarely observed in devices operating at similar voltage thresholds.

The intricate balance achieved between electrode porosity and electrolyte composition is a testament to the deliberate and systematic design approach exemplified by the research teams from Southeast University and Nanjing Normal University. Their collaboration through the Key Laboratory of Energy Thermal Conversion and Control and the Jiangsu Key Laboratory of New Power Batteries fostered a cross-disciplinary synergy pivotal for overcoming the entrenched difficulties in supercapacitor technology. Such integrative research emphasizes the significance of understanding molecular-level interactions alongside macroscopic material design.

At its core, this breakthrough highlights how integrating bio-based materials with advanced chemical engineering can transcend existing limitations in energy storage. The fine-tuned hierarchical carbon framework derived from lignin not only benefits from natural abundance and renewability but also leverages unique nanostructures that conventional synthetic carbons find challenging to replicate. This highlights a burgeoning field where green chemistry intersects with high-performance material science, charting a roadmap toward sustainable yet cutting-edge technological solutions.

From a practical perspective, the ability to reliably store and deploy energy at high voltages with low self-discharge drastically enhances the applicability of supercapacitors across various sectors. Industries ranging from fast-charging electric vehicles, aerospace, and portable electronics to smart power grids stand to gain substantially from such advances. The combination of rapid power delivery, improved energy density, and enhanced cycle life represents a trifecta that addresses many of the current limitations impeding widespread adoption.

Moreover, the approach demonstrated here can inspire further research into other biopolymer-derived materials and electrolyte systems, encouraging a broader exploration of green materials in high-tech applications. The principles of molecular matching and electronic compatibility between electrode pores and solvated ions underscore an emerging focus in electrochemical system design: precision tailoring at the nanoscale to unlock macroscopic gains in efficiency and reliability.

The implications of this research reverberate well beyond supercapacitors. By successfully elevating performance metrics through meticulously designed interfaces, it paves the way for future energy storage devices that combine eco-friendly materials with state-of-the-art electrochemical engineering. This synergy could redefine how the energy storage sector approaches challenges of scalability, sustainability, and integration, particularly as global demands for renewable energy solutions intensify.

In conclusion, the joint effort by Dr. Feng Gong and Dr. Hualin Ye’s teams exemplifies a milestone in supercapacitor technology. By fusing lignin-derived porous carbons with a custom-engineered fluorinated lithium electrolyte, they have demonstrated a high-voltage, low self-discharge electrochemical capacitor that achieves superior energy density and long-term stability. This work not only pushes the envelope of performance but also aligns with the growing imperative to develop sustainable, efficient energy storage technologies that can keep pace with the demands of modern industry and society.

Subject of Research: Electrochemical capacitors (supercapacitors) enhanced by lignin-derived porous carbon electrodes and custom lithium-based electrolytes

Article Title: Lignin-derived hierarchical porous carbons enabling high-voltage electrochemical capacitors with low self-discharge

News Publication Date: 28-Jan-2026

Web References:
https://doi.org/10.1007/s44246-025-00255-z

References:
Zhang, S., Liu, S., Si, S. et al. Lignin-derived hierarchical porous carbons enabling high-voltage electrochemical capacitors with low self-discharge. Carbon Res. 5, 11 (2026).

Image Credits: Shichao Zhang, Shenglin Liu, Suyang Si, Keqi Zeng, Chenxin Cai, Xiangzhou Yuan, Yawen Tang, Feng Gong & Hualin Ye

Keywords

Electrochemistry, Electrocatalysis, Fuel Cells, Porous Materials, Supercapacitors

The study focuses on the comprehensive characterization of SiO₂-doped activated carbon, an area that has garnered significant interest in the quest for better battery materials. The utilization of OPEFB, a byproduct of the palm oil industry, presents an opportunity for resource recovery while simultaneously reducing the environmental impact of waste generated. This sustainable pathway is increasingly vital in a world striving for greener technologies. The research shows that integrating geothermal silica into the carbon matrix can enhance the electrochemical properties of the anodes significantly.

The experimental approach implemented by Triana and colleagues involved varying concentrations of SiO₂ within the activated carbon derived from OPEFB. By systematically altering the doping levels, the research team aimed to optimize the structural and electronic characteristics of the anode materials. This careful manipulation is crucial, as the concentration of dopants can profoundly influence the conductivity and overall performance of the electrodes in a lithium-ion battery setup.

Notably, the structural analysis revealed that the presence of SiO₂ not only improved the surface area of the activated carbon but also enhanced its porosity. These characteristics are essential for battery applications, as they facilitate the movement of lithium ions during charge and discharge cycles. The researchers utilized advanced techniques, including scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherms, to characterize the materials extensively and verify their hypotheses regarding the improved physiochemical properties.

Furthermore, the electrochemical performance assessments demonstrated that the SiO₂-doped activated carbon outperformed its undoped counterpart. The researchers documented significant enhancements in specific capacity and cycling stability, marking a pivotal step in the development of more robust and efficient lithium-ion batteries. The implications of this finding could revolutionize the market for small-scale energy storage solutions, particularly in consumer electronics, where performance and longevity are paramount.

This research also opens avenues for future investigations into the scalability of the production process. As the global shift towards renewable and sustainable energy sources accelerates, finding economically feasible methods to produce advanced battery materials is imperative. Triana and his team have made strides in this direction, potentially setting a benchmark for similar studies focusing on waste-to-energy applications.

In addition to enhancing battery performance, the combination of OPEFB and geothermal silica addresses two critical challenges: waste management and resource scarcity. As more industries seek greener alternatives, researchers are continuously searching for innovative ways to repurpose waste products. Using agricultural residues not only contributes to reducing waste but also adds value to materials that might otherwise be discarded.

Another remarkable aspect of this research includes the potential for other industrial applications of SiO₂-doped activated carbon. Besides serving as an anode material in lithium-ion batteries, this versatile compound could find use in energy storage systems, supercapacitors, and even in the domain of carbon capture technologies. The multifunctionality of such materials is a significant step forward in material science, providing researchers with more tools to tackle various energy-related challenges.

The environmental benefits associated with this research cannot be understated. The palm oil industry, while economically vital in many regions, often faces criticism linked to deforestation and environmental degradation. The innovative approach presented in this study emphasizes a circular economy, where agricultural byproducts are utilized in a creative manner, ultimately reducing the sector’s carbon footprint and paving the way for more sustainable practices.

In conclusion, the work of Triana et al. represents an exciting advancement in the development of SiO₂-doped activated carbon for lithium-ion anodes. Their findings not only enrich the existing body of literature but also encourage future research into sustainable materials and their diverse applications in energy storage. As the quest for greener technologies continues, this study stands out as a promising venture into harnessing waste for sustainable innovation.

In summary, the study highlights the merit of utilizing agricultural waste to produce high-performance materials that contribute significantly to the energy storage domain. With continuous research and development, we can expect to see further breakthroughs that not only highlight material efficiency but also embrace sustainable environmental practices. Researchers hope their work inspires others to explore similar pathways, reinforcing the importance of interdisciplinary collaboration in tackling global challenges related to energy and sustainability.

Subject of Research: SiO₂-doped activated carbon from oil palm empty fruit bunches and geothermal silica for lithium-ion coin cell anodes.

Article Title: Comprehensive characterization of SiO₂-doped activated carbon from OPEFB and geothermal silica with varying concentrations for lithium-ion coin cell anodes.

Article References:

Triana, Y., Pratama, W.D.W., Adiputra, M.B. et al. Comprehensive characterization of SiO₂-doped activated carbon from OPEFB and geothermal silica with varying concentrations for lithium-ion coin cell anodes.
Ionics (2026). https://doi.org/10.1007/s11581-025-06934-6

Image Credits: AI Generated

DOI: 10.1007/s11581-025-06934-6

Keywords: SiO₂-doped activated carbon, lithium-ion batteries, OPEFB, geothermal silica, waste utilization, sustainable energy storage.