Every year, the world generates approximately eight million tons of discarded cigarette butts. This massive volume of waste, primarily made of cellulose and cellulose acetate, is notoriously difficult to break down and contains harmful substances like heavy metals and volatile organic compounds. However, a recent study published in the journal Energy & Environment Nexus by Jieni Wang, Chenlin Wei, Haodong Hou, Fangfang Zhang, Chenxiao Liu, Leichang Cao, Shicheng Zhang, Jinglai Zhang, and James H. Clark highlights a promising way to recycle this waste. The researchers successfully converted these cigarette butts into a specialized type of porous biochar that can be used in supercapacitors, which are devices that store and release electrical energy very quickly.

The researchers used a two-step process involving heat and chemical treatment to create what they call nitrogen and oxygen co-doped hierarchical nanoporous biochars. By adjusting the temperatures and the amount of activator used, they were able to create a material with a highly organized pore structure. The best version of this material was produced at a temperature of 700 degrees Celsius. This specific version, named CNPB-700-4, possesses a remarkably high specific surface area of 2,133.5 square meters per gram. This massive surface area is crucial because it allows more ions from the electrolyte to interact with the electrode, leading to better energy storage.

When tested as an electrode in a supercapacitor, this cigarette-derived material showed excellent performance. It achieved an energy storage capacity, known as capacitance, of 344.91 farads per gram at a standard current density. The study also found that the material is incredibly stable over time. After ten thousand constant charge and discharge cycles, the material retained 95.44 percent of its original capacity, representing a loss of less than five percent. This level of durability is essential for any material intended for commercial energy storage applications, where devices must last for years without significant performance drops.

The effectiveness of the material comes from both its physical structure and its chemical makeup. The porous structure includes a mix of tiny micropores and slightly larger mesopores. The micropores are excellent for storing charge, while the mesopores act like highways, allowing the electrolyte to move quickly in and out of the material. Additionally, the researchers successfully “doped” the biochar with nitrogen and oxygen. These elements create active sites on the surface of the carbon that trigger additional chemical reactions, further boosting the amount of energy the device can store.

This research demonstrates that turning a common and problematic waste product into a high-value material for green energy technology is both possible and efficient. The resulting supercapacitors have an energy density of 24.33 watt-hours per kilogram and a power density of 373.71 watts per kilogram. These figures suggest that the material has high commercial potential. By finding a valuable use for cigarette butts, this study addresses both the need for better energy storage solutions and the urgent requirement for more sustainable waste management practices worldwide.

Source: Wang, J., Wei, C., Hou, H., Zhang, F., Liu, C., Cao, L., Zhang, S., Zhang, J., & Clark, J. H. (2026). N,O co-doped hierarchical nanoporous biochar derived from waste cigarette butts for high-performance energy-storage application. Energy & Environment Nexus, 2, e001.