While your local grocery store most likely doesn’t have any tamarinds in its fresh produce aisle, the tropical fruit is consumed in great quantities in Asia, where the fruit’s bulky shells usually end up in landfills after they’ve been discarded.

In a bid to find a better use for this agricultural waste, a team of scientists at Singapore’s Nanyang Technological University (NTU) discovered a way to convert the carbon-rich tamarind shells into carbon nanosheets — ultra-thin layers of carbon that can be used to store energy.

Carbon nanosheets are a key component of supercapacitors (or ultracapacitors)—energy storage devices that are used in applications requiring many rapid charge/discharge cycles. Such applications include electric vehicles that use these ultracapacitors along with batteries for tasks like quickly delivering power during acceleration.

As part of the study, the scientists collected discarded shells from the food industry, washed them, and then dried them at a temperature of 100C (212F) for about six hours. Next, the team ground the dried shells into a powder which they later baked in a furnace, turning the tamarind dust into carbon nanosheets.

Because tamarind shells are porous structures rich in carbon, they increase the carbon nanosheet’s surface area, thus allowing it to store more electricity. According to the scientists, the tamarind shell-derived nanosheets showed good electric conductivity and thermal stability, making them a promising option for energy storage.

Eventually, the novel tamarind-based nanosheets could provide an eco-friendly alternative to their industrially manufactured counterparts when scaled up, while also contributing to a circular economy.