An international consortium of scientists has discovered a novel way to convert tamarind shells into an energy source for vehicles.
Tamarind is a tropical fruit enjoyed worldwide; however, tamarind shells are disposed of during the production process. This agricultural waste is bulky and takes up space in landfills, adding to environmental concerns.
Now, an international team of researchers led by Nanyang Technological University, Singapore (NTU Singapore), have discovered a way to mitigate this environmental issue and put the tamarind shells to good use.
The innovative research was published in the peer-reviewed scientific journal Chemosphere in June.
Carbon Carbon–rich tamarind shells
Tamarind shells are naturally abundant in carbon, and by processing it, the researchers were able to convert the waste material into carbon nanosheets, which are a crucial element necessary for supercapacitors – energy storage devices with a plethora of applications, such as cars, buses, electric vehicles, trains, and lifts.
The consortium – composed of scientists from NTU Singapore, as well as the Western Norway University of Applied Sciences in Norway, and Alagappa University in India – is confident that when scaled up, the nanosheets could present an environmentally friendly replacement to industrially produced nanosheets, as well as cutting down waste in the process.
Study lead, Assistant Professor Cuong Dang, of NTU’s School of Electrical and Electronic Engineering, explained: “Through a series of analysis, we found that the performance of our tamarind shell-derived nanosheets was comparable to their industrially made counterparts in terms of porous structure and electrochemical properties. The process to make the nanosheets is also the standard method to produce active carbon nanosheets.”
Professor G. Ravi, Head, Department of Physics, who co-authored the study with Asst Prof Dr R. Yuvakkumar, who are both from Alagappa University, said: “The use of tamarind shells may reduce the amount of space required for landfills, especially in regions in Asia such as India, one of the world’s largest producers of tamarind, which is also grappling with waste disposal issues.”
Carbon nanosheets for energy storage devices
Tamarind shells are abundant in carbon and permeable in nature, meaning they are an ideal material from which to manufacture carbon nanosheets.
In order to produce the carbon nanosheets, the team began by washing tamarind fruit shells and drying them at 100°C for approximately six hours, and then proceeding to grind them into powder.
Following this, they baked the powder in a furnace for 150 minutes at temperatures between 700 and 900°C, with oxygen deficiency, to convert them into ultrathin sheets of carbon known as nanosheets.
Currently, carbon nanosheets are generally produced by industrial hemp fibres. However, they must be heated at over 180°C for 24 hours, which is four times longer than that of tamarind shells, and at a higher temperature. As well as this, the hemp must be additionally exposed to intense heat to convert them into carbon nanosheets.
The tamarind shell-derived nanosheets also exhibited good thermal stability and electric conductivity, making them promising alternatives for energy storage devices.
Professor Dhayalan Velauthapillai, Head of the research group for Advanced Nanomaterials for Clean Energy and Health Applications at Western Norway University of Applied Sciences, who participated in the study, added: “Carbon nanosheets comprise of layers of carbon atoms arranged in interconnecting hexagons, like a honeycomb. The secret behind their energy energy–storing capabilities lies in their porous structure leading to a large surface area which helps the material to store large amounts of electric charges.
Going forward, the scientists are hoping to investigate larger larger–scale production of the carbon nanosheets with agricultural partners. They are also working to lessen the amount of energy required for the production process, making it more environmentally friendly, and are seeking to enhance the electrochemical properties of the nanosheets.
The group also wishes to investigate the possibility of employing different types of fruit skins or shells to produce carbon nanosheets.