ShareFruit waste being used to generate electricity for lighting in new circular economy study
Waste reduction, whether in a manufacturing or a construction environment is moving ahead in leaps and bounds with new and exciting developments announced almost weekly. In the latest waste reduction and circular economy study, researchers from the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois Urbana-Champaign, USA have successfully used waste pomelo peel biomass to develop nanogenerators that can power small electric devices and monitor biomechanical motions.
Waste reduction, whether in a manufacturing or a construction environment is moving ahead in leaps and bounds with new and exciting developments announced almost weekly. In the latest waste reduction and circular economy study, researchers from the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois Urbana-Champaign, USA have successfully used waste pomelo peel biomass to develop nanogenerators that can power small electric devices and monitor biomechanical motions.
Also known as a shaddock, it is the largest citrus fruit and commonly grown in Asia, the pomelo fruit has a very thick peel, which is typically discarded, resulting in a considerable amount of food waste. A pomelo fruit typically weighs 1-2 kilograms with the peel accounting for up to 50% of the total weight. In the study, the peel was separated from the fruit and the thin outer layer of the peel was removed. The remaining thick, spongy white peel was cut into smaller pieces and freeze dried to preserve its unique three-dimensional, porous structure, and then stored under different humidity conditions.
After the peel’s chemical and mechanical properties were analysed, it was used to create devices that can convert mechanical energy into electricity and serve as self-powered motion sensors.
According to study co-author Yi-Cheng Wang, an assistant professor in the Department of Food Science and Human Nutrition, part of the College of Agricultural, Consumer and Environmental Sciences at Illinois, pomelo peel can be upcycled to higher-value products instead of being discarded, while mitigating the negative impacts of food and agricultural waste.
Elaborating on the pomelo peel study, Wang says that the devices leverage the principle of contact electrification, similar to what one experiences in winter when touching a doorknob and feeling a shock, for instance.
“The fundamental mechanism is contact electrification, or triboelectrification – ‘tribo’ means rubbing. When two materials are rubbed against each other, static electricity can form due to the transfer of charges between them. We wanted to explore if we could collect and utilise that electricity,” Wang says.
The researchers used pomelo peel biomass and a plastic (polyimide) film as two triboelectric layers that are brought into contact when external force is present. A copper-foil electrode was attached to each of these layers to assess how well the resulting device could convert external mechanical energy into electricity.
By simply tapping the pomelo peel-based triboelectric nanogenerator with a finger, they could light up about 20 LEDs. The study demonstrated that a calculator or sports watch could be powered solely by these mechanical forces without needing an external power source, when the device is integrated with a power management system incorporating energy storage.
“This application has strong potential to convert otherwise wasted energy into useful electricity. We also found that, thanks to pomelo peel’s naturally porous structure, triboelectric devices based on it can be highly sensitive to force and force frequency. This inspired us to develop sensing devices that can be attached to the human body for biomechanical monitoring,” Wang says.
The proof-of-concept sensors, when attached to various body parts, were able to monitor biomechanical movement such as joint motions and gait patterns. The movements of different body parts can lead to contact electrification between the triboelectric layers, generating distinct electrical signals corresponding to different motions.
“This work highlights exciting opportunities to transform food waste into value-added devices and materials. By potentially replacing or supplementing non-renewable counterparts and reducing waste, it could contribute significantly towards long-term sustainability, and we will continue exploring more opportunities for upcycling food and agricultural waste,” Wang says.
The researchers have filed a provisional patent for their pomelo peel-based triboelectric devices.
The paper, “Valorization of Food Waste: Utilizing Natural Porous Materials Derived from Pomelo-Peel Biomass to Develop Triboelectric Nanogenerators for Energy Harvesting and Self-Powered Sensing”, is published in ACS Applied Materials & Interfaces [DOI: 10.1021/acsami.4c02319].
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