Bioelectricity Generation from Onion Waste

Due to the culinary and medicinal importance of onions, they are widely consumed as a vegetable. Electrogenic microorganisms, commonly found in the environment, are characterised by their ability to generate electricity. Most of these microbes are bacteria and fungi. In this study, bioelectricity was produced from onion waste. The investigation involved isolating and identifying the microorganisms present in the onion waste sample. Additionally, the nutritional content and pH level of the onion waste were analysed. Bioelectricity was generated over 16 days in a microbial fuel cell (MFC) with a copper anode and a zinc cathode. Composting and mixing the samples produced a slurry of onion waste. Microbiological analysis revealed the presence of twelve bacterial species, including Bacillus subtilis, Proteus mirabilis, Micrococcus spp., and Staphylococcus aureus, as well as six fungal species: Alternaria alternata, Aspergillus niger, Penicillium digitatum, and Saccharomyces cerevisiae. The results indicated a high moisture content at the initial stage (90.5%), which is consistent with its nutritional makeup. The pH ranged from 3.0 to 4.3, indicating an acidic environment. The highest voltage, 429 mV, was recorded on the first day, while the maximum current and power density, 2.1 mA and 11 mW/cm2, were observed on the fourth day. These findings suggest that discarded onions could be used to generate power for various applications. Further research is needed to assess the total power output and the duration of the process. Monitoring the continuous production and harvesting of rapidly growing electrogenic microbes could enhance both performance and efficiency.