The Development and Maximization of a Novel Photosynthetic Microbial Fuel Cell Using Rhodospirillum rubrum

(1) Century High School, Rochester, Minnesota, (2) Mayo Clinic, Rochester, Minnesota

* These authors made equal contributions
Cover photo for The Development and Maximization of a Novel Photosynthetic Microbial Fuel Cell Using <em>Rhodospirillum rubrum</em>

This study analyzes the potential viability of the photosynthetic bacterium Rhodospirillum rubrum for producing electricity via microbial fuel cell (MFC), as prior research has not investigated this capacity. A prototype for a photoMFC was developed using clear PVC along with carbon cloth and steel electrodes. Initial testing revealed that R. rubrum could produce power utilizing the photoMFC (peak power of approximately 1.25 W/m²). Having established R. rubrum ’s capacity for photoMFC performance, the wavelength of exposed light and resistance were modified to determine the ideal conditions. An analysis of variance (ANOVA) revealed that the differences in power outputs under varied wavelengths were statistically significant (p < 0.0001). Power curves were calculated to determine the optimal resistance via regression analysis (r² = 0.93, p < 0.0001, optimized resistance: 231 Ω). The fuel cell was lastly monitored under sunlight (in a greenhouse) over a 10-day trial, with results showing that the photoMFC could perform effectively under practical outdoor conditions. Under optimal conditions, the R. rubrum photoMFC was predicted to produce maximum instantaneous power of 1.25 W/m². In comparison to other high-power output photoMFCs, the R. rubrum photoMFC performed about 44% as effectively. Although the R. rubrum photoMFC did not perform as efficiently as other reported photoMFCs, its abundance in facilities that invite practical MFC implementation such as wastewater treatment coupled with the fact that R. rubrum is both a heterotrophic and photosynthetic bacteria support its usefulness in realistic, large-scale industrial MFC models.

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