A comparative study of BQ2557 and LTC3108 as efficient ultra-low bioelectricity harvesters from soil microbes using microbial fuel cells

Abstract

Microbial fuel cells (MFCs) are attractive bio-electrochemical transducers that can convert waste and organic substrates into usable energy through the metabolic activity of electroactive microbes. However, the power generated by MFCs is relatively low compared to other types of fuel cells. This poses a serious problem for the practical application of MFCs. Commercially available voltage boosters are not suitable for use with MFCs due to the low current capacity of the MFCs. Therefore, special amplifiers are needed to boost the power of MFCs. In this study, two ultra-low harvesters (BQ25570 and LTC 3108) were configured and tested for their efficiency in extracting usable energy from soil MFCs. The result showed that the BQ could harvest bioelectricity from three MFCs connected in series to charge a 0.22 F supercapacitor up to 3.5 volts, which in turn was used to power a light-emitting diode (LED). The LTC, on the other hand, boosted the voltage of a single MFC from 0.72 V to 3.3 V. The increased voltage was used directly to supply a white LED operating at a constant voltage of 2.5 V. The voltage at the LED remained constant even when the MFC voltage dropped to 20 mV. These results demonstrated the potential of soil microbes to generate free energy that can be harvested, amplified and used for practical applications. Compared to the BQ, the LTC performed better with the soil MFC, boosting the voltage of a single MFC unit to a usable level without the need for a battery or supercapacitor.