Hybrid Microbial-Photosynthetic Biofuel Cells for Simultaneous Bacterial Glycerol Biotransformation and Algal Carbon Dioxide Capture

Camilo Enrique La Rotta Hernández,Galba Maria De Campos Takaki,Patricia Virginia Dantas,Maria De Los Angeles Perez,Sergio Peres Ramos,Ady Luna Leite

doi:10.5935/0103-5053.20140032

Abstract

Power generation at bioanodes of Pseudomonas aeruginosa for glycerol biotransformation was coupled to the carbon dioxide capture in biocathodes of Chlorella vulgaris in hybrid photosynthetic biofuel cells (HPSBC). Biochemical parameters such as microbial growth, substrate consumption, production of bacterial pigments and CO2 capture were studied. Also electrochemical parameters of maxima current densities (Idmax), power output (Pdmax) and coulombic efficiencies (CE) were studied. Initially, both systems were evaluated in separate against the corresponding Fe3+|Fe2+ redox pair. In bacterial systems, important results in terms of Idmax of 42 ± 2.1 µA cm-2, CE of 48 ± 2.4% and Pdmax of 350 ± 17.5 mW cm-2 were achieved. Likewise, for isolated algal cathode systems, Idmax of 93 ± 4.65 µA cm-2, CE of 56 ± 2.8% and Pdmax of 3.2 ± 0.16 mW cm-2, were achieved. In contrast, when both systems were coupled, a lower Idmax of 48.5 ± 2.42 µA cm-2 was observed. Finally, bioelectrochemical conditions were improved based on substrate consumption, electrogenic products, cation transport and mediated electron transfer systems. Thus, higher average values for Idmax of 80 ± 4.0 µA cm-2, CE of 71.5 ± 3.57% and Pdmax of 650 ± 32.5 mW cm-2 were obtained.

Highlights

The search for alternative sources of renewable energy with low environmental impact has been the major concern in recent years due to the availability of sources with higher energy densities, which, nowadays are obtained mainly from fossil fuels
The use of a chemical catholyte or metal catalyst requires the physical separation of the anode and cathode chambers by an ion exchange membrane (IEM) to prevent substrate diffusion from the anode to the cathode that leads to a rapid deactivation of the cathode and deterioration of Microbial fuel cells (MFC) performance IEM inhibits substrate diffusion but permits proton migration from the anode to the cathode
In spite of the detrimental effect that ferro- and ferricyanide can cause on the microbial electrodes, their use together with the saline bridges continues to be the best choice, instead of using the highly priced proton exchange membrane (PEM) systems and expensive electrodes based on rare metals.[36]

Summary

Introduction

The search for alternative sources of renewable energy with low environmental impact has been the major concern in recent years due to the availability of sources with higher energy densities, which, nowadays are obtained mainly from fossil fuels. After 100 h of process, the CO2 depletion caused a rapid decrease in Id. Figure 4 shows the control experiments that were performed to determine the effect that the illuminated algal cultures caused on the chronoamperometric profiles without aeration and the effect of free cell media supplemented with air or pure CO2.

Results

Conclusion