TY - JOUR
T1 - Evaluation of energy-conversion efficiencies in microbial fuel cells (MFCs) utilizing fermentable and non-fermentable substrates
AU - Lee, Hyung Sool
AU - Parameswaran, Prathap
AU - Marcus, Andrew
AU - Torres, Cesar
AU - Rittmann, Bruce
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2008/3
Y1 - 2008/3
N2 - We established the first complete electron-equivalent balances in microbial fuel cells (MFCs) fed with non-fermentable (acetate) and fermentable (glucose) electron donors by experimentally quantifying current, biomass, residual organic compounds, H2, and CH4 gas. The comparison of the two donors allowed us to objectively evaluate the diversion of electron flow to non-electricity sinks for fermentable donors, leading to different behaviors in energy-conversion efficiency (ECE) and potential efficiency (PE). Electrical current was the most significant electron sink in both MFCs, being 71% and 49%, respectively, of the initial COD applied. Biomass and residual organic compounds, the second and third greatest sinks, respectively, were greater in the glucose-fed MFC than in the acetate-fed MFC. We detected methane gas only in the glucose-fed MFC, and this means that anode-respiring bacteria (ARB) could out-compete acetoclastic methanogens. The ECE was 42% with acetate, but was only 3% with glucose. The very low ECE for glucose was mostly due to a large increase of the anode potential, giving a PE of only 6%. Although the glucose-fed MFC had the higher biomass density on its anode, it had a very low current density, which supports the fact that the density of ARB was very low. This led to slow kinetics for electron transfer to the anode and accentuated loss due to the substrate-concentration gradient in the anode-biofilm. The large drop of PE with low current, probably caused by a low ARB density and electron (e-) donor concentration, resulted in a poor maximum power density (9.8 mW/m2) with glucose. In contrast, PE reached 59% along with high current for acetate and the maximum power density was 360 mW/m2.
AB - We established the first complete electron-equivalent balances in microbial fuel cells (MFCs) fed with non-fermentable (acetate) and fermentable (glucose) electron donors by experimentally quantifying current, biomass, residual organic compounds, H2, and CH4 gas. The comparison of the two donors allowed us to objectively evaluate the diversion of electron flow to non-electricity sinks for fermentable donors, leading to different behaviors in energy-conversion efficiency (ECE) and potential efficiency (PE). Electrical current was the most significant electron sink in both MFCs, being 71% and 49%, respectively, of the initial COD applied. Biomass and residual organic compounds, the second and third greatest sinks, respectively, were greater in the glucose-fed MFC than in the acetate-fed MFC. We detected methane gas only in the glucose-fed MFC, and this means that anode-respiring bacteria (ARB) could out-compete acetoclastic methanogens. The ECE was 42% with acetate, but was only 3% with glucose. The very low ECE for glucose was mostly due to a large increase of the anode potential, giving a PE of only 6%. Although the glucose-fed MFC had the higher biomass density on its anode, it had a very low current density, which supports the fact that the density of ARB was very low. This led to slow kinetics for electron transfer to the anode and accentuated loss due to the substrate-concentration gradient in the anode-biofilm. The large drop of PE with low current, probably caused by a low ARB density and electron (e-) donor concentration, resulted in a poor maximum power density (9.8 mW/m2) with glucose. In contrast, PE reached 59% along with high current for acetate and the maximum power density was 360 mW/m2.
KW - ARB density
KW - Concentration gradient
KW - Electron-equivalent balance
KW - Energy-conversion efficiency
KW - Potential efficiency
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U2 - 10.1016/j.watres.2007.10.036
DO - 10.1016/j.watres.2007.10.036
M3 - Article
C2 - 18035391
AN - SCOPUS:40749115223
SN - 0043-1354
VL - 42
SP - 1501
EP - 1510
JO - Water Research
JF - Water Research
IS - 6-7
ER -