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Table 2 MFC voltage (mV), current density (A/m2) and power density (mW/m2) after adding humic acids as additional electron carriers with a MFC with a small cathode (surface area is 50 × 10−6 m2)

From: Electron carriers increase electricity production in methane microbial fuel cells that reverse methanogenesis

MFC reactor Voltage (mV) Current density (A/m2) Fold change Power density (mW/m2) Fold change
Base case #1 670 ± 60 0.10 ± 0.01 1 68 ± 6 1
Base case #2 721.5 ± 0.7 0.6 ± 0.1 6 450 ± 90 7
Base case #2 + humic acids (total 0.5%) 712 ± 4 2.1 ± 0.4 21 1400 ± 200 21
Base case #2 + humic acids (total 3.3%) 750 ± 60 6 ± 1 60 4700 ± 800 69
Base case #2 + cytochrome C from S. cerevisiae (20 µM) 732 ± 2 0.97 ± 0.07 10 710 ± 40 10
  1. The base case #1 is M. acetivorans AA/pES1MAT mcr3 (“M. acetivorans”) and G. sulfurreducens was added first followed by sludge once the voltage was below 150 mV and using 38-mm-diameter cathode electrode (surface area is 0.00227 m2). The base case #2 consists of G. sulfurreducens added at the start followed by the addition of sludge + M. acetivorans AA/pES1MAT mcr3 once the voltage was reduced below 150 mV and using a small cathode electrode (surface area is 50 × 10−6 m2). The additional electron carriers (humic acids) were added after obtaining the first maximum voltage; 0.5% humic acids were added after 7–8 days and 3.3% humic acids were added after 13–14 days of adding sludge and M. acetivorans. Cytochrome C from S. cerevisiae (20 µM) was added as an additional electron carrier after obtaining the first maximum in voltage after adding sludge and M. acetivorans AA/pES1MAT mcr3. The external resistance was 1000 Ohm