WARNV5Coulombic mass-balance is open on 10/12 sweep points (>5% closure error). Check substrate consumption + Q_measured.· Logan-group hygiene check; mass balance fundamentals
WARNV6Mean CE × OLR = 54.5 exceeds empirical Logan-group envelope (≤25). Mass transport limits CE at high loading; prediction may be optimistic.· Cheng & Logan 2011 — empirical envelope
WARNV8Air-cathode + HRT 24h: O₂ crossover should depress CE below ~40% but predicted mean is 54%. Verify cathode + biofilm couples.· Cheng et al. 2006; Logan 2008 textbook §5
Reproducing
Logan BE, Cheng S, Watson V, Estadt G (2007) — Environmental Science & Technology
Graphite fiber brush anodes for increased power production in air-cathode microbial fuel cells
acetate utilization (well-defined substrate; high conversion)
p. 3344
95.0
%
84.8
%
-10.7%
green
Δ-bands per Logan & Regan 2006 lab-to-lab reproducibility envelope: green ≤±25%, amber ±25–50%, red >±50%. Predictions from Butler-Volmer + Ohmic + Tafel closure calibrated against the Logan corpus (regression-tested in butler-volmer-calibration.test.ts).
What we don't know about this paper (6 items)
Peak power is reported PER PROJECTED CATHODE AREA (7 cm² carbon cloth). The paper also cites 73 W/m³ volumetric power density which uses a different denominator — do not mix.
The 1430 mW/m² peak was measured with 50 mM PBS buffer; without buffer, the brush configuration drops to ~600-800 mW/m² (proton diffusion becomes rate-limiting at the cathode). Buffer dependence is not encoded in this preset.
The brush specific surface area (7170 m²/m³) is a manufacturer-reported number for the as-received graphite fiber tow. Biofilm coverage is incomplete in practice (~30-60% surface utilization); the BV map approximates this by treating brush as a multiplier on j0 rather than literal area scaling.
CE = 60% is the paper's reported peak; this varies with external load. At MPP (lower R_ext, higher current draw) CE drops to ~25-40% due to mass-transport limitation. The reported value is the operating-point Logan reports — not the optimum CE.
Internal resistance ~8 Ω in this paper — dramatically lower than Liu & Logan 2004 (~161 Ω) because the brush short-circuits the activation barrier. This is the dominant mechanism, not "more surface area = more biofilm = more power" (a common misreading).
Acetate ≠ wastewater. The 1430 mW/m² number is NOT achievable on real domestic wastewater — Logan-group brush-anode wastewater runs typically peak at 200-500 mW/m² due to the OLR / kinetic complexity of mixed substrates.