WITH PEM (Nafion 117), domestic wastewater feed — comparison run showing the PEM penalty
p. 4042, Table 1
28.0
mW/m²
27.7
mW/m²
-1.1%
green
Power density
without PEM, acetate feed (defined substrate, higher than wastewater) — best-case headline
p. 4043, Table 1
262
mW/m²
272
mW/m²
+3.9%
green
Coulombic efficiency
without PEM, wastewater feed (typical Logan-group mixed-community air-cathode CE)
p. 4043
12.0
%
12.8
%
+6.7%
green
COD removal
COD removal after fed-batch cycle, wastewater feed
p. 4043
80.0
%
81.8
%
+2.2%
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)
The paper reports four configurations (acetate × wastewater) × (with PEM × without PEM); this preset models the "without PEM, wastewater" headline case. The acetate run reaches 262 mW/m² and the with-PEM-wastewater run only 28 mW/m² — both encoded in reportedResults for comparison.
Several setup details are unreported in the 2004 paper: exact buffer composition (the wastewater run used the wastewater's native buffer, not a phosphate buffer), electrode pre-treatment protocol, cathode binder composition. We use Logan-group typical values as the canonical guess.
The often-cited "766 mW/m²" figure is from FOLLOW-UP Logan-group papers (Cheng et al. 2006 with cloth electrode treatment; Cheng & Logan 2007 with NH₃ treatment), NOT from this 2004 paper. The 2004 paper's actual headline is 146 mW/m² wastewater / 262 mW/m² acetate. We encode the original number, not the later optimization.
Reported peak was at a single time point in a fed-batch cycle; lab-to-lab variability on identical Liu-Logan-style single-chamber air-cathode MFCs runs ±30-50% (Logan & Regan 2006).
2004 was 2 years BEFORE the Logan group published the standardized MFC methodology paper (Logan & Regan 2006). Some 2004-paper numbers would be reported differently under the modern reporting convention (e.g., projected vs total cathode area, OCV vs operating voltage normalization). The polarization-curve methodology is robust; the per-condition numbers should be treated as ±20% bounded.
Internal resistance R_int for this configuration is reported as ~84 Ω with PEM and ~161 Ω without PEM — but note the WITHOUT-PEM total resistance is dominated by cathode overpotential, not ohmic loss. The "R_int dropped by removing PEM" narrative refers to the OHMIC component, not total R_int. (Common misreading of the paper.)