Performance of scalable air-cathode microbial fuel cell (MFC) of 26 L volume, made from clayware cylinder with multiple electrodes, was evaluated. When electrodes were connected in parallel with 100 Omega resistance (R-ext), power of 11.46 mW was produced which was 4.48 and 3.73 times higher than individual electrode pair and series connection, respectively. Coulombic efficiency of 5.10 +/- 0.13% and chemical oxygen demand (COD) removal of 78.8 +/- 5.52% was observed at R-ext of 3 O. Performance under different organic loading rates (OLRs) varying from 0.75 to 6.0 g COD L-1 d(-1) revealed power of 17.85 mW (47.28 mA current) at OLR of 3.0 g COD L-1 d(-1). Internal resistance (R-int) of 5.2 Omega observed is among the least value reported in literature. Long term operational stability (14 months) demonstrates the technical viability of clayware MFC for practical applications and potential benefits towards wastewater treatment and electricity recovery. (C) 2015 Elsevier Ltd. All rights reserved.