In this study, the low-strength effluent from an equalization tank of the wastewater treatment plant in a beverage factory was used for the production of hydrogen and methane. The COD concentration of this low-strength wastewater was 2.9 +/- 2.0 g COD/L. In a two-phase anaerobic fermentation system, the hydrogen-producing bioreactor was operated at HRT 8 h, while the methane-producing reactor operated at HRT 24 h. The maximum MPR, methane yield (MY), methane content and COD removal were 72 +/- 31 mL/L-d, 58 +/- 12 mL/g COD, 92 +/- 2% and 78%, respectively. Energy efficiency in this study was calculated as follows, the maximum heating value was 2.2 x 10(8) kcal/y. The annual carbon-emission reduction was 8.8 x 10(4) kg CO2/y, 5.2 x 10(4) kg CO2/y, 7.2 x 10(4) kg CO2/y when energy-equivalent coal, natural gas or fuel was used, respectively. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.