Biohydrogen (H-2) production from dark fermentation processes is inhibited at low culture pH (<4.0). This work investigated the culture pH and H-2 production stability during the dark fermentation of cheese whey, supplemented with buffalo manure. The co-fermentation of cheese whey, rich in high carbohydrate but yielding acidic pH, with buffalo manure characterized by a high alkalinity, is promising for continuous H-2 production in dark fermentation. At a cheese whey to buffalo manure ratio of 4 g VS/g VS, a maximum H-2 yield and production rate of respectively, 152.2 (+/- 43.9) mL H-2/g VS and 215.4 (+/- 62.1) mL H-2/L/d, were achieved at an organic loading rate of 2.1 g VS/L/d of cheese whey at a stable culture pH of 4.8-5.0. The use of buffalo manure improved the H-2 production stability and could replace chemical buffering agents of scaled-up dark fermentation applications. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.