This study investigated the effects of pH, temperature and hydraulic retention time (HRT) and organic loading rate (OLR) on hydrogen production from dairy processing waste (DPW) in semi-continuous 60 L pilot induced bed reactors (IBR). Results show pH played a key role on hydrogen production and the optimal pH range was in 4.8-5.5. Digestion under then mophilic temperatures (60 degrees C) had advantages of gaining higher hydrogen yield and suppressing the growth of methanogens. The optimal OLR was 32.9 g-COD/l-d at HRT of 3 days. Under optimal conditions highest hydrogen yield was 160.7 mug-COD removed with 44.6% COD removal. Two-stage digestions demonstrated more energy gain from methane production and further COD removal. The overall gas production in two-stage digestion was 71.7 ml hydrogen and 61.0 ml methane per gram DPW COD. The overall COD removal under optimal conditions was 88.2%. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.