Palm oil mill effluent (POME) is a potential source for biohydrogen. A continuous stirred tank reactor was used to study the effects of mixing speeds of a Rushton turbine on the biohydrogen production. The initial organic loading rate and volatile solids of influent were 55 g of chemical oxygen demand per liter of influent per day and 30.28 g of volatile solids per liter of influent, respectively. The retention time was 24 h and the turbine speeds were 10, 50, 100, and 150 rpm. The corresponding hydrogen yields were 2,669, 2,868, 3,413, and 3479 mL per liter of influent. The total maximum hydrogen yield at 150 rpm was equivalent to 6958 mL per liter of POME. A speed of 100 rpm was recommended for the constant speed operation as it gave the highest net energy gain of 23.96 kJ L-POMS(-1) Five varying speed schemes were studied to determine the maximum net energy gain. The varying speed schedule should be 100 rpm for the first 8 h and 10 rpm for the rest 16 h, which increased the net energy gain by 11% in comparison to the 100 rpm constant mixing speed. Feasibility analysis revealed possibility in industrial application. (C) 2019 Published by Elsevier Ltd.