Two-stage thermophilic solid state anaerobic digestion (SS-AD) processes for biohythane production from Chlorella sp. biomass was investigated. The hydrogen and methane yield from fresh Chlorella sp. biomass was 124.9 mL H-2 gVS(-1) and 230.1 mL CH4 gVS(-1), respectively, at 16% TS with biodegradation efficiency of 34%. Hydrogen and methane production from hydrothermal pretreated Chlorella sp. biomass was 190.0 mL H-2 gVS(-1) and 319.8 mL CH4 gVS(-)1, respectively at 16% TS with biodegradation efficiency of 47%. Pretreatment of Chlorella sp. biomass with hydrothermal follow by two-stage thermophilic SS-AD improved 150% biogas production comparing with fresh biomass. Clostridium sp. was the main bacteria responsible for hydrogen production. Clostridium sp. and Ruminococcus sp. was main bacteria in methane stage, while Methanoculleus sp. and Methanothermobacter sp. was dominated archaea in methane production process. Chlorella sp. biomass with hydrothermal pretreatment has great potential for hydrogen and methane production via two-stage thermophilic SS-AD. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.