Psychrophilic (15 degrees C) and mesophilic (35 degrees C) reactor performance and microbial community dynamics were compared when the biogas fermenters were performed at high altitude and solid state condition using animal manure and highland barley straw as substrate. Longer biogas fermentation time, higher peak methane content and lower volatile fatty acids (VFA) accumulation were found at psychrophilic condition compared to that of at mesophilic condition although the biogas production in both temperature conditions was similar. The cumulative biogas production at 35 degrees C and 15 degrees C were 246 (+/- 5) and 225 (+/- 7) mug volatile solids, respectively. The highest total VFA concentration under 35 degrees C was 10,796 (+/- 310) mg/kg total solid, while it only reached to 2346 (+/- 87) mg/kg total solid at the condition of 15 degrees C. Additionally, the variation of pH, soluble chemical oxygen demand and total ammonia nitrogen during the anaerobic digestion under psychrophilic condition were much smaller than that of under mesophilic condition. Polymerase chain reaction and denaturing gradient gel electrophoresis analysis followed by 16S rDNA sequencing showed that bacteria of genera Bacillus and Clostridium and archaea of genera Methanosarcina and Methanosaeta played a pivotal role during the biogas production. (C) 2017, The Society for Biotechnology, Japan. All rights reserved.