Effect of temperature and temperature shock on the stability of continuous cellulosic-hydrogen fermentation

•The 55±1 and 80±1°C presented long-term stable cellulosic-hydrogen fermentation.•The first study on the effect of temperature shock on bioH2 production of cellulose.•The reactor under 55 or 80°C appeared to be more resilient to the shock than 37°C.•The recovery period after the 2nd shock was shorter than after the 1st shock. Three continuous stirred tank reactors (CSTR) were operated under mesophilic (37±1°C), thermophilic (55±1°C) and hyper-thermophilic (80±1°C) temperatures for 164days to investigate the effect of temperature and temperature shock on the cellulosic-dark hydrogen fermentation by mixed microflora. During steady state condition, the sudden decreases in the fermentation temperature occurred twice in each condition for 24h. The results show that the 55±1 and 80±1°C presented stable hydrogen yields of 12.28 and 9.72mmol/g cellulose, respectively. However, the 37±1°C presented low hydrogen yield of 3.56mmol/g cellulose and methane yield of 5.4mmol/g cellulose. The reactor performance under 55±1 or 80±1°C appeared to be more resilient to the sudden decreases in the fermentation temperature than 37±1°C. The experimental analysis results indicated that the changing in soluble by-products could explain the effect of temperature and temperature shock, and the thermophilic temperature is expected having a better economic performance for cellulosic-hydrogen fermentation.