초록
A two-step, un-coupled process producing hydrogen (H<SUB>2</SUB>) from wheat straw using Caldicellulosiruptor saccharolyticus in a 'Continuously stirred tank reactor' (CSTR) followed by anaerobic digestion of its effluent to produce methane (CH<SUB>4</SUB>) was investigated. C. saccharolyticus was able to convert wheat straw hydrolysate to hydrogen at maximum production rate of approximately 5.2 L H<SUB>2</SUB>/L/Day. The organic compounds in the effluent collected from the CSTR were successfully converted to CH<SUB>4</SUB> through anaerobic digestion performed in an 'Up-flow anaerobic sludge bioreactor' (UASB) reactor at a maximum production rate of 2.6 L CH<SUB>4</SUB>/L/day. The maximum energy output of the process (10.9 kJ/g of straw) was about 57% of the total energy, and 67% of the energy contributed by the sugar fraction, contained in the wheat straw. Sparging the hydrogenogenic CSTR with the flue gas of the UASB reactor ((60% v/v) CH<SUB>4</SUB> and (40% v/v) CO<SUB>2</SUB>) decreased the H<SUB>2</SUB> production rate by 44%, which was due to the significant presence of CO<SUB>2</SUB>. The presence of CH<SUB>4</SUB> alone, like N<SUB>2</SUB>, was indifferent to growth and H<SUB>2</SUB> production by C. saccharolyticus. Hence, sparging with upgraded CH<SUB>4</SUB> would guarantee successful hydrogen production from lignocellulosic biomass prior to anaerobic digestion and thus, reasonably high conversion efficiency can be achieved.