Thermophilic consolidated bioprocessing for sustainable hydrogen production
Tuesday, April 29, 2014
Exhibit/Poster Hall, lower level (Hilton Clearwater Beach)
Lew P. Christopher, Center for Bioprocessing Research & Development, South Dakota School of Mines &Technology, Rapid City, SD
Hydrogen (H2) is considered the “energy of the future” due to its non-polluting nature and high energy content (143 MJ/Kg) which is 3.3-fold higher than that of gasoline. An economically-viable, large-scale production of bio-H2 would require development of advanced H2-producing technologies like Consolidated Bioprocessing (CBP). CBP has been proposed as the most cost-efficient and ultimate industrial configuration for low-cost hydrolysis and fermentation of cellulosic biomass with average cost saving of 50%. CBP of lignocellulosic feedstock for H2 production using thermophiles offers several techno-economic advantages: increased conversion rates due to improved mass transfer rates, substrate accessibility and solubility at elevated temperatures; favorable thermodynamics of stochiometric H2 yields at higher temperatures; diminished possibility of contamination by unwanted microorganisms; reduced formation of by-products. The CBP H2 production capabilities of the extreme thermophile Caldicellulosiruptor saccharolyticus DSM 8903 were examined on switchgrass (SWG) and municipal solid waste (MSW), with glucose and microcrystalline cellulose (MCC) serving as references. H2 production from glucose reached the theoretical maximum for dark fermentation of 4 mol H2/mol glucose. The H2 yield on MCC, SWG and MSW peaked at 9.4, 11.2, and 3.3 mmol H2/g substrate, respectively. C. saccharolyticus was able to produce H2 from mechanically-comminuted SWG directly without any physicochemical or biological pretreatment. As pretreatment is the single most cost-intensive processing step in biomass bioconversion (25% of total costs on average), combining four processing steps (pretreatment, enzyme production, saccharification, fermentation) into a single biorefinery operation makes C. saccharolyticus a promising CBP candidate for cost-efficient, environmentally-friendly and sustainable production of H2.