Production of Hydrogen from Glucose as a Biomass Simulant: Integrated Biological and Thermochemical Approach Sadashiv M. Swami, † Vaibhav Chaudhari, † Dong-Shik Kim, † Sang Jun Sim, ‡ and Martin A. Abraham* ,† Department of Chemical and EnVironmental Engineering, UniVersity of Toledo, Toledo, Ohio 43606, and Department of Chemical Engineering, Sungkyunkwan UniVersity, Suwon, 440-746, Korea Hydrogen production from biomass was investigated using an integrated biological and thermochemical process. Glucose was used as a biomass surrogate and was first converted to ethanol in a fermentation process. The fermentation experiments were carried out using Saccharomyces cereVisiae. The fermentation broth was then used in aqueous phase reforming (APR) over a platinum-based catalyst. An economic analysis of the proposed process demonstrates the economic viability of producing hydrogen from biomass using fermentation combined with APR. The average production yield of hydrogen was ∼25%. The hydrogen obtained from APR of the fermentation broth was compared against the yield from a feed containing 5% ethanol in water. While the catalyst was stable for an extended time on stream during APR of ethanol, very rapid deactivation was observed during APR of fermentation broth. Different catalyst characterization techniques, including XRD, BET surface area, and ICP-AES, were employed to investigate the causes of catalyst deactivation. Although the analysis suggested similar catalyst changes in both cases, and the exact deactivation mechanism could not be concluded, these techniques helped to eliminate some mechanisms while suggesting other possible deactivation routes. Nanofiltration of the fermentation broth was shown to remove the impurities leading to deactivation. Introduction Hydrogen is receiving increased attention as a future energy alternative owing to the recent global efforts to reduce the dependence on fossil fuels and the desire to reduce carbon- based emissions. Hydrogen offers great potential as a clean renewable energy carrier. It has the highest gravimetric energy density of any known fuel, and it can be used in a fuel cell with a high energy conversion efficiency compared to other electrochemical and combustion processes. As fuel cells are becoming more efficient and approaching commercialization, hydrogen will become an important component of the alternative energy profile. Despite its tremendous potential, hydrogen energy has many technical challenges. One of them is the production of sufficient quantities of hydrogen. 1 There are many ways to produce hydrogen including steam reforming or thermal cracking of natural gas, coal gasification, electrolysis, and biological production. Currently, nearly 90% of hydrogen is produced by the steam reforming of natural gas and light oil fractions. 2 These methods consume fossil fuel, and thus fail to address either the long-term reliance on fossil resources or the carbon emissions issues associated with their consumption. Direct biological hydrogen production can be classified into biophotolysis using algae and cyanobacteria, photodecomposi- tion by photosynthetic bacteria, fermentation, and hybrid systems using photosynthetic decomposition combined with fermenta- tion. 3-5 The major problems in the biological hydrogen produc- tion are slow reaction rates and the problems associated with scale-up of bioreactors. 6 Also, even if most nonphotosynthetic anaerobic bacteria use glucose to produce hydrogen, 7 usually the resulting components after hydrolysis of biomass wastes consist of various sugars including arabinose and xylose as well as glucose, which are not well utilized by anaerobic bacteria. Because hydrogen is not produced through biological pro- cesses in sufficient yield to operate commercial size fuel cells, biohydrogen technologies still need further progress. 8 Thus, combinations of other well-established techniques have been tested to overcome their limitations. Direct conversion of biomass to hydrogen has been extensively studied in the past few years. The most common techniques for biomass conversion are gasification and pyrolysis. 9 However, the major disadvantage of these processes is the decomposition of the biomass feed stock, leading to char and tar formation. 10,11 Overcoming this difficulty, aqueous phase reforming (APR) has been demon- strated as an alternative technique for hydrogen production from sugars. 12 In order to reduce the char formation and enhance the biomass conversion, it has been suggested that the biomass feedstock be converted to organic chemicals before reforming. In previous work, researchers first reduced glucose to sucrose through hydrogenation, before APR. 13 As an alternative, we have proposed an integrated fermentation and reforming process. APR has been chosen over conventional steam or autothermal reforming so that unconverted biomass from a fermentation process can still be utilized in a reforming process without decomposition. Biomass feedstock will be first converted to ethanol and organic acids in a fermentation process followed by aqueous phase reforming of these converted products to hydrogen. The integrated biological and reforming process concept is depicted in Figure 1, in which conventional conversion processes based on fermentation and catalytic reforming are combined to convert waste biomass into hydrogen. Biomass wastes from food or agricultural processing can be converted, nearly eliminating the cost of raw materials (or even possibly generating revenue by reducing waste disposal related costs) and improving the overall economics of the process. In order to be a practical option for industrial and agricultural interests, an economically * To whom correspondence should be addressed. Tel.: (419) 530- 8092. E-mail: martin.abraham@utoledo.edu. † University of Toledo. ‡ Sungkyunkwan University. 3645 Ind. Eng. Chem. Res. 2008, 47, 3645-3651 10.1021/ie070895p CCC: $40.75 © 2008 American Chemical Society Published on Web 12/14/2007