High hydrogen production from glycerol or glucose by electrohydrogenesis using microbial electrolysis cells Priscilla A. Selembo a,1 , Joe M. Perez a,2 , Wallis A. Lloyd a,3 , Bruce E. Logan b, * a Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802, USA b Department of Civil and Environmental Engineering, Pennsylvania State University, University Park, PA 16802, USA article info Article history: Received 21 March 2009 Received in revised form 29 April 2009 Accepted 3 May 2009 Available online 31 May 2009 Keywords: MEC Electrohydrogenesis Biocatalyzed electrolysis Hydrogen Glycerol Glucose Biodiesel abstract The use of glycerol for hydrogen gas production was examined via electrohydrogenesis using microbial electrolysis cells (MECs). A hydrogen yield of 3.9 mol-H 2 /mol was obtained using glycerol, which is higher than that possible by fermentation, at relatively high rates of 2.0  0.4 m 3 /m 3 d(E ap ¼ 0.9 V). Under the same conditions, hydrogen was produced from glucose at a yield of 7.2 mol-H 2 /mol and a rate of 1.9  0.3 m 3 /m 3 d. Glycerol was completely removed within 6 h, with 56% of the electrons in intermediates (primarily 1,3-propanediol), with the balance converted to current, intracellular storage products or biomass. Glucose was removed within 5 h, but intermediates (mainly propionate) accounted for only 19% of the electrons. Hydrogen was also produced using the glycerol byproduct of biodiesel fuel production at a rate of 0.41  0.1 m 3 /m 3 d. These results demonstrate that electrohydro- genesis is an effective method for producing hydrogen from either pure glycerol or glycerol byproducts of biodiesel fuel production. ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. 1. Introduction Glycerol is a commodity chemical widely used by the phar- maceutical industry. However, it is being overproduced as a result of biodiesel fuel production as 1 L of glycerol is made for every 10 L of biodiesel fuel produced. At the current annual production capacity of 9.8 billion liters (www.biodiesel.org), 980 million liters of glycerol/yr are produced compared to a demand of only 216 million liters/yr [1]. One alternative use for glycerol is hydrogen gas production by anaerobic fermentation [2–4]. However, only a maximum of 3 mol of H 2 can be produced per mole of glycerol if acetate is the main soluble fermentation end product. Further conver- sion to hydrogen without additional energy is not possible due to an overall endothermic reaction. Hydrogen yields obtained from pure glycerol (P-glycerol) fermentation are often substantially lower than this maximum value, mainly due to formation of 1,3-propanediol (PD), by a reaction which requires hydrogen [5]. Yields obtained during glycerol fermentation were 0.05–0.28 mol-H 2 /mol using mixed cultures [3,5], and 0.61–1.05 mol-H 2 /mol using pure cultures [2,4]. The actual glycerol byproduct from biodiesel (B-glycerol) produced * Corresponding author. Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park, PA 16802, USA. Tel.: þ1 814 863 7908; fax: þ1 814 863 7304. E-mail addresses: pag8@psu.edu (P.A. Selembo), jmp13@psu.edu (J.M. Perez), wal3@psu.edu (W.A. Lloyd), blogan@psu.edu (B.E. Logan). 1 Tel.: þ1 814 865 9387; fax: þ1 814 863 7304. 2 Tel.: þ1 814 865 0340; fax: þ1 814 865 7846. 3 Tel.: þ 1 814 865 0340; fax: þ 1 814 865 7846. Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2009.05.002 international journal of hydrogen energy 34 (2009) 5373–5381