Y.-H. Percival Zhang1, Barbara R. Evans2, Jonathan R. Mielenz3, Robert C. Hopkins4, and Michael W.W. Adams4. (1) Biological Systems Engineering Department, Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech University, 210-A Seitz Hall, Blacksburg, VA 24061, (2) Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, (3) Bioconversion Science and Technology, Oak Ridge National Laboratory, Bethel Valley Rd, PO Box 2008, Oak Ridge, TN 37831, (4) Biochemistry & Molecular Biology, University of Georgia, B222A Davison Life Sciences Complex, Green St., Athens, GA 30602
Hydrogen production from less costly renewable abundant biomass can both decrease reliance on fossil fuels and achieve net greenhouse gas emissions, but current chemical and biological means suffer from low hydrogen yields or/and severe reaction conditions. We have invented a novel enzymatic reaction for producing hydrogen from starch and water as C6H10O5 (l) + 7 H2O (l) à 12 H2 (g) + 6 CO2 (g) [PLoS ONE, 2007, 2:e456]. The overall process is spontaneous and unidirectional mediated by 13 enzymes together. This new conversion can be catalyzed at 30oC and atmospheric pressure. Special features, such as, safe storage of solid carbohydrates, modest reaction conditions, easy separation of the products and reactants (gas/liquid), complete conversion, high hydrogen storage capacity (14.8 H2 mass%), no toxic by-products generated (e.g., CO or sulfuric oxide), and no special infrastructure required, make carbohydrate as a hydrogen carrier more appealing, as compared to other hydrogen carriers, such as methanol and ammonia. Life cycle analysis suggests that the carbohydrate-hydrogen-fuel cell system would be the most energy efficiency power train system; system analysis suggests that it would have the same energy storage density as that of liquid fuel-internal combustion engine (MJ/kg); economic analysis suggests that it would be one of the cheapest fuel systems based on the final mechanical output. With technology improvement, we envision that we will drive vehicles powered by carbohydrates someday.
