(791e) Carbohydrate Could Be the Best Electricity Storage Compound and a High-Density Hydrogen Carrier

Electricity is a high-quality secondary energy, which can be generated from renewable primary energies and fossil fuels. Carbon-neutral electricity generation is becoming more and more important, but most of them, such as wind and solar electricity, suffer from large output variations. Therefore, it is vital to store electricity in the form of chemical compounds. Among numerous potential chemical compounds, such as hydrogen, isobutanol, methanol and hydrocarbons, we suggest that carbohydrates (e.g., starch, cellulose, glucose) could be the best electricity storage compound with a combustion energy density of 17 MJ/kg and an electricity output density of >3,000 Wh/kg [1].  We designed a novel biological CO2 fixation pathway that can fix CO2 by using hydrogen or electricity for producing carbohydrate mediated by cell-free cascade enzymes [1]. In this talk, we will present our efforts in developing building blocks and building modules for this ambitious project and conduct proof-of-concept experiments. Through the above bioconversion plus our previous achievements such as theoretical conversion of carbohydrate to hydrogen or electricity [2] and low-cost enzymatic conversion of cellulose to starch (unpublished), the electricity-carbohydrate-hydrogen cycle would not only supplement current and future primary energy utilization systems for facilitating electricity and hydrogen storage and enhancing secondary energy conversion efficiencies, but also address such sustainability challenges as transportation fuel production, CO₂ utilization, fresh water conservation, food and feed production, and maintenance of a small closed ecosystem in emergency situations [1].  In a word, carbohydrate would become a new oil in the future.

1. Zhang Y-HP, Huang W-D: Constructing the electricity-carbohydrate-hydrogen cycle for a sustainability revolution. Trends Biotechnol. 2012, Epub.             DOI: 10.1016/j.tibtech.2012.02.006.

2. Zhang Y-HP, Evans BR, Mielenz JR, Hopkins RC, Adams MWW: High-yield hydrogen production from starch and water by a synthetic enzymatic pathway. PLoS One 2007, 2:e456.