Sustainable development is a pattern of resource use that aims to meet human needs while preserving the environment.  To solve numerous sustainability challenges, such as food production, CO₂ utilization, electricity storage, transportation fuel production, fresh water conservation, wildlife habitat restoration, or maintaining a small closed ecosystem for space travel and the survival of humankind,  I propose the carbon-neutral carbohydrate cycle, better than the methanol cycle proposed by the Nobel Winner George Olah.  In this cycle, carbohydrate is a source for food, feed, liquid biofuels, and renewable materials, a high-energy density hydrogen carrier (14.8 H₂ mass%) or a high-electricity storage carrier (~10 MJ electricity output/kg sugar).  Carbohydrate can be produced from natural photosynthesis by plants and will be produced by artificial photosynthesis in bioreactors.  Also, we need low-cost and high-efficiency conversions among carbohydrate, electricity, and hydrogen for better energy conversion and utilization.

         In this talk, I will present our efforts and visions for the carbon-neutral carbohydrate cycle. (1) By utilization of the most abundant renewable non-food lignocellulose, we have developed cost-effective isolation of sugars from non-food biomass, involving lignocellulose fractionation under modest reaction conditions ¹, cellulase engineering, and cellulose hydrolysis modeling. (2) For conversion of sugars to hydrogen or electricity, we have demonstrated the highest yield hydrogen production from sugars through cell-free synthetic pathway biotransformation (SyPaB). These chemical reactions can generate chemical energy (hydrogen) output 22% more than input by absorbing useless ambient-temperature thermal energy.  Also, our analysis suggests that ~5% of available biomass resource in the USA would be sufficient to meet the national needs of transportation fuels if we increase the energy utilization efficiency through sugar-hydrogen-fuel cell systems. (3) In order to increase carbohydrate supplies and applications, we have designed an artificial photosynthesis pathway that can fix CO₂ by electricity or hydrogen for production of carbohydrates or biofuels. These artificial photosynthesis processes are designed according to the design principles of synthetic biology, knowledge in the literature, and thermodynamics analysis. 

Dr. Yi-Heng Percival Zhang is associate professor in the Department of Biological Systems Engineering of Virginia Polytechnic Institute and State University (Virginia Tech, USA). He is an affiliated investigator of the DOE BioEnergy Science Center (BSEC).  Now he is also a cofounder and Chief Scientific Officer of Gate Fuels Co. (USA). 

Prior to joining Virginia Tech, he was a research scientist, postdoc associate, Ph.D. student at Dartmouth College, working with a biofuel pioneer – Prof. Lee R. Lynd, for validating feasibility of consolidated bioprocessing (CBP). (Consequently, Mascoma Co. was founded in 2005.)  He received his bachelor and master degrees in Biochemical Engineering Department of East China University of Science and Technology, Shanghai, China.  His master thesis advisors are Profs. Jian-Jiang Zhong and Jun-Tang Yu.

His research topics include (1) cost-effective release of fermentable sugars from non-food biomass through lignocellulose fractionation and cellulase engineering, (2) most efficient conversion of sugars to 2^nd liquid biofuels (e.g., hydrocarbons) and 3^rd generation biofuels (e.g., hydrogen and electricity) through cell-free synthetic pathway biotransformation (SyPaB), (3) CO₂ utilization through artificial photosynthesis for the production of carbohydrate as a source of food, feed, biofuels, an electricity storage compound, and a high density hydrogen carrier, and (4) energy efficiency analysis for energy conversion and generation.  Furthermore, he advocates sugar-hydrogen-fuel cell vehicles (Crazy Idea of Year 2006 of Esquire magazine) and the carbon-neutral carbohydrate economy. 

He is a pioneer in cell-free synthetic biology. His breakthrough of the highest yield hydrogen production from biomass sugars has been highlighted by the Royal Society of the UK as “the beginning stage of a cheap, green and high-yield hydrogen production”.  These chemical reactions can generate chemical energy (hydrogen) output 22% more than input by absorbing useless ambient-temperature thermal energy.  Also, he has invented the lowest cost biohydrogenation technology for synthesis of chiral compounds and designed the highest energy efficiency and most water-saving (artificial) photosynthesis for producing sugars from CO₂. 

He has published more than 50 peer-reviewed journal papers, several invited feature articles, 10 book chapters, and filed 15 patents disclosures. Four of his patent disclosures have been licensed to two biofuels/biotechnology companies – Mascoma (USA) and Biomethodes (French) and five are on an option-to-license stage; five are under option-to-license by two other companies.  He has received several distinctions, such as Biotechnology and Bioengineering Daniel IC Wang Award (2010), Sunkist Young Designer Award (2009), BP young scientist Award (2008), Dupont Young Faculty Award (2008), Air Force Young Investigator Award (2007), ACS PRF New Faculty Award (2006), Ralph E. Powe Junior Faculty Enhancement Award (2005), to name a few.