Novel sugar-to-hydrogen technology promises transportation fuel independence

The idea began as a theory. The research was based on Zhang's previous work pertaining to cellulosic ethanol production and the ORNL and University of Georgia researchers' work with enzymatic hydrogen production. UGA Distinguished Professor Adams is co-author of the first enzymatic hydrogen paper in Nature Biotechnology in 1996. The researchers were certain they could put the processes together in one pot. They tested the theory using Oak Ridge's hydrogen detectors and documented that hydrogen is produced as they predicted.

Mielenz, who heads the Bioconversion Group in ORNL's Biosciences Division, attributed the successful research to a unique collaborative working relationship between scientists, lab divisions, and universities.

"Pairing our biomass conversion capabilities with facilities for studying renewable hydrogen production in the lab's Chemical Sciences Division was a key to this project,"Mielenz said. "This also shows the value of partnerships with universities such as Virginia Tech and the University of Georgia."

It is a new process that aims to release hydrogen from water and carbohydrate by using multiple enzymes as a catalyst, Zhang said. "In nature, most hydrogen is produced from anaerobic fermentation. But hydrogen, along with acetic acid, is a co-product and the hydrogen yield is pretty low -- only four molecules per molecule of glucose. In our process, hydrogen is the main product and hydrogen yields are three-times higher, and the likely production costs are low – about $1 per pound of hydrogen. "

Over the years, many substances have been proposed as "hydrogen carriers,"such as methanol, ethanol, hydrocarbons, or ammonia – all of which require special storage and distribution. Also, the thermochemical reforming systems require high temperatures and are complicated and bulky. Starch, on the other hand, can be distributed by grocery stores, Zhang points out.

"So it is environmentally friendly, energy efficient, requires no special infrastructure, and is extremely safe. We have killed three birds with one stone,"he said. "We have hydrogen production with a mild reaction and low cost. We have hydrogen storage and transport in the form of starch or syrups. And no special infrastructure is needed."

"The next R&D step will be to increase reaction rates and reduce enzyme costs," Zhang said. "We envision that in the future we will drive vehicles powered by carbohydrate, or energy stored in solid carbohydrate form, with hydrogen production from carbohydrate and water, and electricity production via hydrogen-fuel cells.

"What is more important, the energy conversion efficiency from the sugar-hydrogen-fuel cell system is extremely high – greater than three times higher than a sugar-ethanol-internal combustion engine,"Zhang said. "It means that if about 30 percent of transportation fuel can be replaced by ethanol from biomass as the DOE proposed, the same amount of biomass will be sufficient to provide 100 percent of vehicle transportation fuel through this technology."

In addition, the use of carbohydrates from biomass as transportation fuels will produce zero net carbon dioxide emissions and bring benefits to national energy security and the economy, Zhang said.