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High energy liquid fuel created from sugar

U.S. scientists have transformed sugar into a liquid transportation fuel they say has a 40 percent greater energy density than ethanol.

University of Wisconsin-Madison Professor James Dumesic and colleagues describe a two-stage process for turning biomass-derived sugar into 2,5-dimethylfuran, or DMF.

"Currently, ethanol is the only renewable liquid fuel produced on a large scale," said Dumesic. "But ethanol ... has relatively low energy density, evaporates readily, and can become contaminated by absorption of water from the atmosphere. It also requires an energy-intensive distillation process to separate the fuel from water."

Not only does dimethylfuran have higher energy content, Dumesic said it also is not soluble in water and therefore cannot become contaminated by absorbing water from the atmosphere.


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DMF is stable in storage and, in the evaporation stage of its production, consumes one-third of the energy required to evaporate a solution of ethanol produced by fermentation for biofuel applications, he added.

The biofuel has a higher energy content than ethanol, the only renewable liquid fuel currently produced on a large scale. It also doesn't absorb water from the atmosphere, a shortcoming of ethanol, said James Dumesic, one of the researchers and a professor of chemical and biological engineering at the university.

Concern over diminishing oil reserves and the threat of global warming caused by burning fossil fuels have scientists searching for alternative energy sources. By chemically engineering sugar through a series of steps involving acid and copper catalysts, with salt and butanol as a solvent, the researchers have created a path toward what could be a better fuel.

Gasoline-like alternative:

"Optimistically we might be just a couple of years away. It's a two-step process to convert the fructose into DMH, but the two steps are very similar to the processes already used in the petroleum industry," Dumesic said in an interview.

The process of making the biofuel is a balancing act of chemistry, pressure, temperature and reactor design. Fructose is initially converted to a substance called hydroxymethylfurfural, or HMF, which is then converted to DMF.

The biofuel has 40 percent greater energy density than ethanol, the renewable fuel made from corn, Dumesic said.

"Ethanol suffers from several limitations," he said. "It has relatively low energy density, evaporates readily and can become contaminated by absorption of water from the atmosphere. It also requires an energy-intensive distillation process to separate the fuel from water," he said.

DMF is not soluble in water and therefore cannot be contaminated by absorbing water from the atmosphere. It also takes less energy than ethanol to produce.

Practical application:

Researchers are gearing up to produce DMF in larger quantities for testing in gasoline engines.

"The main concern I would have about getting too exuberant is, we really don't know the environmental toxicological factors associated with the widespread use of DMF," Dumesic said. "We think it's very important to have experts other than ourselves really make sure that widespread use of this fuel would, in fact, be safe for the environment and for people."

The research shows that a biofuel can have the same energy density as petroleum, which is important in finding alternatives to fossil fuels.

But DMF won't necessarily replace ethanol, at least not in the near future.

Wisconsin has seven ethanol plants in operation, with eight more under construction or in planning stages. Currently, Wisconsin is the nation's seventh-largest ethanol producer, with about 20 percent of the state's corn crop destined for the fuel additive this year.

"The big advantage of ethanol is it's a well-established technology," Dumesic said. "It's something we know how to do safely, and that's hard to compete with. But in terms of energy density, ethanol is low."

Ethanol and DMF could both be made from simple sugars found in renewable energy sources such as paper-mill waste.

Apples and oranges could be another fuel source.

"But I think fruit would be a very small supply," Dumesic said.

A viable competitor?
The UW-Madison approach "heralds the advent of a second generation of biofuels," wrote Lanny Schmidt and Paul Dauenhauer, professors of chemical engineering and material sciences at the University of Minnesota, in a peer review of the research.

This is a "ground-breaking example of interdisciplinary engineering that may well dictate the future of biomass conversion," the researchers noted.

But investors in ethanol plants aren't necessarily worried that DMF will become a competing fuel.

The research is a "moot point" until there's a cost-effective way to convert bio-mass into sugar, said James Hanke, director of Badger AgVest, a group that encourages biofuel investments.

Dumesic co-founded Virent Energy Systems, a renewable-energy startup firm that's looking to deploy a different chemical process involving sugar that Dumesic and a former colleague developed in the same UW lab.

"We work closely with his labs, and any technology that comes out of there we tend to look at and decide whether we can be the commercialization partner," said Eric Apfelbach, Virent president and chief executive.

Virent is studying the new process, and how to make the fuel in high enough quantities, Apfelbach said.

"We've got to do it at a price that's reasonable," Apfelbach added.

Virent has seven small pilot projects making gasoline from sugar. That research is backed in part by the $7.5 million in funding it won last year from the venture capital arms of Cargill and Honda.

Release link: http://www.themoneytimes.com/news/20070622/high_energy_liquid_fuel_created_from_sugar-id-105186.html