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Interviewees: Jim Dumesic, Univ. Wisconsin-Madison College of Engineering
The Real Thing
The prospect of growing our own gasoline, diesel and even jet fuel is getting some real lift from engineers at the University of Wisconsin-Madison. They’ve shown they can make all of these transportation fuels from the same inedible plant sugars proposed for making ethanol.
“The fuel we make is identical to that of gasoline, jet and diesel fuel, there’s no difference chemically,” says Professor Jim Dumesic of the university’s College of Engineering. “The difference, however, is that we make these molecules not from petroleum, which is nonrenewable, but we make them from renewable biomass, so that when the biomass grows, it uses up CO2.”
Dumesic and his team say the discovery will help create plant-based fuels that don’t take away from our food supply.
“For example, agricultural residues, like corn stover. Could be energy crops like switchgrass. It could be waste material. These are all things that contain cellulose and cellulose is something now that really we cannot eat,” he says.
“The current idea is to take those sugars and, by fermentation, make ethanol,” Dumesic explains. “We would take those same sugars now, and instead of going the ethanol route, we would propose to pass them over these catalysts and convert them directly into liquid hydrocarbons for gasoline, jet, and diesel fuel.”
They wrote in the journal Science that they use a recyclable catalyst to turn sugar water into a layer of oily chemicals that separate from the water. Then they use another catalyst to upgrade the oil into the same fuels we now make from petroleum, which contain much more energy than ethanol.
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“Ethanol itself– although it burns very well, it has very high octane — it has a very low energy content so the energy per liter or per gallon of your fuel is about 30 or 40 percent lower with ethanol than it is with gasoline.”
The process doesn’t convert all of the sugars into transportation fuels, but Dumesic says all of the end products are valuable replacements for petroleum products.
“We’re making about 40 percent of the theoretical maximum [of gasoline] now. Clearly, with more research, we would like to understand how to get more of that carbon into the gasoline pool,” he says. “But on the positive side, even at the current time, the carbon that’s not going into gasoline is going into things like propane, butane, and those are valuable hydrocarbons for energy in the home sectors.”
The researchers say several years of basic research, notably funded by the National Science Foundation, are bearing fruit.
Indeed, University of Massachusetts-Amherst researcher George Huber, a former student of Dumesic’s, recently published a process for making gasoline from wood cellulose.
According to Huber, “It will still likely be several years before these processes become commercially available. However, funding basic sciences allows us to quickly develop these new processes and develop alternative sources of domestically produced liquid transportation fuels.”
Huber also uses catalysts, and produces the aromatic carbon compounds found in gasoline. Dumesic’s process operates at lower temperatures, and makes an oil that can be converted to aromatics as well as the hydrocarbons found in diesel and jet fuels, Dumesic says. And he says that a company he helped found in 2002 is also pursuing a similar process and working with major oil companies to develop it.
More research is also needed, and happening, into understanding carbon balances and managing our land, agricultural, and forest resources for the future biofuels economy.
Dumesic says ethanol will still likely be a part of the mix. “I don’t think it will be either-or,” he says. “Many people are really talking about biorefineries and these would be sites at which you bring in biomass in a distributed fashion and make all sorts of fuels and chemicals for different applications. So I would like to believe that the processes we’re talking about are just one part of what you would imagine at an integrated biorefinery, and making ethanol might be part of that refinery as well.”
He says the land for growing such fuel crops is a limiting factor, but they estimate we could replace 50 percent our current petroleum use with these renewable fuels. That means conservation, efficiency and other energy alternatives are still very important for using these valuable resources.
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