Karen Bleier/AFP/Getty Images
A new study shows that it's more efficient to use switchgrass to produce ethanol than corn. That makes it an attractive new alternative fuel.
Karen Bleier/AFP/Getty Images
In his January 2006 State of the Union address, President George Bush presented a laundry list of things his administration would do to help America kick its oil habit.
"We'll also fund additional research in cutting-edge methods of producing ethanol, not just from corn but from wood chips and stalks and switchgrass," the president promised.
Many Americans had never heard of switchgrass back then.
Now a lot of switchgrass has been through the mill, so to speak. There has been little evidence that growing grass could actually make a dent in the demand for oil. But now there's new research showing that this prairie plant might actually be a good source of ethanol.
That could be good news. Right now, Americans get their ethanol fuel from corn — so much of it that corn prices have been bouncing up near historic levels. A lot of economists say if the country wants more ethanol, it should not come from food.
Thus, switchgrass. It's a kind of prairie grass, but you don't have to go to a prairie to find it. For example, it grows on the banks of the Chesapeake Bay in Maryland, where Ken Staver has been tending a plot for years. It can reach 6 feet high, is yellowish and is as stiff as a pencil.
"You can see it's done very well here," says Staver, a scientist with the University of Maryland, "with very little care other than when we planted it 10 years ago when we used some herbicide during the establishment phase. But literally the only thing we do out here every year is harvest it."
Switchgrass contains cellulose, the starting material that, with enough heat and the right enzymes and chemicals, can be made into ethanol fuel.
Easy to Grow and Harvest
Staver says one of the good things about this grass is that it pretty much grows by itself.
"It's considered a perennial plant," he says, "so it does reseed some, but mostly these are the original plants. It's not growing back from seedlings every year, it's growing back from the same rootstock."
So you don't have to plant it every year or even fertilize it much. And it's easy to harvest.
These things are essential to make fuel from plants — so-called biofuels. The more energy used to make them — for example, gas for tractors, or electricity to convert them into a liquid fuel — the lower your "net energy yield." In short, if it takes close to a gallon of gasoline to make a gallon of biofuel, why bother?
In a new study, plant scientist Ken Vogel found switchgrass is worth the bother. He's with the federal government's Agricultural Research Service in Nebraska.
Vogel spent five years with farmers growing switchgrass in the Midwest. It was one of the biggest experiments with actual crops. He calculated with what might seem like mind-numbing thoroughness everything that went into each plot.
"This includes the energy used for fuel," he says, "the energy used to make the tractors, the energy used to make the seed to plant the field, the energy used to produce the herbicide, the energy used to produce the fertilizer, the energy used in the harvesting process."
More Efficient than Corn
For every unit of energy used to grow the switchgrass, Vogel says he could get almost 5 1/2 units worth of ethanol. That's a lot more efficient than making ethanol from corn, he says. He's bullish on switchgrass' future.
"The bottom line is perennial energy crops are very net energy-efficient. It is going to be economically feasible, the basic conversion technology has been developed, and it is going to be a viable process."
Vogel has focused on the growing part of the process. He hasn't demonstrated that commercial distilleries can actually achieve the same level of efficiency.
One issue is how to power the distillery. If you use electricity made from coal, you lose some of the advantage of biofuels. Vogel argues that a distillery could regain that advantage by burning leftover parts of the switchgrass to generate energy.
Vogel's research appears in the latest issue of the journal, Proceedings of the National Academy of Sciences.