The remains of plants processed for human purposes molder in landfills across the world. Whether waste paper or raked leaves, the plant remnants still contain cellulose, a sugar in greenery that bonds with the chemical compound lignin to furnish a plant's structure. Microbes living in the landfills break down this cellulose into methane, which slowly seeps to the surface and into the atmosphere, where it is a potent greenhouse gas. BlueFire Ethanol, Inc., in Irvine, Calif., would rather harvest that energy for use as cellulosic ethanol fuel.
"We produce 70 gallons of ethanol per ton of waste," says engineer Arnold Klann, BlueFire's president and CEO. "The trick is unlocking the sugar molecule from the lignin, which is the glue that holds it together."
BlueFire estimates 40 billion gallons of cellulosic ethanol could be produced from plant waste destined for the landfill, providing as much as one third of all U.S. transportation fuel needs. And, if other forms of waste, such as the stalks of corn plants (corn stover) or the remnants of timber harvest are included, Klann says, "we have enough feedstock in the U.S. to offset 70 percent of the oil import."
BlueFire is set to open its first plant at a landfill in Lancaster, Calif., later this year and hopes to use U.S. Department of Energy (DOE) funding to open a second by the end of 2008, Klann says. Together the two plants would produce, at best, 22 million gallons of ethanol a year by using sulfuric acid to break the lignocellulose bonds and then burning the leftover lignin to power fermentation of the cellulose into ethanol. "The lignin we recover makes up 70 percent of the steam and electricity we need," Klann notes. "The other advantage of siting at a landfill is that they have methane gas. We can burn that in our boiler and generate huge carbon credits."
Given the potential benefits, Congress has provided $10 million in funding—and the DOE has asked for $30 million more—to develop a second facility employing the process, as well as millions more for similar cellulosic biorefineries, such as the Range Fuels plant in Soperton, Ga., that converts wood waste into fuel.
Biofuels from waste avoid the carbon and energy debts incurred by more common examples such as ethanol from corn or diesel from soy. "The thing we know will work is if you use waste products," says agricultural expert Tim Searchinger of Princeton University, who led recent research showing that most biofuels do little to slow and may even increase global warming. "If everything is done right, probably we can use corn stover without other problems, though it might mean you have to grow a cover crop."
Biofuels also offer one of the few methods currently available for storing solar energy, notes chemical engineer Charles Wyman of the University of California, Riverside. "Biomass to liquid fuel, electricity for charging of a battery or generating hydrogen, [those are] really our options," he says. "The best way to store solar energy is called biomass."
BlueFire has already operated such a plant to convert wood waste into ethanol in Japan to demonstrate the feasibility of the technology. As a result, the government of that country has decided to mandate blending 1 percent of ethanol into gasoline for the first time. And Klann believes this technology could prove most useful in the developing world, where plant waste is typically burned rather than buried. "What we have to do as a society is figure out how to move ourselves around in a way that is low-cost and has minimal effect on the environment," he says. "Ethanol is not a bad fuel."