Runge estimated that in the United States alone, some 1.3 billion tons of cellulose material could be harvested for biofuel use. Cellulose is basically fiber, and can be found in things ranging from switchgrass to trees such as hybrid poplar and willow. Even materials from other industries, like corn stalks after harvest, could be used for cellulose fuel. While there is some debate over devoting land to growing crops specifically for fuel, the sheer volume of cellulosic material still makes it a tremendous source for biofuel.
With so much material to work with, why isn’t cellulose biofuel flooding the market? To use cellulose as a fuel, it must be broken down into sugar. This may not seem like much of a problem, but Runge explained cellulose is engineered specifically to prevent this process.
“If you think about it, nature -- the trees and the grass -- they were built to withstand microbial attacks that want to take it down to sugar so they can eat it,” Runge said. “Nature’s got all kinds of defense mechanisms to make sure that doesn’t happen.”
There are currently no commercial producers of cellulosic fuel, but Mark Knaebe and his fellow technologists at the U.S. Forest Products Laboratory in Madison, WI, are attempting to develop the technology. Because cellulose is so abundant, can be continuously regrown and harvested, and is one of the cleanest burning materials, Runge rated it the number one fuel, despite this slight lag in technology.