Since 2007, researchers at the U.S. Department of Energy's BioEnergy Science Center (BESC) at Oak Ridge National Laboratory have been looking for ways to make cost-effective biofuels from nonfood "cellulosic" plant fibers.
Recently, one of the teams discovered that the same phenomenon that allows hardwood trees to bend without breaking might also make them more suitable as a bioenergy feedstock.
Cellulosic biofuels are produced by fermenting plant sugars, or cellulose, into alcohol. In a recent study published in Energy & Environmental Science, the BESC team described the properties of "tension wood" – the cells of hardwood trees formed in response to bending stress.
The team found that tension wood contains higher numbers of woody cells, thicker cell walls, more crystalline forms of cellulose and lower lignin levels than normal wood. All of these characteristics make it desirable as a biofuel feedstock.
According to Oak Ridge National Laboratory's Udaya Kalluri, a co-author on the study, wood normally contains 40 to 55 percent cellulose. However, tension wood in poplar trees has a "special type of cell" that is composed of more than 90 percent cellulose.
Although tension wood itself is not considered to be a viable feedstock option, studying its unique characteristics could help scientists select and design bioenergy crops tailored for increased sugar production.
"If you increase the cellulose in your feedstock material, then you can potentially extract more sugars as the quality of the wood has changed," Kalluri said in a statement. "Our study confirms this phenomenon."