Purdue researcher studies poplar genetics, ethanol conversion

By Matt Soberg | October 25, 2011

In separate studies, Purdue University is genetically altering poplar for cellulosic ethanol production while creating a model to project poplar production potential for the industry. Rick Meilan, associate professor of molecular tree physiology, leads the research and received funding from Hoosier Energy, an Indiana-based electrical cooperative, and the U.S. DOE. 

Despite the lack of commercial production in the U.S., according to Meilan, findings from both studies could be used to further develop the cellulosic ethanol industry. “There are two important criteria when evaluating a potential bionergy crop. One is how much biomass it produces. The other, which is equally important, is how efficiently the sugars contained in the biomass can be converted into fuel. As the technology develops it will become even more profitable for growers,” he said. 

Three years ago through DOE support, Meilan, who specializes in genetic modification, began developing poplar that can be more efficiently converted to cellulosic ethanol. Meilan and his research team started test plots looking for trees with less stringent lignin composition, making it easier to extract convertible sugars.  

In a perfect world, feedstock suppliers would be able to ‘double dip’ by providing both corn and stover to produce ethanol, however, the lignin gets in the way, according to Meilan. “With the release of its full genome sequence in 2006, poplar contains genetics that makes it a model system for modification,” he said. 

More recently, Meilan began a five-year study, funded by Hoosier Energy, to determine the conversion efficiency of poplar as a biomass feedstock. The study includes 69 varieties planted under different soil, climate, fertilizer and irrigation combinations. The researchers want to know which trees perform best,  expected yield and what type of financial return can be projected. 

The study includes trial plots at the Pinney-Purdue Agricultural Center east of Valparaiso and the Southwest-Purdue Agricultural Center north of Vincennes.  The centers are university-managed farms where crops can be grown, documented and harvested for research purposes.

At each center, the researchers planted 2000 poplar sticks, measuring 8 inches long, which were donated from ArborAmerica Inc. and GreenWood Resources Inc.  Poplar can be vegetatively propagated, meaning “we can take a stem segment and just shove it into the ground and it will spontaneously produce roots in the portion of the stick that’s beneath the ground,” said Meilan.  Planted in May, some trees grew to over 15 feet by October, and some can reach 90 feet in six years.