First it was corn. Then came sugar cane, cooking oil, switch grass, and you name it researchers have tried it in the name of saving the planet from carbon emissions.
But, just when we all thought scientists had exhausted the possibilities, an interdisciplinary team of researchers from the University of Maryland College Park and Bowie State University have begun working on ways to turn poplar trees into high-yield crops for biofuels including ethanol, the renewable biofuel used in gasoline blends and flex-fuel vehicles.
Funded by a $3.2 million, four-year grant from the National Science Foundation's Plant Genome Research Project, which supports research on plants seen as having economic and agricultural importance, researchers Gary Coleman, Ganesh Sriram and Jianhua Zhu of College Park and George Ude of Bowie State are using the recently completed poplar genome to look for ways to improve the tree's nitrogen processing capability, which would enhance its growth rate and feasibility for use in fuel production.
Although corn has long been the crop of choice for biofuel production in the U.S., though it is renewable, home-grown (unlike foreign oil) and plentiful, it may not be the best solution.
"We need to develop an alternative crop that we use exclusively for biofuels and not food," says Sriram, assistant professor of chemical and biomolecular engineering at the University of Maryland's A. James Clark School of Engineering.
Enter poplar trees (also known as cottonwood or aspen), which is already commonly cultivated for the production of paper and timber.
"What we want are trees like poplar that grow fast and efficiently so they can become the raw material for cellulosic [fiber-based] biofuel," Sriram says. "The carbon found in poplar could be converted into fuels just like the sugars we extract from corn."
Coleman, lead researcher and an associate professor of plant science and landscape architecture in the university's College of Agriculture and Natural Resources says there are many advantages of a poplar crop over traditional biofuel sources.
"Growing trees doesn't eat into farmland, and trees don't require a lot of maintenance during their growth cycle," he explains. "A dedicated energy crop like poplar would contribute to the development of a sustainable and renewable energy system."
While the hybrid trees would be grown on plantations and harvested without affecting existing woodlands, simply growing acres of poplar trees to convert into biofuel isn't enough to solve current fuel problems. Researchers already know how to make ethanol from fibrous plants, but for poplar to be truly effective as a biofuel source, its growth cycle needs to speed up and become more efficient. One of the keys to doing so is to understand how it stores and cycles nitrogen, since nitrogen is an important factor in the growth and productivity of trees and crops.
The fertilizers that help produce big harvests are rich in nitrogen, but are expensive and must be reapplied each year. Poplar is a perennial plant, capable of pulling nitrogen from its leaves, storing it through the winter, and redistributing it in the spring. And while a crop like corn must be replanted each year, a poplar tree is capable of regrowing itself from its roots after being cut, and may go through several cycles of growth and harvest throughout its life before a new tree needs to replace it.
"Both the growth in the spring and regrowth from roots after the stems are harvested depend on the availability of stored nitrogen," Coleman says. "The data we collect will allow us to understand mechanisms of nitrogen cycling, determine how to increase the rates of the cellular reactions, and identify the genes that play a crucial role in the process. Eventually, we should be able to breed a variety of poplar with a more efficient nitrogen process, optimized for growth and rapid maturity."
Source: University of Maryland College Park
Writer: Walaika Haskins