Fast-Growing Trees Could Take Root as Future Energy Source

A bold plan to replace 80% of the nation's transportation fuel with ethanol derived from poplar trees.

A hybrid tree that can reach 90 feet in six years and be grown as a row crop on fallow farmland could represent a major replacement for fossil fuels.

Purdue University researchers are using genetic tools in an effort to design trees that readily and inexpensively can yield the substances needed to produce alternative transportation fuel. The scientists are focused on a compound in cell walls called lignin that contributes to plants' structural strength, but which hinders extraction of cellulose. Cellulose is the sugar-containing component needed to make the alternative fuel ethanol.

"Poplar is a low-maintenance crop; plant it and wait seven years to harvest it," Meilan said. "You're not applying pesticides every year; you're not trampling all over the site every year and compacting the soil. You're allowing nutrients to recycle every year when the leaves fall and degrade. In addition, you are more likely to have greater wildlife diversity in poplar plantings than in agricultural fields."

Experts are proposing planting the trees in rows just like any field crop. The basis of these tree plantations will be tens of millions of acres that the DOE and USDA have inventoried as being unused or fallow - previously used farmland that is standing empty because farmers are paid not to grow anything.

Researchers believe that using the hybrid poplar in its present form could produce about 70 gallons of fuel per ton of wood. Approximately 10 tons of poplar could be grown per acre annually, representing 700 gallons of ethanol. Corn currently produces about 4.5 tons per acre per year with a yield of about 400 gallons of ethanol. Changing the lignin composition could increase the annual yield to 1,000 gallons of ethanol per acre, according to experts. Planted on 110 million acres of unused farmland, this could replace 80 percent of the transportation fossil fuel consumed in the United States each year.

Previously I looked at a plan to grow switchgrass which had similar sort of numbers, 1,312 gallons of ethanol per acre on 114 million acres to create 108 billion gallons. Not sure the relative merits of switchgrass vs. poplar but either way we are looking at lots more biofuels in the future.

via Newswise