BOARDMAN — The poplar trees here grow 10 feet a year, transforming an irrigated stretch of desert near the Columbia River into a neatly pruned forest.

For now, the trees provide lumber for cabinets and pulp for paper.

But in the years ahead, energy entrepreneurs hope the pulp from poplar can be turned into ethanol, helping resuscitate the Northwest’s floundering biofuels industry.

One of the first investments in this region will be near Boardman, where construction is scheduled to begin later this year on a demonstration plant that will produce about 1.2 million gallons a year of ethanol from poplar.

“We’ve raised $34 million, and that’s enough to move us forward,” said Jim Imbler, the chief executive officer of ZeaChem, the Colorado-based company that is building the plant.

The push to develop poplar ethanol comes at a dismal time for the Pacific Northwest biofuels industry. Just a few years back, the industry attracted hundreds of millions of dollars from investors and legislative support from politicians eager to see the region’s farm and forest economies bolstered by a new push into energy production. But the first three large-scale biofuel plants launched in the region ended up importing energy crops from outside.

Today, they all are floundering, knocked down by last year’s run-up in crop prices and an implosion in oil prices as the recession took hold.

Imperium’s biodiesel plant in Aberdeen, Wash., built to use Canadian canola, is idle. A Clatskanie plant that tried to make money converting Midwestern corn into ethanol opened in the summer of 2008, then shut down in January.

A second corn-ethanol plant near Boardman still operates. But the plant is in Chapter 11 bankruptcy reorganization as its parent company, Pacific Ethanol, struggles to pay off debts.

The biofuels industry is also under assault from critics who question both the ethics and environmental wisdom of diverting food crops such as corn into fuel. They question whether the thirst for material to produce biofuels is spurring a global expansion of agriculture, with wide-ranging repercussions on water, forests cleared for crops and soil fertility.

“There is a finite amount of land on this Earth … adding additional land use demands for agriculture has consequences, and that is undeniable,” said Kate McMahon, who represents Friends of the Earth.

Despite the controversy, the U.S. ethanol industry — bolstered by federal and state subsidies — has mustered impressive growth.

Largely corn-based ethanol production hit 9 billion gallons in 2008, nearly double the output from just two years earlier. Much of the ethanol is produced in the Midwest grain-belt states.

That fuel represented — by volume — about 6 to 7 percent of total gasoline consumption.

Many entrepreneurs are banking that the federal government’s involvement will drive a dramatic expansion of the biofuels industry — and help make poplar ethanol commercially feasible.

A federal mandate requires the production of 36 billion gallons of ethanol and other biofuels by 2022. The law calls for some 15 billion gallons of that fuel to come from wood, wheat straw, corncobs or other cellulosic materials rather than foods such as corn or sugar cane. That’s spurring research and development efforts.

But breaking down cellulosic material and turning it into fuel is a more complicated and costly undertaking than converting starch or sugar crops to ethanol.

To date, there are still no commercial-scale cellulose-to-ethanol plants operating in North America. Most of the plants are in a pilot or demonstration stage, and, like the ZeaChem project near Boardman, still under development.

One oil-industry skeptic likened the quest to produce ethanol from cellulose to the search for the Holy Grail.

“But remember, they never found the Holy Grail,” said John Felmy, an economist for the American Petroleum Institute at a 2007 conference of the Renewable Fuels Association.

ZeaChem, formed in 2002, is using a technology that harnesses the same bacteria used by termites as they feast on wood. Imbler, ZeaChem’s chief executive officer, believes the technology could eventually be competitive with oil selling at $40 to $50 per barrel. (Oil prices on the New York Mercantile Exchange were at $71 on Tuesday.)