UW News

September 4, 2015

Poplar trees are best bet for biofuel in UW-led research project

UW News

Groves of poplar trees could one day fuel our vehicles and be the source of chemicals that we use in our daily lives.

Poplar materials, including bark, leaves and wood, are used to make cellulosic ethanol.

Poplar materials, including bark, leaves and wood, are used to make cellulosic ethanol.Dennis Wise/University of Washington

A five-year, $40 million study is laying the foundation for a Pacific Northwest industry that converts sustainably produced poplar feedstock into fuels and chemicals.

The research, led by the University of Washington, will seed the world’s first wood-based cellulosic ethanol production facility. The handful of other cellulosic ethanol factories use agricultural waste to convert feedstock into sustainable transportation fuels.

The U.S. Department of Agriculture-funded project is in its final year, and the consortium of 10 academic institutions and private companies will gather at the UW Sept. 8-10 to share results and finalize research projects. They identified hybrid poplars as a beneficial feedstock because of the tree’s fast growth, year-round availability and wood that is readily broken down to fermentable sugars.

ZeaChem, a Colorado-based biofuels company and one of the industry partners in this study, is moving ahead with plans to build a commercial production facility in Boardman, Oregon, in 2016 that will produce fuel-grade ethanol and bio chemicals.

“We’ve established that poplar is a viable and sustainable feedstock for the production of fuels and bio-based chemicals,” said Rick Gustafson, a UW professor of bioresource science and engineering, who leads the project. “We’ve provided fundamental information that our industry partners can use to convince investors that production of fuels and chemicals from poplar feedstock is a great investment.”

The research team, called Advanced Hardwood Biofuels Northwest, set up five demonstration tree farms with different varieties of poplar. None of the trees is genetically engineered, but instead researchers bred them to thrive in different environments and to grow fast. The trees can gain up to 20 feet a year, allowing for a harvest every two or three years.

“They grow like mad,” Gustafson said. “The production growth rate of these trees has just been phenomenal.”

When a poplar tree is cut, its stump naturally sprouts new shoots and the next generation of trees grow out of the parent stumps. Each tree can go through about six cycles of this regrowth before new poplars must be planted, Gustafson said.

Shannon Ewanick with the UW's Biofuels and Bioproducts Laboratory operates a pretreatment reactor, known as a "steam gun."

Shannon Ewanick with the UW’s Biofuels and Bioproducts Laboratory operates the pretreatment reactor, known as a “steam gun.”Dennis Wise/University of Washington

A number of UW faculty members and students, mainly in the UW’s School of Environmental and Forest Sciences, have contributed to different aspects of this broad research project. They explored the pros and cons of processing whole trees verses using clean wood chips, developed catalysts to convert ethanol to jet fuel, examined the efficacy of endophytes — microorganisms — that live within the trees that provide benefits such as nitrogen fixation, assessed the social impact on potential landowners, and looked at available land for poplar tree farms and the impact climate change may have on growing them.

The UW team also has refined the process of converting the poplar trees to fuel.

In this process, sugars are extracted from the poplar tree using a combination of thermal/chemical pretreatment and enzymatic reactions. The pretreatment step is performed in a high-pressure reactor to efficiently extract some of the sugars and to open the wood structure to enable enzymes to access carbohydrates remaining in the wood.

Shannon Ewanick collects products exiting the pretreatment reactor after the reactions have fractioned the biomass.

Shannon Ewanick collects products exiting the pretreatment reactor after the reactions have fractioned the biomass.University of Washington

These sugars can then be fermented to different products including ethanol and acetic acid. Poplar is ideal for this process because they grow quickly and have relatively accessible carbohydrates in the wood.

Process improvements developed on the laboratory scale at the UW can be tested at a demonstration scale at ZeaChem’s demonstration biorefinery in Boardman and then applied at a commercial scale once that facility is constructed.

“Advanced Hardwood Biofuels is more than a big research program,” Gustafson said. “We are setting the stage for a new, sustainable enterprise for the Pacific Northwest.”

Project collaborators and reporters interested in this project can take a tour of the UW biorefinery pilot plant and laboratory facilities on campus Sept. 8 as part of the team’s annual meeting.

The other institutions involved are Washington State University, University of California, Davis, University of Idaho, Oregon State University, the Agriculture Center of Excellence, Greenwood Resources, Inc. and the Rocky Mountain Wildlife Institute.


For more information, contact Gustafson at 206-543-2790 or pulp@uw.edu.