by Sally Colby
No matter what the project or process on a farm, fuel is always at the top of the discussion list. Rick Gustafson of the University of Washington and AHB project leader believes that the project he’s been involved with for the past six years will prove to be a valuable source for farmers who need fuel and who want to grow fuel in the future.
The Advanced Hardwood Biofuels (AHB) Northwest is a USDA funded consortium of university and industrial partners. Gustafson says that the project has a strong development component that involves fundamental research, with the ultimate goal of translating the research results into commercial viable enterprises.
“Our focus has to been to lay the foundation for an industry in the Pacific Northwest making fuels and chemicals starting from purpose-grown poplar feedstock,” said Gustafson. “We want to figure out how to grow trees sustainably; develop efficient biorefineries to convert that into fuels and chemicals.”
AHB was initiated in 2011 with a USDA grant of $40 million with the purpose of exploring the development of an advanced biofuel industry using regionally produced hybrid poplars as the main feedstock. The project integrates industry and university partners to support research, education and extension.
Gustafson says that when the project started, one of the main motivating factors was to reduce the amount of imported oil. “In addition, there’s good evidence that biocrops can boost rural economies,” he said. “The thinking is that if we can start making fuels and chemicals from crops, it would help these rural environments.”
However, changes in crude oil prices over the past 10 years have impacted the project. “When we started the project back in 2011, oil was over $100 a barrel,” said Gustafson. “At that point, making fuels from feedstock looked economically viable. But since then, the price of oil has dropped to about $40 a barrel, which makes it very difficult to compete.”
Despite oil prices, the project continued and five project areas were defined: feedstock, conversion, sustainability, education and extension. Several of which overlap.
“We’ve established that poplar is an excellent feedstock,” said Gustafson. “Before we got into the project, it was well known that poplar is a good biomass to feed to the bioconversion processes. You can fractionate it, separate the sugars from the lignin, and it’s clean. There were some issues about growing and harvesting the whole trees, and we still think it’s an excellent feedstock, but cost is problematic.”
Several demonstration farms have been established in the Pacific Northwest to study poplar: Pilchuk, WA; Hayden, Idaho; Jefferson, OR; and Clarksburg, CA. “These are 50 to 100 acres,” said Gustafson. “There are different soils, different climates, different altitudes. We have a number of clones planted on each of the tree farms so we can really assess how well the trees grow.”
Poplars are planted in a system that allows coppicing with about 1,500 trees per acre. Planting is usually done in spring and involves pounding a dormant poplar stick into the ground so that about 75 percent of the stick is below the surface with buds pointing up. Leaves start to appear within several weeks of planting. The poplar’s growth habit is such that it sends three to five shoots off the stump that’s already established, leaving a large stump to drive new growth. The first harvest is usually in two or three years, depending on location and growth.
Trees are allowed to grow for three more years and are harvested again. Additional shoots emerge and grow, and the planting is harvested again. “You can get about five or six (harvest) cycles before the stump starts to run out of gas and you have to replant and start over again,” said Gustafson, adding that establishing poplar is less costly than many other silviculture methods because trees are planted only once about every 20 years.
All poplar clones that have been tested have proven to thrive, although some have grown faster than others. Gustafson says that some of the trees on the Jefferson, OR farm were 20 feet tall and almost five inches in diameter and growing so well that there was concern that by the end of the third year, when harvest was scheduled, the trees might be too large for the harvester. “There’s thought that we may have to do the coppice harvesting every two years so the trees don’t get too big,” he said.
In Hayden (western Idaho), three-year old trees yielded 20 tons/acre, or about seven tons/acre per year of growth. “We believe that this will go up with the next coppice cycle,” said Gustafson. “They’ll be more established; the root system will be bigger. As we go forward with the project, picking better clones, there’s no reason this couldn’t get to 10 tons/acre per year.” Research also showed that yields from coppiced trees are much higher than yields from single stem plantations.
The harvesting system was developed in conjunction with NEWBio (Northeast Woody/Warm-season Biomass Consortium), a group working with short-rotation woody biomass crops in the northeast. “It’s a modified corn harvester that cuts the trees down, grinds them up and spits the wood into a truck,” said Gustafson. “What we found in harvesting our tree farms is that it works very efficiently. You can go up and down the rows at about five mph.” Gustafson added that the biggest improvement in efficiency will be reducing the number of places the machine has to turn around during harvest.
One of the negative aspects of growing poplar is that it isn’t a low-cost enterprise. However, Jeff Nuss, president of GreenWood Resources, told researchers that there are people willing to invest in growing poplar. “The downside is that $100/ton if you’re going to make a fuel is pretty expensive for biomass,” said Gustafson. “These days, with cheap oil, it’d have to be $50 or lower to make a go of it. This is something that needs to be addressed — is there a way that the cost of producing biomass feedstock can be reduced? The money is out there, it’s just a matter of having a cost-effective system so we can make money growing trees.”
One of the positive impacts of woody biomass crops is that wildlife thrive in woody crop plantations and farmers are becoming enthusiastic about growing poplar as they learn more about it. A survey of 878 Washington landowners revealed that about half were interested in learning more and a third said they’d be likely to grow a bioenergy crop in the next five years. “When we first started, farmers were pretty unenthusiastic about this,” said Gustafson. “In large part because of a legacy of planted poplar trees for the pulp and paper industry in the 1980s that did not work out well at all. Over time, many farmers and landowners have warmed up to the idea of having (poplar) as an alternative crop on their farmland.”
In addition to use as a fuel source, whole tree chips show great potential for bioconversion. One potential use for the crop is ecosystem services such as wastewater treatment plants, biorefineries and other water remediation systems.
“We’ve laid the foundation for renewable fuels and the chemicals industry in the Pacific Northwest,” said Gustafson. “We’ve done a lot of science on the technology of growing the trees and converting the trees. We’ve determined where it’s economically viable and where it isn’t. We’ve looked at environmental impacts, so there shouldn’t be any surprises.”
For more information about AHB Northwest, visit