Governors' Biofuels Coalition

The next generation of biofuels will come from the sugars in agricultural residues, switch grass, poplar trees and city trash.

But advanced biorefineries today work best with a single feedstock, and they depend on its year-round availability. That’s a problem.

“It doesn’t take a rocket scientist to see that that might not be the case out in the real world,” said Blake Simmons, a researcher at the San Francisco-based Joint Bioenergy Institute and a co-author of a new feedstock study in Biofuels. Biorefineries “need to be able to manage mixtures of feedstocks that are available year-round.”

Simmons and researchers at the institute and the Idaho National Laboratory think they may have found the answer. They blended four feedstocks — lodgepole pine, eucalyptus, corn stover and switch grass — into pellets and then subjected the pellets to pretreatment.

The sugars that came out of the pellets were the same regardless of how the four feedstocks were fed into the process, and the fuel yields equaled those of single feedstocks. The results indicate that the pretreatment method could be used for any mix of feedstocks — essentially guaranteeing biorefineries a feedstock regardless of growing seasons or whatever Mother Nature throws their way.

“We’re changing the paradigm of the existing biorefinery model,” said Kevin Kenney, a research engineer at the Idaho lab who was not part of the study. “The existing is selecting a location where there is a single abundant supply of a single plant. But biorefineries can be sited based on aggregate supply.”

The research goal, Simmons said, is “McTreatment.”

“We want to franchise pretreatment techniques that you can put anywhere in the world,” he said. “That kind of standardization we think would really de-risk the development of both pilot- and commercial-scale refineries. You don’t have to worry about an ideal feedstock. I can take anything and generate sugars, and can take those sugars and generate fuels.”

A big part of the process is getting hay and other cellulosic feedstocks into smaller, more dense forms that maximize energy per unit. Idaho National Laboratory has led the nation on research into pelletizing biofuels inputs.

Once the inputs are in that form, another key is the pretreatment process that uses “ionic liquids.”

Ionic liquids have been used in other industries for years. An offshoot of the green chemistry movement in the late 1970s, the liquids potentially could be used in a variety of products, from organic solvents to batteries, according to Simmons. In the biofuels process, they break down the tough lignocellulosic components of plants so they can be easily fermented into fuels.

There may be other pretreatments that work better for different blends of feedstocks, but so far, ionic liquids seem ideal for blended feedstocks, Simmons said, though high costs remain a drawback.

“It’s still a nascent field within the biofuels community, but I think it’s very promising,” he said.

While a few companies have expressed interest in the technology being developed by the researchers, it will likely take at least five years before it becomes mainstream. More research needs to be done on other blends of feedstocks and determining the economics of the different qualities and quantities of various feedstocks throughout the country.

The researchers say blending feedstock is critical to advanced biofuel development.

“There are places that may have a lot of biomass, but it’s different kinds,” said Vicki Thompson, a co-author of the study. “In order to get enough, you’re going to have to combine them.”

 

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