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The Race for Green Gasoline
Pyrolysis is the next hot area for biofuels research
UMass Amherst Chemical Engineering Profesor Paul Dauenhaur with bio-oil vial.

UMass Amherst is making ground-breaking ‘green gasoline’ a reality.

Our greener future, according to Paul Dauenhauer, chemical engineering, can be found in the orange glow of a campfire. For years, fuel production research has focused on corn and soybeans (leading to ethanol and biodiesel), and before that, on synthetic fuels.

In the last 10 years, the most promising technology—pyrolysis (literally meaning “to break apart with fire”)—has gained the attention of top biofuel research groups. With the prestigious, $800,000 Early Career Award in Basic Energy Sciences from the U.S. Department of Energy (DOE), Dauenhauer is gaining attention for his studies of the thermal degradation of wood. 

As wood heats, its molecules get smaller, and when they mix with air, that familiar orange glow results. The wood turns into hundreds of chemicals, the biggest groupings being furans, anhydrosugars, and aldehydes. These chemicals can be collected from wood as a brown crude, or ‘bio-oil’, of which a certain portion can be upgraded to bio-fuels.

If you look at wood, you will see both white and dark regions of the grain. The white parts are long chains of sugars, and when they break during thermal degradation, they fracture in certain patterns. “If we understand how wood pyrolyzes,” says Dauenhauer, “we can control the reaction to degrade in the most favorable way to make ‘green gasoline.’ ”

In the best conditions, 70 percent of biomass, such as wood chips, can be converted into bio-oil, which is subsequently upgraded in a biorefinery to green gasoline. However, unlike petroleum, which comes out of the ground, bio-oil composition is controlled by the pyrolysis process, and higher quality bio-oils result in greater yields of green gasoline. “There are perhaps only a couple of universities that are as intensely focused in the pyrolysis area of biofuels as UMass Amherst,” says Dauenhauer. “The race is on,” he adds, “to predict which pyrolysis reactions produce high quality bio-oils and greater quantities of biofuel.” 

Brought on board in 2009, Dauenhauer is using a hybrid poplar tree for thermal degradation—it grows fast. He is particularly excited to be located among the biomass-rich woodlands of Western Massachusetts. “New England is the burgeoning biofuel center,” he says. “The new generation of biomass crops are wood and grasses, which situates UMass Amherst prominently. All we need now is the technology.” With the help of this award, that’s fast coming. Dauenhauer and colleagues have published new findings in Science describing how they combined high-speed photography of heated cellulose with theoretical fluid modeling to uncover a plausible mechanism for ejection of certain non-volatile compounds in the pyrolysis product stream. The process, called reactive boiling ejection, describes how bubbles form and then quickly collapse in a short-lived molten cellulose phase. The collapse expels streams of aerosols that contain nonvolatile material. According to the Dauenhauer and his colleagues, a deeper understanding of this process should lead to more control over product distributions.

The award for Dauenhauer’s latest work comes on the heels of $80,000 in NSF support and the highly selective 3M Nontenured Faculty Award, which supports a three-year study of hybrid production of biorenewable aromatic chemicals. Dauenhauer’s DOE and 3M studies are spinoffs from his much-publicized research into a new method of gasification for converting biofuel feedstock into sustainable fuel, which, according to Technology Review, could have a “profound” effect on the chemical industry. His gasification process would not only greatly reduce greenhouse gas emissions, but also double the amount of fuel that can be made from an acre of biomass feedstock. Between Dauenhauer’s work on pyrolysis and other bio-fuels research across campus, UMass Amherst is making ground-breaking ‘green gasoline’ a reality.

David Bartone, '12G