Heating and squishing microalgae in a pressure-cooker can fast-forward the crude-oil-making process from millennia to minutes.
U-M professors are working to understand and improve this procedure in an effort to speed up development of affordable biofuels that could replace fossil fuels and power today’s engines.
Peigao Duan, a graduate student in professor Phillip Savage’s lab, holds a vial of bio-oil. Photo by Nicole Casal Moore.
They also are examining the possibility of other new fuel sources such as E. coli bacteria that would feed on waste products from previous bio-oil batches.
“The vision is that nothing would leave the refinery except oil. Everything would get reused. That’s one of the things that makes this project novel. It’s an integrated process. We’re combining hydrothermal, catalytic and biological approaches,” says Phillip Savage, an Arthur F. Thurnau Professor in the Department of Chemical Engineering and principal investigator on the $2-million National Science Foundation grant that supports this project. The grant is funded under the American Recovery and Reinvestment Act.
“This research could play a major role in the nation’s transition toward energy independence and reduced carbon dioxide emissions from the energy sector,” Savage says.
Microalgae are microscopic species of algae: simple, floating plants that don’t have leaves, roots or stems. They break down more easily than other potential biofuel source plants because they don’t have tough cell walls, Savage says.
Unlike fossil fuels, algae-based biofuels are carbon-neutral. The algae feed on carbon dioxide in the air, and this gets released when the biofuel is burned. Fossil fuel combustion puffs additional carbon into the air without ever taking any back.
Researchers heat algae in a device that acts like a pressure cooker to turn the algae into a crude bio-oil. They are working to improve this procedure in an effort to speed up development of affordable biofuels that could replace fossil fuels and power today’s engines. Photo by Nicole Casal Moore.
The pressure-cooker method the researchers are studying bucks the trend in algae-to-fuel processing. The conventional technique involves cultivating special, oily types of algae, drying the algae and then extracting its oil.
The hydrothermal process this project employs allows researchers to start with less-oily types of algae. The process also eliminates the need to dry it, overcoming two major barriers to large-scale conversion of microalgae to liquid fuels.
“We make an algae soup,” Savage says. “We heat it to about 300 degrees and keep the water at high enough pressure to keep it liquid as opposed to steam. We cook it for 30 minutes to an hour and we get a crude bio-oil.”
The high temperature and pressure allows the algae to react with the water and break down. Not only does the native oil get released, but proteins and carbohydrates also decompose and add to the fuel yield.
“We’re trying to do what nature does when it creates oil, but we don’t want to wait millions of years,” Savage says.
Savage and his colleagues are investigating ways to use catalysts to bump up the energy density of the resulting bio-oil, thin it into a flowing material and also clean it up by reducing its sulfur and nitrogen content.
Other collaborators are Gregory Keoleian, professor of sustainable systems in the School of Natural Resources and Environment and in the Department of Civil and Environmental Engineering; Adam Matzger, professor in the Department of Chemistry; Suljo Linic, assistant professor in the Department of Chemical Engineering; Nina Lin, assistant professor in the Department of Chemical Engineering and Department of Biomedical Engineering; Nancy Love, professor and chair of the Department of Civil and Environmental Engineering; and Henry Wang, professor in the Department of Chemical Engineering and Department of Biomedical Engineering.
