November 1, 2012
Turning Algae To Biofuel In A Minute
Lee Rannals for redOrbit.com - Your Universe Online
Engineers from the University of Michigan have pulled off a feat in a matter of minutes that takes Mother Nature millions of years.
The researchers "pressure cooked" algae for as little as a minute and transformed 65 percent of the green slime into biocrude.
"We're trying to mimic the process in nature that forms crude oil with marine organisms," said Phil Savage, an Arthur F. Thurnau professor and a professor of chemical engineering at the University of Michigan.
The team filled a steel pipe connector with 0.05 ounces of wet algae, capped it and plunged it into 1,100-degree Fahrenheit sand.
The small volume ensured that the algae was heated through, but only with a minute to warm up. This enabled the algae's temperature to just graze the 550-degree mark before the team pulled the reactor back out.
The researchers previously heated the algae four times ranging from 10 to 90 minutes. They saw their best results, before the minute mark, was that about half of the algae converted to biocrude after being treated 10 to 40 minutes at 570 degrees.
Savage and colleagues aren't sure why exactly the method worked even better at just one minute.
"My guess is that the reactions that produce biocrude are actually must faster than previously thought," Savage said.
Julia Faeth, a doctoral student in Savage's lab, said the fast heating might boost the biocrude by keeping unwanted reactions at bay.
"For example, the biocrude might decompose into substances that dissolve in water, and the fast heating rates might discourage that reaction," Faeth said.
The researchers say that shorter reaction times mean that the reactors do not have to be as large.
"By reducing the reactor volume, the cost of building a biocrude production plant also decreases," Faeth said.
The scientists said they couldn't be sure whether the new method is faster and cheaper until the process is further developed.
Commercial algae-based fuel makers first dry the algae, then extract the natural oil. However, this can cost $20 per gallon and isn't exactly economical yet.
"Companies know that that approach is not economical, so they are looking at approaches for using wet algae, as are we," Savage said.
Using wet algae means it doesn't just extract from the existing fat from the algae, but it also breaks down proteins and carbohydrates. The minute method did this so successfully that the oil contained about 90 percent of the energy in the original algae.
"That result is near the upper bound of what is possible," Savage said.
Biofuel must be pre-refined to get rid of the extra oxygen and nitrogen atoms before biocrude can be fed into the existing refinery system for petroleum.
The scientists are developing better methods for this leg of biofuel production, breaking the record with a biocrude that was 97 percent carbon and hydrogen earlier this year.
The researchers estimate that an area the size of New Mexico could provide enough oil to match current U.S. petroleum consumption.