October 31, 2012
looks like Mother Nature was wasting her time with a multimillion-year
process to produce crude oil. Michigan Engineering researchers can
"pressure-cook" algae for as little as a minute and transform an
unprecedented 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 findings will be presented Nov. 1 at the 2012 American Institute of Chemical Engineers Annual Meeting in Pittsburgh.
Savage's ocean-going organism of choice is the green marine micro-alga of the genus Nannochloropsis.
make their one-minute biocrude, Savage and Julia Faeth, a doctoral
student in Savage's lab, filled a steel pipe connector with 1.5
milliliters 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 with only a minute to warm up, the algae's temperature
should have just grazed the 550-degree mark before the team pulled the
reactor back out.
Previously, Savage and his team heated the
algae for times ranging from 10 to 90 minutes. They saw their best
results, with about half of the algae converted to biocrude, after
treating it for 10 to 40 minutes at 570 degrees.
Why are the
one-minute results so much better? Savage and Faeth won't be sure until
they have done more experiments, but they have some ideas.
guess is that the reactions that produce biocrude are actually must
faster than previously thought," Savage said. Faeth suggests that the
fast heating might boost the biocrude by keeping unwanted reactions at
"For example, the biocrude might decompose into substances
that dissolve in water, and the fast heating rates might discourage
that reaction," Faeth said.
The team points out that shorter reaction times mean that the reactors don't have to be as large.
reducing the reactor volume, the cost of building a biocrude
production plant also decreases," Faeth said, though both she and Savage
cautioned that they couldn't say for sure whether the new method is
faster and cheaper until the process is further developed.
commercial makers of algae-based fuel first dry the algae and then
extract the natural oil. But at over $20 per gallon, this fuel is a
long way from the gas pump.
"Companies know that that approach
is not economical, so they are looking at approaches for using wet
algae, as are we," Savage said.
One of the advantages of the
wet method is that it doesn't just extract the existing fat from the
algae—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.
biocrude can be fed into the existing refinery system for petroleum,
it needs pre-refining to get rid of the extra oxygen and nitrogen atoms
that abound in living things. The Savage lab also is 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. A
paper on this work is currently under review.
biofuel from algae is economical, researchers estimate that an area the
size of New Mexico could provide enough oil to match current U.S.
petroleum consumption. And, unlike corn produced for ethanol—which
already accounts for half that area—the algae won't need to occupy good
farmland, thriving in brackish ponds instead.
information: The Effects of Heating Rate and Reaction Time On
Hydrothermal Liquefaction of Microalgae,
Provided by University of Michigan