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Green algae
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It 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.
To 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.
"My 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 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 team points out that shorter
reaction times mean that the reactors don't have to be as large.
"By 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.
Current 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.
Before 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.
Once producing 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.
The research, "The Effects of
Heating Rate and Reaction Time on Hydrothermal Liquefaction of
Microalgae," was funded by the Emerging Frontiers in Research
and Innovation program of the National Science Foundation. The
university is pursuing patent protection for the intellectual
property, and is seeking commercialization partners to help bring the
technology to market.
Savage
Lab: http://savageresearchlab.wordpress.com
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