Two biofuels produced from single algae

About algae

Algae are simple plants that can range from the
microscopic (microalgae), to large seaweeds (macroalgae), such as giant kelp
more than one hundred feet in length. Microalgae include both cyanobacteria,
(similar to bacteria, and formerly called “blue-green algae”) as well as green,
brown and red algae. (There are more varieties of microalgae, but these are the
main ones.) Algae can be grown using water resources such as brackish-, sea-,
and wastewater unsuitable for cultivating agricultural crops. When using
wastewater, such as municipal, animal and even some industrial runoff, they can
help in its treatment and purification, while benefiting from using the
nutrients present. Most microalgae grow through photosynthesis – by converting
sunlight, CO2 and a few nutrients, including nitrogen and phosphorous, into
material known as biomass This is called “autotrophic” growth. Algae are very
diverse and found almost everywhere on the planet. They play an important role
in many ecosystems, including providing the foundation for the aquatic food
chains supporting all fisheries in the oceans and inland, as well as producing
about 70 percent of all the air we breathe.
Two biofuels from single
algae

A common algae commercially grown to make fish food
holds promise as a source for both biodiesel and jet fuel, according to a new
study published in the journal Energy & Fuels. The researchers, led by Greg
O’Neil of Western Washington University and Chris Reddy of Woods Hole Oceanographic
Institution, exploited an unusual and untapped class of chemical compounds in
the algae to synthesize two different fuel products, in parallel, a from a
single algae. “It’s novel,” says O’Neil, the study’s lead author.
“It’s far from a cost-competitive product at this stage, but it’s an
interesting new strategy for making renewable fuel from algae.”
Researchers Greg O’Neil, right, of Western Washington
University and Chris Reddy of Woods Hole Oceanographic Institution, exploited
an unusual and untapped class of chemical compounds in the algae to synthesize
two different fuel products, in parallel, a from a single algae. Credit: Tom
Kleindinst, Woods Hole Oceanographic Institution.

Algae contain fatty acids that can be converted into
fatty acid methyl esters, or FAMEs, the molecules in biodiesel. For their
study, O’Neil, Reddy, and colleagues targeted a specific algal species called
Isochrysis for two reasons: First, because growers have already demonstrated
they can produce it in large batches to make fish food. Second, because it is
among only a handful of algal species around the globe that produce fats called
alkenones. These compounds are composed of long chains with 37 to 39 carbon
atoms, which the researchers believed held potential as a fuel source. Biofuel
prospectors may have dismissed Isochrysis because its oil is a dark, sludgy
solid at room temperature, rather than a clear liquid that looks like cooking
oil. The sludge is a result of the alkenones in Isochrysis—precisely what makes
it a unique source of two distinct fuels.
Alkenones are well known to oceanographers because they
have a unique ability to change their structure in response to water
temperature, providing oceanographers with a biomarker to extrapolate past sea
surface temperatures. But biofuel prospectors were largely unaware of
alkenones. “They didn’t know that Isochrysis makes these unusual compounds
because they’re not oceanographers,” says Reddy, a marine chemist at WHOI.
Reddy and O’Neil began their collaboration first by making biodiesel from the
FAMEs in Isochrysis. Then they had to devise a method to separate the FAMEs and
alkenones in order to achieve a free-flowing fuel.The method added steps to the
overall biodiesel process, but it supplied a superior quality biodiesel, as
well as “an alkenone-rich . . . fraction as a potential secondary product
stream,” the authors write.

“The alkenones themselves, with long chains of 37
to 39 carbons, are much too big to be used for jet fuel,” says O’Neil. But
the researchers used a chemical reaction called olefin metathesis (which earned
its developers the Nobel Prize in 2005). The process cleaved carbon-carbon
double bonds in the alkenones, breaking the long chains into pieces with only 8
to 13 carbons. “Those are small enough to use for jet fuel,” O’Neil
says. The scientists believe that by producing two fuels—biodiesel and jet
fuel—from a single algae, their findings hold some promise for future
commercialization. They stress that this is a first step with many steps to
come, but they are encouraged by the initial result. “It’s scientifically
fascinating and really cool,” Reddy says. “This algae has got much
greater potential, but we are in the nascent stages.” (Source: Phys.org)

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