There are a variety of other challenges to developing economical,
high-performance biofuels. The first set of challenges involves
logistics. While biomass resources are located across the country,
what is needed is high concentrations of biomass so biofuel production plants can achieve economies of scale that will reduce
biofuel costs without shipping raw materials over long distances.
A second challenge is developing preconversion technology to
reduce biomass physical volume and moisture content. A third
challenge is blending different biomass resources — again with
the goal of achieving economies of scale. A fourth challenge is
biomass conversion, in which chemists working in biorefineries
use moderate temperature and pressure to produce stable, consistent fuel products.
University scientists are investigating potentially improved process
technologies to more efficiently use algae and energy to produce
biofuels. For example, Lindsay Soh of Yale University has performed
life-cycle analysis of a single-step lipid extraction — a transesterifi-cation process using supercritical CO2 and methanol. Soh evaluated
both basic and acidic heterogeneous catalysis to produce fatty acid
methyl esters (FAME). Enhanced solubility of FAME compared with
reaction intermediates provides a driving force for the reaction,
promoting high conversion to the desired FAME molecules.
Another concern is water consumption needed to grow algae.
Most of the current development involves growing selected
strains of algae in open ponds or closed photobioreactors using
various water sources, collecting and extracting the oil from
algae, or collecting fuel precursors secreted by algae, and then
processing the oil into fuel.
Research reported in late 2012 addresses concerns over fresh-
water supply for algae production. Stephen Mayfield, a University
of California at San Diego professor, reported last November that
saltwater algae can be just as capable as freshwater algae in pro-
ducing biofuels. “Once you can use ocean water, you are no lon-
ger limited by the constraints associated with freshwater. Ocean
water is simply not a limited resource.”
The availability of significant saltwater environments for
algae production has been documented in recent years. Accord-
ing to a Pacific Northwest National Laboratory report, saltwater
algae can also be grown using saline water from existing aqui-
fers. “There are about 10 million acres of land across the United
States where crops can no longer be grown that could be used to
produce algae for biofuels. Marine species of algae tend to toler-
ate a range of salt environments, but many freshwater species
don’t tolerate any salt in the environment,” comments Mayfield.
Additional plants are also being evaluated as raw materials
for renewable fuels. For example, Glenn Miller and his co-workers
at the University of Nevada have evaluated Grindelia squarrosa
(gumweed), a biennial flowering plant common to Nevada and
other areas of the arid western United States. It appears to be a
strong candidate to be a biofuel feedstock, producing an average
of 12–23% crude oil by dry weight.
PHO TOS COURTESY OF THE U. S. NAV Y
TOP: As part of the RIMPAC exercise, an F- 18 jet fighter was powered
BOTTOM: On a voyage from San Diego, CA, to Bremerton, WA, the
USS Ford was powered by biofuel.
While most hydrocarbons present in the acetone extracts in
this crude oil are at the heavy end of diesel fuel, a methylated B20
blended biodiesel was shown to meet industry standards for flash
point, kinematic viscosity, and sulfur content. Gumweed can produce biocrude oil at an annual rate of 60–100 gallons per acre.
Speaking during the RIMPAC tests, Lieutenant Commander Kim
said, “It’s going to be pretty amazing to see where these fuels take
us in the future. This might be the largest demonstration to date,
but it is not the last.” Given the R&D underway at many industrial,
government, and academic labs, fuels used in the next round of
tests, which could occur in 2016, may be next-generation versions
of today’s leading-edge biofuels.
John K. Borchardt was a chemist, freelance writer, and devoted ACS career consultant for more than 15 years, until his sudden passing in January 2013. He was the author of the ACS/Oxford University Press book Career Man- agement for Scientists and Engineers, and also had more than 1500 articles published in a
variety of magazines, newspapers, and ency-
clopedias. As an industrial chemist, he held 30 U.S. and more than
125 international patents and was the author of more than 130
peer-reviewed papers. John’s advice, insights, and articles helped
countless scientists improve their professional lives, and he will be
inChemistry • www.acs.org/undergrad