Alternative fuels and green aviation - Biomass as Energy Source: Resources, Systems and Applications - page 202

wild in Florida (Gordon et al. , 2011). In spite of these criticisms, there may be a role for jatropha
as a biofuel feedstock in some geographical locations, in part because plantations have already
been established.
Castor beans are related to jatropha, but are less toxic, and still have a lipid content of 40-60%.
Castor-derived biodiesel blends may provide better lubricity than that of other vegetable oils,
even at very low concentrations of less than 1% (Goodrum and Geller, 2004). This is likely due
to the fact that castor oil contains high quantities of ricinoleic acid (C 18 H 34 O 3 ), an unsaturated
ω 9 fatty acid, and trace amounts of dihydroxystearic acid (C 18 H 36 O 4 ), which have more hydroxyl
groups (1 and 2, respectively) than most vegetable oils (Refaat, 2009). Evogene, an Israeli
company, is systematically breeding castor plants for good oil production potential. Biodiesel
created from Evogene's castor has been produced by UOP, with testing by the US Air Force
and NASA. Preliminary characterization of castor-based biodiesel indicates that the hydrocarbon
composition has substantial content in the C9-C11 range (Bruno and Baibourine, 2011) and looks
promising for meeting the standards required for aviation fuel.
For further reading on other types of vegetable oils under consideration as biofuel feedstocks,
see Balat (2011b), Holser and Harry-O'Kuru (2006), Kumar et al. (2010), Razon (2009), and
Singh and Singh (2010).

11.4.2 Crop production for oil from algae
Third-generation feedstocks may be obtained from algae, cyanobacteria and halophytes. Algae
are photosynthetic organisms that span length scales from just a few microns (unicellular micro-
algae) up to 50m (multicellular macroalgae, such as kelp). Cyanobacteria are also photosynthetic
organisms, but, unlike algae, thesemicrobes lack amembrane-bound nucleus. Halophytes are salt-
tolerant plants, such as salt marsh grass, that can thrive in saltwater. There is a huge environmental
benefit to growing saltwater-tolerant halophytes and microbes (Yang et al. , 2011), because they
can be nourished from seawater or brackish water rather than freshwater. Algae are also an attrac-
tive crop because they can sequester carbon by using the flue gas from power plants as a nutrient
source and remediate wastewater. In this section, we will limit the discussion to algae. For reading
on cyanobacteria, see Bouriazos et al. (2010), Quintana et al. (2011), Tan et al. (2011); and for
halophytes, see Hendricks (2008), Hendricks et al. (2011), and McDowell Bomani et al . (2009).
Oleaginous (oil-producing) algae have been hailed as the most efficient producers of green
crude over all feedstock types - potentially. The cost-effective growth of algae for conversion to
biofuel in a production-scale setting has not yet been achieved, but there are many companies that
are currently building such facilities. For a listing of commercial facilities for algae growth, see
Singh and Gu (2010) as a starting point, but note that their data, based on a 2009 study, is already
obsolete (!), and many more are in process.
From 1978 to 1996, the US Department of Energy funded the Aquatic Species Program (ASP)
to quantitatively explore the concept of producing biodiesel from algae. The program analyzed
over 3000 strains of microalgae and diatoms (algae with a cell wall of silica), which were narrowed
down to the 300 most promising microbes. The intent was not only to understand which species
were the best at oil production, but also their hardiness with respect to seasonal temperature
variation, pH, and salinity, and the ability to outgrow wild competitors, all of which affect the
stability of the culture. Algal growth in industrial-scale open ponds with 1000m 2 surface area
was examined for feasibility of mass production in California, Hawaii and NewMexico (Sheehan
et al. , 1998). As is typical of open-pond aquaculture, the depth of the ponds was shallow to aid in
light penetration, here 10-20 cm. TheASP determined that microalgae use far less water and land
than oil-producing seed crops, estimating that 200,000 hectares could produce significantly more
energy than seed crops, about one quadrillion BTUs of energy (

10 18 Joules, or roughly 1%
of global energy consumption). Nevertheless, the ASP concluded that biofuel from algae would
not be cost-competitive with petroleum fuel. In their 1995 evaluation, they projected the cost of
algae-based biofuel to be 59-186 US$/bbl versus petroleum at $20/bbl. Since then, the gap has
likely narrowed due to adjustments on both types of fuel.

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