Biomedical Engineering Reference
In-Depth Information
microalgae for biofuel production. Photosynthetic production of algal biomass can
be enhanced by an extraneous enrichment with CO
2
;
industrial effluents containing
CO
2
can be utilized to sustain high algal productivity (Raven, 2009; Benemann, 1993).
This could help a nation lower its emissions of greenhouse gases and could be used
for carbon tax credit. The International Energy Agency (IEA) estimated that biofuels
contribute to approximately 2
%
of global transport fuel today but could increase to
27
%
by the year 2050. They project that if biofuel production is sustained, it could
displace enough petroleum to avoid the equivalent of 2.1 Gt y
−1
CO
2
emission—
comparable to the net CO
2
absorbed by the oceans calculated by Fairley (2011).
The algae-to-biotechnology framework has five stages—that is, algal cultiva-
tion, biomass harvesting, algal oil extraction, oil residue conversion, and by-product
distribution—and each has several composite processes (Natural Resources Defense
Council, 2009). Given the vast potential of microalgal biotechnology, many entre-
preneurs focus largely on algal biomass as a source of biofuel rather than high-value
chemicals such as nutraceuticals and pharmaceuticals. For example, by the end
of this decade, the projected worldwide market value of carotenoids alone will be
US$1,000 million (Del Campo et al., 2007). Some of the co-products fetch higher
prices; for example, astaxanthin is about 3,000 times more expensive than the
$1,000-per-ton crude oil (Cysewski and Lorenz, 2004). Although the payoffs for entre-
preneurs are attractive, building biotech businesses based on a new, unproven technol-
ogy poses more formidable challenges. Continuous production of vast quantities of
algal biomass under optimal conditions is crucial in sustaining economically viable
biofuel technology. Although fifty algal biofuel companies exist (http://aquaticbiofuel.
com/2008/12/05/2008-the-year-of algae-investments/.), production on a commercial
scale at competitive prices has not yet taken place (Pienkos and Darzins, 2009; St.
John, 2009). One of the biggest challenges to commercial algal operations is to trans-
late laboratory conditions to large scale, and most companies operate in “stealth”
mode (Natural Resources Defense Council, 2009). To make it cost effective, Wijffels
(2007) suggested that production costs must be reduced up to two orders of magni-
tude. When operating an algal biofuel production facility, plans should be in place
to tackle unforeseen exigencies such as weather changes, and crashing of algal
populations that could disrupt production and cause huge losses. As microalgae are
renewable, sustainable, and affordable, their potential to produce biofuels is great
if the current practices are cost competitive with petroleum diesel. Improvements
in harvesting practices, extraction of biofuels, and conversion to co-products could
bring down the production costs. Here we discuss the need to optimize various ele-
ments such as algal strains, cultivation, production costs, lipid variations, harvesting
biomass, and genetic modification of microalgae to make microalgal biotechnology
economically viable.
13.2 CULTIVATION
Approximately fifty species are utilized in biotechnology, mostly as biofeed. In these
“traditional” species, manipulations of culture conditions (i.e., temperature, light,
and nutrients) dramatically influence the yield of biomass. Long-term maintenance of
algae may result in loss of algal vigor, resulting in “culture crashes” (Russell, 1974).
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