Algae Crops: Coproduction of Algae Biofuels - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 368

[ 32 ]. Instead of light and photosynthesis, heterotrophic algae use carbon

sources [ 33 ].
The traditional alternative employs open pond systems. The open pond system
uses a shallow pond (~1 m deep) in which algae are cultivated. Nutrients are
provided through runoff water or by channeling the water from sewage/water
treatment plants [ 34 ]. Many studies and several commercial plants have demon-
strated the profitability of sewage and wastewater treatment [ 35 , 36 ]. Oxygen
production by microalgae for waste oxidation by bacteria in ponds is one example.
Others include disinfection, nutrients, and the removal of heavy metals and organic
toxins. To this end, Oswald estimates that the saving associated with use of algae
instead of electricity for oxygen production in sewage ponds to be between 3,300
and 14,000 US$ per hectare (assuming energy price of 10 cents per kilowatt
an hour).
Algae provide oxygen for the bacterial breakdown of the wastes, which in the
absence of algae would be achieved using conventional processes of mechanical
aeration. The challenge, however, is to harvest the algal biomass; such techniques
are only practical using large-scale ponds. Algae are relatively efficient at capturing
and removing nutrients, such as N and P. Thus, when wastewater treatment
expanded from just oxidizing the organic matter to removing nutrients, it increased
interest in employing algae for this purpose.
There is a lot of potential in combining microalgae with waste management as
well as other activities [ 34 , 37 ]. Furthermore, many of the waste management
technologies developed using microalgae are appropriate for algal use for other
production activities—the case of the Arava, Israel, and the production of
β

-carotene are just two examples.

Algae Bioenergy

Algae are used to produce bioenergy—i.e., renewable energy made available from
materials derived from biology. The use of algae to produce energy has spurred
investment by several sectors, some focusing on biodiesel, while other on green
gasoline and drop-in fuels.

Recent Trends in Macroalgae Energy Production

Recently, there is rising investment from petrochemical majors, and governments
aimed at using seaweed for ethanol, advanced biofuels, drop-in fuels, biochemical,
and biopolymers. A recent study (executive summary is available at http://pdf.pr.
com/press-release/pr-266157.pdf ) suggests macroalgae has potential to become an
energy feedstock. That study details emerging projects in macroalgae (Table 17.1 ).