Seaweeds: A Promising Source for Sustainable Development - Environmental Sustainability: Role of Green Technologies - page 81

If the annual biomass production capacity is
increased to 10,000 t, the cost of production per
kilogram reduces to roughly $ 0.47 and $ 0.60 for
photobioreactors and raceways, respectively,
because of economies of scale. Assuming that the
biomass contains 30 % oil by weight, the cost of
biomass for providing a liter of oil would be
something like $ 1.40 and $ 1.81 for photobiore-
actors and raceways, respectively (Chisti 2007 ).
Biodiesel from palm oil costs roughly $ 0.66/L,
or 35 % more than petrodiesel. This suggests that
the process of converting palm oil into biodiesel
adds about $ 0.14/L to the price of oil. For palm
oil-sourced biodiesel to be competitive with pet-
rodiesel, the price of palm oil should not exceed
$ 0.48/L, assuming no tax on biodiesel. Using
the same analogy, a reasonable target price for
microalgal oil is $ 0.48/L for algal diesel to be
cost competitive with petrodiesel.

It has been estimated that 0.53 billion m 3 of
biodiesel would be needed to replace current US
transportation consumption of all petroleum fuels
(Chisti 2007 ). Neither waste oil nor seed oil can
come close to meeting the requirement for that
much fuel; therefore, if biodiesel is to become a
true replacement for petroleum, a more productive
source of oil such as algal oil is needed (Scott and
Bryner 2006 ; Chisti 2007 ). The cost of producing
microalgal biodiesel can be reduced substantially
by using a biorefi nery-based production strategy,
improving capabilities of microalgae through
genetic engineering and advances in photobioreac-
tor engineering. Like a petroleum refi nery, a biore-
fi nery uses every component of the biomass raw
material to produce usable products (Chisti 2007 ) .

11 Utilization of Seaweeds

in Wastewater Treatment

10.2 Improving Economics

of Microalgal Biodiesel

11.1 Seaweeds in Sewage

Treatment

Algae are among the fastest growing plants in the
world, and about 50 % of their weight is oil.
That lipid oil can be used to make biodiesel for
cars, trucks, and airplanes. Algae will someday
be competitive as a source of biofuel. Only
renewable biodiesel can potentially completely
displace liquid fuels derived from petroleum. The
economics of producing microalgal biodiesel
need to improve substantially to make it competitive
with petrodiesel, but the level of improvement
necessary appears to be attainable (Demirbas
2008 ). Biodiesel has great potential; however, the
high cost and limited supply of renewable oils
prevent it from becoming a serious competitor
with petroleum fuels. As petroleum fuel costs rise
and supplies dwindle, biodiesel will become
more attractive to both investors and consumers.
For biodiesel to become the alternative fuel of
choice, it requires an enormous quantity of cheap
biomass. Using new and innovative techniques
for cultivation, algae may allow biodiesel produc-
tion to achieve the price and scale of production
needed to compete with, or even replace, petro-
leum (Campbell 2008 ).

Wastewater stabilization ponds are designed
for anaerobic and aerobic bacteria and algae to
decompose waterborne organic wastes effi ciently.
Ludwig et al. ( 1951 ) studied the role of algae in
the treatment of sewage by photosynthetic oxy-
genation in waste stabilization ponds. Indian
coastal waters are constantly polluted with indus-
trial and domestic wastes. Domestic sewage is
rich in nutrients such as NH 4 -N, NO 2 -N, NO 3 ,-N,
PO 4 -P, K, etc. The discharge of sewage into the
coastal waters is estimated to be 35 Km 3 /year
(Qasim and Sen Gupta 1988 ). Addition of such
enormous quantities of pollutants into the coastal
water affects its water quality and cause eutrophi-
cation. Therefore, treatment of wastewaters
before their discharge into the sea is essential.
Red seaweeds like Chondrus crispus , Gracilaria
foliifera , and Neoagardhiella baileyi when grown
in the aquaculture system considerably removed
the nutrients (Ryther et al. 1979 ). Dhargalkar ( 1986 )
observed that Ulva fasciata and G. verrucosa
showed better growth in 5 % sewage seawater
mixture. The biomass of Ulva sp . and Enteromorpha
sp . increased when they were grown near the