Environmental Engineering Reference
In-Depth Information
as, bio-oil and gas by thermochemical reaction while using biochemical reaction
for the production of ethanol, biodiesel and bio hydrogen (Kwiatkowski et al.
2006
;
Deirue et al.
2012
). The production of algal biomass is a lot more cost worthy than
the crops; this is because photosynthesis requires light, carbon dioxide, water, spe-
cific range of temperature (293-303 K) and inorganic salts. So in order to minimize
the expenses, the production of biodiesel must mainly rely on the free available
sunlight (Liu et al.
2012
). The benefits of consuming microalgae as a source of
production of biofuels are removal of carbon dioxide from industries and environ-
ment by algae bio-fixation, reducing the GHG emission while producing biodiesel,
allowing algae to develop as consumers of water wastes as nutrients present in
wastewater, for the removal of ammonium, nitrate, phosphate. The oil harvested
from the subsequent algae biomass can be processed into ethanol, methane, live-
stock feed, which can be useful as carbon-based fertilizer or energy cogeneration
(Chisti
2007
; Amin
2009
). Microalgae can produce high quality organic products
with numerous probable profitable claims. These can possibly transform a bulk of
biotechnological regions containing biofuels, pharmaceuticals, cosmetics, nutrition
and food flavors, aquaculture, and pollution avoidance (Raja et al.
2008
; Rosenberg
et al.
2008
; Wang et al.
2008
).
Some of the important microalgae culture systems are:
i.
Open culture system or ponds:
Open culture systems are the simplest and oldest technology used for the mass
cultivation of micro-algae, also called algae farms, possessing a raceway con-
figuration. They are usually made up of concrete or simple dug in the ground
and out lined using plastic, preventing the liquid from seeping into the ground.
The wheel paddle mixes and circulates the algal cells and nutrients. The system
is worked in unceasing style, fresh feed is continuously placed and algal broth is
harvested (Mata et al.
2010
). The water in open ponds is shallow, thus allowing
the algae exposure to sunlight. The efficiency is calculated in terms of biomass.
These ponds under proper pH control and other physical condition can utilize up
to 90 % of the waste CO
2
injected in the pond, thus helping in CO
2
fixation. The
efficiency is reduced by infection with unwanted algae and microbes that con-
sume algae. They increase the problems of land usage price, water accessibility
and climatic circumstances (Richmond
2004
; Mata et al.
2010
).
ii.
Photo bioreactors:
Photo bioreactors are closed arrangements in which algae are allowed to grow
(Richmond
2004
). They prevent direct fall out, avoiding chances of contamina-
tion but are expensive compared to open ponds. They have higher efficiency,
greater biomass concentration, short harvest time and higher face to volume ratio
than open ponds. The highest cost associated with closed arrangement is associ-
ated with energy price beside the mixing apparatuses (Richmond
2004
; Amin
2009
).
