Environmental Engineering Reference
In-Depth Information
be transformed into biodiesel via transesterification process through an alkaline
catalyst. Alterations in the process were administered to achieve a higher FFA
content in the biodiesel. Heterogeneous catalysts have been produced which can
lead to higher efficiency and convenient removal of glycerol and aqueous base
catalyst. Not much is discovered about the deleterious emission of biodiesel made
from vegetable oils. Much needs to be experimented on its clinical and economi-
cal attributes.
3.3 Bio-gas
With the rising population and urban development towards the millennium, air pol-
lution issues have touched the peak. As the number of vehicles on roads multi-
plied, so did the harmful emission in the atmosphere. The urgent need to reduce the
menacing emission for minimizing global warming was therefore the first catapult
objective behind the idea of biogas.
Biogas is by far the most versatile renewable resource that cannot only replace
fossil fuels for the use of vehicle engines but also for the use of heat and power pro-
duction (Fehrenbach et al. 2008 ). The production mechanism of biogas via anaero-
bic digestion provides environmental and energy-efficient advantages over other
energy sources. Methane gas is the first viable candidate for the major composition
of biogas since its early production.
3.3.1
Biochemical Process
Methane gas is fermented for obtaining it in colossal amounts. Its fermentation is a
perplex process, composing of distinct steps, namely, hydrolysis, dehydrogenation
and methanation (Angelidaki et al. 1999 ). The first step is hydrolysis using hydro-
lyzing microorganisms. These secrete hydrolyzing enzymes: cellulose, amylase and
lipase to breakdown the added monomers and polymers (Bagi et al. 2007 ). This
breakdown of polymers or monomers results in the production of acetate and hydro-
gen and some fatty acid derivatives like butyrate and propionate.
An exclusive nexus of microorganisms are added into the culture medium for
the production of methane gas. Of this consortium of microorganisms, mostly an-
aerobes are employed, such as Bacteriocides, Bifidobacteria and Clostridia. Some
facultative anaerobes can also be employed such as Streptococci and Enterobacte-
riacea (Bagi et al. 2007 ). Subsequent to hydrolysis of polymers, the methanogenic
bacteria produce methane gas using acetate and hydrogen molecules. When using
methanogenic bacteria, hydrogen production is easily achieved in two stages only
(Schink 1997 ).
The neighboring degradation steps of the anaerobic fermentation have to occur
in an equilibrium proportion, if it occurs at a faster rate, the pH will fall below 7,
putting the survival of the methanogenic bacteria in trouble. If the second step out
Search WWH ::




Custom Search