Environmental Engineering Reference
In-Depth Information
fungi can be evaluated in this direction. In this procedure two technologies are
used: (1) direct microbial transformation method and (2) enzymatic transforma-
tion method. It has numerous advantages like less cost, insignificant conditions
needed and improved yields (Luque et al.
2010
).
c.
Fermentation:
The process of fermentation comprises of microbes which consume sugar as
food and in the process lead to the production of bioethanol and other varieties
of products. The microbes are termed as the ethanologens, as these convert a
portion of sugar to ethanol. The microorganisms used are compatible with the
fermentation conditions i.e. pH, temperature, growth rate, tolerance to inhibi-
tory compounds, output result, osmotic tolerance, specificity, yield, stability etc
(Luque et al.
2010
). The fermentation can be done in batch, fed batch and con-
tinuous process. The selection of the method depends on properties of microbes
and nature of lignocellulosic hydrolysate other than economic aspects. Fed batch
containers are extensively used on the industrial level since they have both the
benefits of batch and continuous process. The key benefit when compared to
batch is, ability to increase the cell viable concentration, longer culture life and
more product accumulation (Luque et al.
2010
).
d.
Product and Solid recovery:
Fermentation products are unstable, so distillation is widely used equipment for
the recovery of the bioethanol and other products from a number of impurities.
The distillation separates bioethanol from water; the virgin ethanol has 80 %
water in it. Large amount of energy is needed for the concentration of bioethanol
to 95.6 % (Luque et al.
2010
). At first bioethanol is recovered from water which
has high moisture content. The bioethanol (37 %) is concentrated in the rectify-
ing column and is adjusted below a zeotrope, reaching 95 %. The residual prod-
uct is fed to stripping column for the removal of extra water (Luque et al.
2010
).
Bioethanol is recovered in the distillation unit which is stabilized to be about
99.6 % to lessen the bioethanol loss (Garcia et al.
2008
). Solids are dispersed by
centrifuge and dried over rotary dryer. About 25 % waste is reprocessed to fer-
mentation while the remaining is sent to evaporator. The concentrated solution
comprises of 15-20 % weight of total solid (Luque et al.
2010
).
4.2
DMF (2, 5-Dimethylfuran)
Until recently scientists perfectly were confident on “Bio-ethanol” as the only sat-
isfying bio-fuel in the energy market across the globe. The advent of advancement
in methods like catalytic systems for the production of 2,5 Dimethylfuran from bio-
mass opened a new window of research and hope in the world of biofuels. With its
infallible chemical characteristics fulfilling particularly all requirements as an ideal
candidate for biofuels, DMF was largely considered an auspicious bio-fuel for the
future of power generation and internal combustion engines.
