dc.description.abstract |
Continued use of fossil fuels is now widely recognized as unsustainable because of di
minishing supplies and the contribution of these fuels to the increased carbon dioxide
concentration in the environment. Microalgae are considered as a most capable feedstock
for the generation of biofuels due to its several advantages, compared to the feedstock
of first- (food feedstock) and second- (non-food feedstock) generation biofuels. It is a
photosynthetic organisms that convert carbon dioxide to potential biofuels, foods, feeds
and high-values bioactives. When comparing microalgae as feedstock for biofuel pro
duction with conventional raw materials, several advantages are observed: much faster
growth rate (doubling time of hours), greenhouse gas fixation ability (net zero emission
balance), higher area yields (potentially 15- 300 times more), possibility of growing in non
arable land, no competition with food crops, less land requirement, cheaper raw materials,
lower water consumption, possibility to grow in saline water and non-potable water, etc.
However, one major challenge of microalgal biofuels lies in algal biomass harvesting and
nutritional cost for production. Therefore, work described in thesis was designed, devel
opment an integrated process of microalgal production using anaerobic digestion under
outdoor conditions. This decreases the production cost of microalgae as well as biofuel.
The main objective of this thesis was to develop a closed loop for biological wastewater
treatment system of AD slurry that could be utilized for algal growth and simultaneously
produce the renewable energy in the form of biomethane and remove polluting nutrients as
well as reduce the greenhouse gases. The integration of microalgae growth with anaerobic
digestion could significantly improve the economics and energy balance of biofuels produc
tion. Nutrient removal, in particular nitrogen and phosphorus; and COD reduction from
wastewater is a developing regulatory need and the use of algae cultivation could create
a unique integration between waste treatment and biofuel production. Both the quanti
tative and qualitative aspect of the mass (substrate and biomass) and biogas production
was studied and modelled. This integrated process of Chlorella pyrenoidosa cultivation coupled with anaerobic digestion (under outdoor conditions) in order to properly design a microalgae growth-anaerobic digestion process to minimize the overall biofuel production
costs. The process also reduces the need for fresh water by reusing AD slurry water. |
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