(62f) Modeling and Optimization of Algae Based Biodiesel Production

Processing
of biodiesel from algae biomass has attracted much interest in recent times due
to many reasons. Significant amongst them are global warming and scarcity in
fossil fuels. It has been suggested that this third generation biofuel, a
carbon neutral alternative, is capable of meeting the existing demand for
transport fuels [1]. However, substantial challenges are encountered in
deriving fuels from algae biomass. Primary amongst them is the relatively
higher cost of cultivating and harvesting algae species. Due to this reason,
currently, algae based biofuels cost much higher than the biofuels from first
generation and second generation biofuel feedstock [2].

This
work focuses on modeling and optimization of algae based biodiesel production. Design
parameters, for cultivation of algal species, at a geographical location are
affected by that location's climatic conditions such as annual solar irradiance.
Hence, geographical location, at which algae is cultivated, plays a vital role
in the biodiesel production. Another significant factor to be considered for producing
maximum amount of biodiesel is the selection of algal species. There are a
variety of algal species present throughout the world, however, not all algal
species are suitable for biodiesel production because of varying amounts of oil
content and specific growth rates. Hence, selection of algal species is also an
important factor in determining the cost of biodiesel production. There are a
number of technologies for each process involved in the production of biodiesel
from algae biomass but the question of which technology, for which species, and
at which location, to attain maximum profits is still an open challenge to the
researchers. Figure 1 presents the tasks that should be completed to produce
algae-based biodiesel and options/technologies (which can be used to achieve
these tasks) considered in this work. Using Figure 1, a disjunctive programming
model is developed to determine the algal species, the location for the cultivation
of algae, and the optimum route from growth of algae to production of biodiesel
by selecting one technology for each process with the objective of minimum cost
of biodiesel production. The resulting Mixed Integer Nonlinear Programming
(MINLP) model is solved using GAMS 23.6.5/SBB solver. With the model parameters
used, 8000 tons/year of biodiesel can be produced at a cost of about $153 per
gallon for a period of ten years using the selected technologies. Accordingly,
Tricornutum species was selected to grow at all the given locations by means of
artificial growing technique-tubular photobioreactor. The cultivated algae were
harvested through flocculation which was then concentrated using centrifugation.
The algae biomass was dried by low pressure shelf drying followed by extraction
of algal oil by expeller press and finally, the algal oil was sent to
transesterification for biodiesel production.

REFERENCES

1.       Y. Chisti, Biodiesel from microalgae, Biotechnol. Adv. 25 (2007), pp. 294?306. 

2.      
Sheehan, J., Dunahay, T., Benemann, J., Roessler, P. A Look Back
at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from
Algae; Close-Out Report. U.S. Department of Energy (1998).