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Algae from Photobioreactors for the Production of
Biofuel

Summary:

This report discusses the use of photobioreactors for the production of biofuel
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The uses of the biodiesel and glycerol products will be covered as
well as the microbiological aspects of the production processes
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Finally, this report will contain the engineering aspects of the process which include flow
diagrams and the equipment used
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2
Introduction
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4
Microbiology and Biochemistry of Photobioreactors
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5
Cultivation and Flow of Algae in a PBR
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6
Transesterification of Biodiesel
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7
Figure 4: Block diagram-Transesterification
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8
Works Cited
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PBRs are self-cleaning and
provide a controllable environment to grow algae
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The alga
produces its own biomass and carbon dioxide using the light and the nutrients in the supplied
water
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The algal biomass that is produced from the PBR can be used
as a renewable resource for the production of biodiesel and glycerol through transesterification
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Biodiesel can also be used for
power generation and heating
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It is soluble in water and is
hygroscopic
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Microbiology and Biochemistry of Photobioreactors
Since algae require certain growing conditions, the amount of nutrients must be regulated to
provide the best growth environment
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Trace amounts of silica, calcium, magnesium, potassium, iron, manganese,
sulphur, zinc, copper, and cobalt are secondary nutrients for the growth of algae
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In addition to the listed nutrients, their growth environment
must have an average pH range between 7 and 9 to maintain the culture and prevent culture
collapse
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If the light intensity is too high, it can cause photo-inhibition due to overheating
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At higher depths, the
light intensity must be increased to provide an even growth throughout the system
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Aeration is
necessary to allow each cell to receive equal amounts of light and nutrients
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Carbon dioxide is necessary as the
algae will not photosynthesize without it
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6CO2 + 6H2O + HV ---> C6H12O6 + 6O2
Figure 1: Photosynthesis

Since plants cannot obtain all the energy required from sunlight, they use stored food as energy
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In photosynthesis, light energy is captured by the algal chloroplasts and is used to synthesize
sugars from carbon dioxide and water
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Algae also require optimal temperatures of between 20 and 24°C for growth; however, this varies
with the species used
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Algae
are quite tolerable to salinity changes but, the optimal salinity has been found to be between 20
and 24g/L, which is slightly less than the natural habitat value
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Some strains
produce more biomass under certain conditions than others
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An alga that has a high lipid
yield is good as its biomass can be further processed into biofuel
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The process begins with the introduction of
water, nutrients, CO2, and algae to the PBR from the feeding vessel
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After the growth is complete and the algae are ready for harvesting, they pass through the
separator
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Once separated, the algae slurry is pressed and
goes through a centrifuge to separate the oil and water
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The water that was separated from the oil in the centrifuge can be reintroduced into the system through the feeding vessel
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This biomass may be used as a fertiliser or can be
further processed for more biofuel products
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For example, 1,2,3-Propapetriyl trihexadecanoate
can be reacted with methanol in the presence of a potassium hydroxide catalyst to produce
biodiesel or a fatty acid methyl ester (FAME), glycerol, and water
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However, the oil must contain
triglycerides
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Therefore, not all will
contain 1,2,3-Propapetriyl trihexadecanoate, resulting in slightly different reactions and
quantities of products
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The process for transesterification can be described as follows
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Moisture left in the oil can react undesirably with the catalyst
and make soap
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The reactor can be heated to a maximum temperature of 60°C to speed the reaction
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After the reaction between the oil and the alcohol, the mixture can be separated into its
components
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The FAME that was produced must go through a washing step, drying step, and
finally, a quality control step before it can be marketed
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This can be done by moving the wash to the alcohol and glycerol
separator
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Trace water is removed, and the final glycerol product can be
tested in quality control then marketed
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Conclusion
This report has discussed the microbiology and biochemistry for the production of algal biomass
from photobioreactors, and the transesterfication process to convert algae oil to biodiesel and
glycerol
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This report has also included the
block diagrams for these processes
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(n
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What is Biodiesel
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biodiesel
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Environmental Microbiology
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M
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Gu, Environmental Microbiology
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(2010)
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In S
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Manahan, Environmental Chemistry
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Oilgae
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d
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Retrieved 05 7, 2014, from Oilgae
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oilgae
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html
Rodolfi, L
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, Bassi, N
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, Biondi, N
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, et al
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Microalgae for oil:
Strain selection, induction of lipid synthesis and outdoor mass cultivation in a low-cost
photobioreactor
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Wiley Periodicals, Inc
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(n
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Retrieved 4 1, 2014, from Goshen College:
http://www
...
edu/chemistry/biodiesel/chemistry-of/

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