Oilgae for Algaculture

1
Why algae? In the beginning, there were algae,
but there was no oil. Then, from algae came
oil. Now, the algae are still there, but oil is
fast depleting. In future, there will be no oil,
but there will still be algae. So, doesnt it
make sense to explore if we can again get oil
from algae?
-Oilgae.com Algae is more
efficient than other biofuels such s soy or corn
oil in terms of nutrients and land. It has the
potential to become the fuel of choice for the
future, but for this to happen, an economically
efficient reactor must be designed.
Thermal Experimentation Temperature mitigation
is a vital constraint for any reactor design.
Most algae are very sensitive to temperature
fluctuations, so keeping the reactor warm when it
is cold outside and cool when it is hot is very
important. This task can also be very
difficult. In hot weather, most of the reactors
heat comes from energy absorbed from the sun
rather than from ambient air temperature. The bag
reactor design uses the earth as a heat sink in
hot weather, dissipating some of the energy taken
in by the sun. The algae team ran several tests
to observe temperature change in each of the
reactors.
Oilgae for Algaculture
Sponsored by
Designing an economically efficient reactor
capable of growing algae for use in biofuel
production
School of Chemical, Biological, and Environmental
Engineering Oilgae Team Joshua Bruce, Sarah
Herzog, Michael Robinson
Plate Reactor
Bag Reactor
The graphs to the left show the temperature
change of the two reactors with respect to time
of day, ambient temperature, light, and total
light energy received by the reactors. The
results were as expected The bag reactor heated
up more quickly but had a lower peak temperature.
It cooled more quickly, but stayed warmer at
night. These results show that the bag reactor
design helps to mitigate temperature
fluctuations.

• Features
• 3 x 1 x 1 clear vinyl bag set into the ground
• Air bubbled through pipe attached to floor of bag
  and released through a valve on the far side
• Agitation system consisting of a mechanical arm
  which periodically pushes down on one end of the
  bag, creating a wave motion.

• Design objectives
• Low capital and operating cost
• High conversion of nutrients to lipids
• High reproduction rate
• Temperature fluctuations mediated
• Durable
• Ease of operation
• Limited additional infrastructure needed

• Benefits
• Bag material very inexpensive
• Ground provides temperature mediation
• Air source need not be high pressure as agitation
  does not depend on pressure.

• Features
• 1 x 2 x 1/2 clear acrylic box, with a center
  plate dividing the box in two.
• One end of the box is hinged and can be opened
  for periodic cleaning.
• Air is bubble in one side at a high flowrate to
  cause the media to flow. A smaller flow of air is
  bubble in the opposite direction to keep the
  algae from sticking to the top side of the
  reactor.

Biofuel Processing Once the algae is grown, it
needs to be processed in order to harvest the
oil. Currently it is only feasible to harvest oil
from algae with very high lipid content.
Researchers at OSU are investigating
possibilities of harvesting ethanol from the
algaes cell walls. This would make processing
lower lipid content algae economically feasible,
and make growing algae in open reactors possible
since species contamination would no longer be as
much of an issue.
Results The bag reactor succeeded in mitigating
temperature fluctuations, as shown in the graphs
to the right. However, leaks were frequent and
difficult to repair. A more sturdy material
should be investigated in future testing.
What algae need to grow Light Light is
essential for algae. Access to light limits the
size and shape of the reactor. Algae absorb
different wavelengths of light depending on their
color. Carbon Algae use carbon, usually in the
form of CO2 gas, to grow and make oil. The amount
of CO2 available to the algae is therefore a
design constraint for algae reactors. Other
nutrients Algae also need other nutrients to
survive and flourish, such as elements in
seawater or silica. Temperature Algae are
usually sensitive to temperature and cannot get
too hot or too cold. This is an important issue
for bioreactors that will be located outside.

• Benefits
• Based on well understood triangle reactor
• No additional agitation system needed
• Easy maintenance

Results When compared to the triangle air lift
reactor, the plate reactor has a much lower cost,
takes up less space, and has a lower pressure
head. Temperature mitigation strategies should be
investigated in the future, in addition to more
suitable materials of construction.
Acknowledgements The oilgae team would like to
acknowledge Dr. Yokochi, Dr. Harding, and Dr.
Murthy for their generous contributions to this
project. Without their help, neither of these
reactors would have been built. We would also
like to thank several supportive community
members who helped us find a location for our
reactors.