In the last few years the number of people who want to use bio-diesel has grown exponentially. As has the ways bio-diesel can be used in everything from cleaning up oil spills and generating electricity to cleaning and cooking. However the largest use is still fuel for automobiles. With the increased demand there has arisen one major problem, that is keeping bio-diesel from becoming a wide spread alternative to traditional fuels. That problem as with most new technology is production there simply is not enough. Bio-mass is needed to produce the bio-diesel, but it is very hard to come by. There is a solution to this problem though. Many major producers of bio-diesel are switching from traditional crops and bio-waste to a more sustainable crop of algae.
Yield of Various Plant Oils
Crop Oil in Liters per hectare
Castor 1413
Sunflower 952
Safflower 779
Palm 5950
Soy 446
Coconut 2689
Algae 100000
Today's experiment is a simple indoor bio-reactor. Algae can be grown in a photo bio-reactor (PBR). A PBR is a bio-reactor which incorporates some type of light source. Virtually any translucent container could be called a PBR; however the term is more commonly used to define a closed system, as opposed to an open tank or pond. It allows more species to be grown, it allows the species that are being grown to stay dominant, and it extends the growing season, only slightly if unheated and if heated it can produce year round. Because PBR systems are closed, all essential nutrients must be introduced into the system to allow algae to grow and be cultivated. A PBR can be operated in "batch mode", but it is also possible to introduce a continuous stream of sterilized water containing nutrients, air, and carbon dioxide. Algal culture systems can be illuminated by artificial light, Solar light or by both. Naturally illuminated Algal Culture systems with large illumination surface areas include flat-plate, horizontal/serpentine tubular airlift, and inclined tubular. Generally, laboratory-scale photo bio-reactors are artificially illuminated (either internally or externally) using fluorescent lamps or other light distributors.
Flow description:
1. From the feeding vessel, the flow progresses to the diaphragm pump which moderates the flow of the algae into the actual tube. Built into the pump is the CO2 inlet valve.
2. The photo bio-reactor itself is used to promote biological growth by controlling environmental parameters including light. The tubes are acrylic and are designed to have light and dark intervals to enhance the growth rate.
3. The photo bio-reactor has a built-in cleaning system that will be internally clean the tubes without stopping the production.
4. After the algae have completed the flow through the photo bio-reactor, it passes back to the feeding vessel. As it progresses through the hoses, the oxygen sensors determine how much oxygen has built up in the plant and it is released in the feeding vessel itself. It is also at this stage that the optical Cell Density sensor determines the harvesting rate.
5. When the algae are ready for harvesting, the algae passes through the connected filtering system. This filter collects the algae that are ready for processing, where the remaining algae passes back to the feeding vessel.
6. And the flow continues.
Advantages of using a photo bio-reactor:
High photo bio-reactor Biomass Productivity and cell density
Less contamination, water use, & CO2 losses
Better light utilization & mixing
Controlled culture conditions
Disadvantages of using a photo bio-reactor:
High capital cost associated with construction costs, circulation pumps, and nutrient-loading systems
Absence of evaporate cooling, which can lead to very high temperatures
Accumulation of high concentration of photo-synthetically generated O2 leading to photo oxidation damage
Bio-fouling of interior surfaces and difficulty of cleaning them
Cell damage by shear stress
Deterioration of materials
Requirements to develop a high-performance photo bio-reactor for algal cultivation:
In order to attain high productivity, the volume of the non-illuminated parts of the reactor should be minimized.
In order to ensure a high efficiency of light use by the culture, the design must provide for the uniform illumination of the culture surface and the fast mass transfer of CO2 and O2.
To prevent rapid fouling of light-transmitting surfaces of reactors, photo bio-reactors must be frequently shut down for their mechanical cleaning and sterilization
High rates of mass transfer must be attained by means that neither damage cultured cells nor suppress their growth.
For the industrial-scale production of biomass, the energy consumption required for mass transfer and the arrangement of the light-receiving surface of the algal suspension must be reduced to its minimum possible.
I have developed a bio-reactor using a fish tank I will upload photos as soon as I start/finish construction and make sure that it produces as expected. It is a simple setup I will have a heater in the water to keep it warm, aerators in the bottom to deliver the required Co2, and finally an automatic timed liquid dispenser to deliver Algae Food Concentrate. If you use this remember a little goes a long way. I am planning on using a fresh water algae called Scenedesmus dimorphus. Scenedesmus dimorphus is a unicellular algae in the class Chlorophyceae. While this is one of the preferred species for oil yield for bio-diesel, one of the problems with Scenedesmus is that it's heavy, and forms thick sediments if not kept in constant agitation.
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