Algae bioreactor
Specifically, algae bioreactors can be used to produce fuels such as biodiesel and bioethanol, to generate animal feed, or to reduce pollutants such as NOx and CO2 in flue gases of power plants.
Fundamentally, this kind of bioreactor is based on the photosynthetic reaction, which is performed by the chlorophyll-containing algae itself using dissolved carbon dioxide and sunlight.
Later, during World War II, Germany used open ponds to increase algal cultivation for use as a protein supplement.
[2] The green algae species, also known as Chlorophyta, are often used in bioreactors due to their high growth rate and ability to withstand a variety of environments.
[4] Available CO2 is also an important factor for growth and due to the lower concentration in our atmosphere, supplementary CO2 can be added as seen with the bubble column PBR below.
Microalgae also possess the ability to take up excess nitrogen and phosphorus under starvation conditions, which are essential for lipid and amino acid synthesis.
Nowadays, 3 basic types of algae photobioreactors have to be differentiated, but the determining factor is the unifying parameter – the available intensity of sunlight energy.A plate reactor simply consists of inclined or vertically arranged translucent rectangular boxes, which are often divided in two parts to affect an agitation of the reactor fluid.
The introduction of the flue gas mostly occurs at the bottom of the box to ensure that the carbon dioxide has enough time to interact with algae in the reactor fluid.
The tubes are generally made out of transparent plastics or borosilicate glass, and the constant circulation is kept up by a pump at the end of the system.
This way of introducing gas causes the problem of carbon dioxide deficiency and high concentration of oxygen at the end of the unit during the circulation, ultimately making the process inefficient.
[9] Some power companies[10] already established research facilities with algae photobioreactors to find out how efficient they could be in reducing CO2 emissions, which are contained in flue gas, and how much biomass will be produced.
[12] The utilization of algae as food is very common in East Asian regions[13] and is making an appearance around the world for uses in feedstock and even pharmaceuticals due to their high value products.
[14] The algae, especially some species which contain over 50 percent oil and a lot of carbohydrates, can be used for producing biodiesel and bioethanol by extracting and refining the fractions.
