Current state of research and development in the area of cultivation of microalgal biomass
In the document “Alternative type of fuel for commercial aviation”, Boing experts point out that sea algae are the most optimal raw material for biofuel production among alternative fuel sources, which could reduce the worldwide pressure of petroleum fuel.
At present, practically all leading world corporations are developing various systems and photobioreactors for microalgae cultivation. These corporations range from world energy giants such as Chevron and Shell as well as fuel consumers Boing, Chysler NextDiesel, etc. to De Beers and Nestle, which do not specialize in energy production, as well as large private investors (Bill Gates, Sapphire Energy, etc).
For this problem solution, it is necessary to develop apparatuses or systems that at minimum energy consumption provide the following:
1 high mass exchange of ŃÎ2
2 efficient and uniform illumination of the whole suspension volume
3 minimal overgrowth of light-transmitting surfaces
4 minimal foaming
5 minimal traumatization of microalgae at stirring
6 the possibility of cultivation of various forms of photosynthesizing microorganisms including envelope-free ones
The work conducted in the world is aimed at reducing the cost of the produced algae biomass by using open natural and artificial water bodies, reservoirs of sewage treatment plants, by using associated gases of power plants as well as by developing different open and closed systems for microalgae cultivation.
The most promising solution for producing large amounts of microalgal biomass with desired properties (high fat content, etc.) is to cultivate them in specially designed closed systems - photobioreactors, which create optimal conditions i.e. the required temperature, illumination, gas exchange and nutrients supply.
The developments of Valcent Products Inc., USA (Vertigro technology) are the best known in this area. The Vertigro system consists of vertical bioreactors made of thin film materials that allow sunlight to penetrate.
Photobioreactors of GreenFuel Technologies Corporation and Arizona Public Service Company present a series of angled or vertical transparent tubes with a diameter of 10-20 cm for cultivation of algae. The bioreactor is 2.5 m or more high. Bioreactors are sun-oriented. Exhaust gases of the power plant are pumped into the bioreactor creating the circulation of water and algae in the reactor. “Mature” algae precipitate to the bottom of the reactor. CO2 consumption occurs during daylight hours.
Photobioreactors of BioKing and AEN Engineering GmbH&Co present a system of transparent horizontal plastic tubes in which culture fluid containing microalgae forcibly circulates. Carbon dioxide and various additives required for the culture growth are supplied to this fluid, and oxygen emitted during the microalgae lifecycle is removed.