Algae bioreactor

An algae bioreactor is used for cultivating micro or macro algae. Algae may be cultivated for the purposes of biomass production (as in a seaweed cultivator), wastewater treatment, CO₂ fixation, or aquarium/pond filtration in the form of an algae scrubber. Algae bioreactors vary widely in design, falling broadly into two categories: open reactors and enclosed reactors. Open reactors are exposed to the atmosphere while enclosed reactors, also commonly called photobioreactors, are isolated to varying extent from the atmosphere. Specifically, algae bioreactors can be used to produce fuels such as biodiesel and bioethanol, to generate animal feed, or to reduce pollutants such as NO_x 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 energy. The carbon dioxide is dispersed into the reactor fluid to make it accessible for the algae. The bioreactor has to be made out of transparent material.

The algae are photoautotroph organisms which perform oxygenic photosynthesis.

The equation for photosynthesis:

Some of the first experiments with the aim of cultivating algae were conducted in 1957 by the "Carnegie Institution" in Washington. In these experiments, monocellular Chlorella were cultivated by adding CO₂ and some minerals. In the early days, bioreactors were used which were made of glass and later changed to a kind of plastic bag. The goal of all this research has been the cultivation of algae to produce a cheap animal feed.

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 vertically arranged or inclined rectangular boxes which are often divided in two parts to effect an agitation of the reactor fluid. Generally these boxes are arranged to a system by linking them. Those connections are also used for making the process of filling/emptying, introduction of gas and transport of nutritive substances, easier. 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.

...
Wikipedia