Algae bioreactor
Encyclopedia
An algae bioreactor or photobioreactor
is used for cultivating algae
on purpose to fix CO2 or produce biomass
. 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 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 oxygenetic photosynthesis.
The equation for photosynthesis:
" in Washington. In these experiments, the 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.
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.
consists of vertical arranged cylindrical column, made out of transparent material. The introduction of gas takes place at the bottom of the column and causes a turbulent stream to enable an optimum gas exchange. At present these types of reactors are built with a maximum diameter of 20 cm to 30 cm in order to ensure the required supply of sunlight energy. This type allows for a reduction of the harmful shared forces.
The biggest problem with the sunlight determined construction is the limited size of the diameter. Feuermann et al. invented a method to collect sunlight with a cone shaped collector and transfer it with some fiberglass cables which are adapted to the reactor in order to enable constructions of a column reactor with wider diameters. - on this scale the energy consumption due to pumps etc. and the CO2 cost of manufacture may outweigh the CO2 captured by the reactor.
Some power companies 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. Algae biomass has many uses and can be sold to generate additional income. The saved emission volume can bring an income too, by selling emission credits to other power companies.
The utilisation of algae as food is very common in East Asian regions . Most of the species contain only a fraction of usable proteins and carbohydrates, and a lot of minerals and trace elements. Generally, the consumption of algae should be minimal because of the high iodine content. For example, if someone has hyperthyroidism it could be very dangerous for their health. Likewise, many species of diatomaceous algae produce compounds unsafe for humans.
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. This point is very interesting, because the algae biomass is generated 30 times faster than some agricultural biomass , which is commonly used for producing biodiesel.
Photobioreactor
thumb|upright|[[Moss bioreactor|Moss photobioreactor]] with [[Physcomitrella patens]]A photobioreactor is a bioreactor that incorporates some type of light source to provide photonic energy input into the reactor...
is used for cultivating algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
on purpose to fix CO2 or produce biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
. 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
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
-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 oxygenetic photosynthesis.
The equation for photosynthesis:
Historical background
The first experiments with the aim of cultivating algae were conducted in 1957 by the "Carnegie InstitutionCarnegie Institution for Science
The Carnegie Institution for Science is an organization in the United States established to support scientific research....
" in Washington. In these experiments, the 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.
Frequently used photo reactor types
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.Plate photobioreactor
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 gasFlue gas
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced at power plants...
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.
Tubular photobioreactor
A tubular reactor consists of vertical or horizontal arranged tubes, connected together to a pipe system. The algae-suspended fluid is able to circulate in this tubing. 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. The introduction of gas takes place at the end/beginning of the tube system. This way of introducing gas causes the problem of deficiency of carbon dioxide, high concentration of oxygen at the end of the unit during the circulation, and bad efficiency.Bubble column photobioreactor
A bubble column photo reactorBubble column reactor
A bubble column reactor is an apparatus used for gas-liquid reactions first applied by Helmut Gerstenberg. It consists of vertical arranged cylindrical columns. The introduction of gas takes place at the bottom of the column and causes a turbulent stream to enable an optimum gas exchange. It is...
consists of vertical arranged cylindrical column, made out of transparent material. The introduction of gas takes place at the bottom of the column and causes a turbulent stream to enable an optimum gas exchange. At present these types of reactors are built with a maximum diameter of 20 cm to 30 cm in order to ensure the required supply of sunlight energy. This type allows for a reduction of the harmful shared forces.
The biggest problem with the sunlight determined construction is the limited size of the diameter. Feuermann et al. invented a method to collect sunlight with a cone shaped collector and transfer it with some fiberglass cables which are adapted to the reactor in order to enable constructions of a column reactor with wider diameters. - on this scale the energy consumption due to pumps etc. and the CO2 cost of manufacture may outweigh the CO2 captured by the reactor.
Industrial usage
The cultivation of algae in a photobioreactor creates a narrow range of industrial application possibilities.Some power companies 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
Flue gas
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced at power plants...
, and how much biomass will be produced. Algae biomass has many uses and can be sold to generate additional income. The saved emission volume can bring an income too, by selling emission credits to other power companies.
The utilisation of algae as food is very common in East Asian regions . Most of the species contain only a fraction of usable proteins and carbohydrates, and a lot of minerals and trace elements. Generally, the consumption of algae should be minimal because of the high iodine content. For example, if someone has hyperthyroidism it could be very dangerous for their health. Likewise, many species of diatomaceous algae produce compounds unsafe for humans.
The algae, especially some species which contain over 50 percent oil and a lot of carbohydrates, can be used for producing biodiesel
Biodiesel
Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel consisting of long-chain alkyl esters. Biodiesel is typically made by chemically reacting lipids with an alcohol....
and bioethanol by extracting and refining the fractions. This point is very interesting, because the algae biomass is generated 30 times faster than some agricultural biomass , which is commonly used for producing biodiesel.