Biological hydrogen production
Encyclopedia
Closed system
-In physics:In thermodynamics, a closed system can exchange energy , but not matter, with its surroundings.In contrast, an isolated system cannot exchange any of heat, work, or matter with the surroundings, while an open system can exchange all of heat, work and matter.For a simple system, with...
photobioreactor based on the production of hydrogen
Hydrogen production
Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...
by 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...
. 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...
produce hydrogen under certain conditions. In 2000 it was discovered that if C. reinhardtii
Chlamydomonas reinhardtii
Chlamydomonas reinhardtii is a single celled green alga about 10 micrometres in diameter that swims with two flagella. They have a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light.Although widely distributed...
algae are deprived of sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
they will switch from the production of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, as in normal photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
, to the production of hydrogen.
History
In 1939 a German researcher named Hans GaffronHans Gaffron
Dr. Hans Gaffron is born in Lima, Peru, on May 17, 1902, as the son of the German physician Eduard Gaffron and his wife Hedwig von Gevekot....
, while working at the University of Chicago, observed that the algae he was studying, Chlamydomonas reinhardtii
Chlamydomonas reinhardtii
Chlamydomonas reinhardtii is a single celled green alga about 10 micrometres in diameter that swims with two flagella. They have a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light.Although widely distributed...
(a green-algae), would sometimes switch from the production of oxygen to the production of hydrogen. Gaffron never discovered the cause for this change and for many years other scientists failed in their attempts at its discovery. In the late 1990s professor Anastasios Melis
Anastasios Melis
Anastasios Melis is a biologist at the University of California, Berkeley who is researching the possibility of creating hydrogen from algae. Hydrogen power is considered one of the key ways of producing electricity without continuing to use up fossil fuels...
a researcher at the University of California at Berkeley discovered that if the algae culture medium is deprived of sulfur it will switch from the production of oxygen (normal photosynthesis), to the production of hydrogen. He found that the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
responsible for this reaction is hydrogenase
Hydrogenase
A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen . Hydrogenases play a vital role in anaerobic metabolism....
, but that the hydrogenase lost this function in the presence of oxygen. Melis found that depleting the amount of sulfur available to the algae interrupted its internal oxygen flow, allowing the hydrogenase an environment in which it can react, causing the algae to produce hydrogen. Chlamydomonas moewusii is also a good strain for the production of hydrogen. Scientists at the U.S. Department of Energy’s Argonne National Laboratory are currently trying to find a way to take the part of the hydrogenase enzyme that creates the hydrogen gas and introduce it into the photosynthesis process. The result would be a large amount of hydrogen gas, possibly on par with the amount of oxygen created.
Milestones
1997 Professor Anastasios Melis discovered, after following Hans Gaffron's work, that the deprivation of sulfur will cause the algae to switch from producing oxygen to producing hydrogen. The enzyme, hydrogenase, he found was responsible for the reaction.
2006 - Researchers from the University of Bielefeld and the University of Queensland
University of Queensland
The University of Queensland, also known as UQ, is a public university located in state of Queensland, Australia. Founded in 1909, it is the oldest and largest university in Queensland and the fifth oldest in the nation...
have genetically changed the single-cell green alga Chlamydomonas reinhardtii
Chlamydomonas reinhardtii
Chlamydomonas reinhardtii is a single celled green alga about 10 micrometres in diameter that swims with two flagella. They have a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light.Although widely distributed...
in such a way that it produces an especially large amount of hydrogen. The Stm6 can, in the long run, produce five times the volume made by the wild form of alga and up to 1.6-2.0 percent energy efficiency.
2007 - It was discovered that if copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
is added to block oxygen generation algae will switch from the production of oxygen to hydrogen
2007 - Anastasios Melis
Anastasios Melis
Anastasios Melis is a biologist at the University of California, Berkeley who is researching the possibility of creating hydrogen from algae. Hydrogen power is considered one of the key ways of producing electricity without continuing to use up fossil fuels...
studying solar-to-chemical energy conversion efficiency in tlaX mutants of Chlamydomonas reinhardtii, achieved 15 % efficiency, demonstrating that truncated Chl antenna size would minimize wasteful dissipation of sunlight by individual cells This solar-to-chemical energy conversion process could be coupled to the production of a variety of bio-fuels including hydrogen.
2008 - Anastasios Melis
Anastasios Melis
Anastasios Melis is a biologist at the University of California, Berkeley who is researching the possibility of creating hydrogen from algae. Hydrogen power is considered one of the key ways of producing electricity without continuing to use up fossil fuels...
studying solar-to-chemical energy conversion efficiency in tlaR mutants of Chlamydomonas reinhardtii, achieved 25 % efficiency out of a theoretical maximum of 30%.
Economics
It would take about 25,000 square kilometres to be sufficient to displace gasoline use in the US. To put this in perspective, this area represents approximately 10% of the area devoted to growing soya in the US.The US Department of Energy has targeted a selling price of $2.60 / kg as a goal for making renewable hydrogen economically viable. 1 kg is approximately the energy equivalent to a gallon of gasoline. To achieve this, the efficiency of light-to-hydrogen conversion must reach 10% while current efficiency is only 1% and selling price is estimated at $13.53 / kg.
According to the DOE cost estimate, for a refueling station to supply 100 cars per day, it would need 300 kg. With current technology, a 300 kg per day stand-alone system will require 110,000 m2 of pond area, 0.2 g/l
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
cell concentration, a truncated antennae mutant and 10 cm pond depth. All those estimates however are obsolete in light of the previously mentioned improvements in efficiency, and the citations for the above estimates are dated 2004.
Areas of research to increase efficiency include developing oxygen-tolerant FeFe-hydrogenase
Hydrogenase
A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen . Hydrogenases play a vital role in anaerobic metabolism....
s and increased hydrogen production rates through improved electron transfer.
Truncated antenna
The chlorophyllChlorophyll
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...
(Chl) antenna size in green algae is minimized, or truncated, to maximize photobiological solar conversion efficiency and H2 production. The truncated Chl antenna size minimizes absorption and wasteful dissipation of sunlight by individual cells, resulting in better light utilization efficiency and greater photosynthetic productivity by the green alga mass culture.
Bioreactor design issues
- Restriction of photosynthetic hydrogen production by accumulation of a proton gradient.
- Competitive inhibition of photosynthetic hydrogen production by carbon dioxide.
- Requirement for bicarbonate binding at photosystem IIPhotosystem IIPhotosystem II is the first protein complex in the Light-dependent reactions. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. The enzyme uses photons of light to energize electrons that are then transferred through a variety of coenzymes and cofactors to reduce...
(PSII) for efficient photosynthetic activityPhotosynthetic efficiencyThe photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in plants and algae. Photosynthesis can be described by the simplified chemical reactionwhere CH2O represents carbohydrates such as sugars, cellulose, and lignin.The value of the...
. - Competitive drainage of electrons by oxygen in algal hydrogen production.
- Economics must reach competitive price to other sources of energy and the economics are dependent on several parameters.
- A major technical obstacle is the efficiency in converting solar energy into chemical energy stored in molecular hydrogen.
Attempts are in progress to solve these problems via bioengineering.
See also
- AlgaeAlgaeAlgae 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...
- AlgacultureAlgacultureAlgaculture is a form of aquaculture involving the farming of species of algae.The majority of algae that are intentionally cultivated fall into the category of microalgae...
- BiohydrogenBiohydrogenBiohydrogen is defined as hydrogen produced biologically, most commonly by algae and bacteria. Biohydrogen is a potential biofuel obtainable from both cultivation and waste organic materials.-Introduction:...
- Hydrogen productionHydrogen productionHydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...
- PhotohydrogenPhotohydrogenPhotohydrogen is hydrogen produced with the help of artificial or natural light This is how the leaf of a tree splits water molecules into protons , electrons and oxygen...
- Timeline of hydrogen technologiesTimeline of hydrogen technologiesTimeline of hydrogen technologies — A timeline of the history of hydrogen technology.-1600s:* 1625 - First description of hydrogen by Johann Baptista van Helmont...