Biological Hydrogen Production As Fuel
Biological hydrogen production is mainly done in bioreactors and is based on hydrogen production by some algae. In fact, the algae produce hydrogen under certain conditions: in the late nineties it was discovered that depriving the algae of sulfur they stop producing oxygen, ie normal photosynthesis, and began to produce hydrogen. The term biohydrogen indicates the molecular hydrogen produced by organic farming.
The biological processes that lead to the production of hydrogen may provide for the gasification of biomass or the use of metabolic processes of microorganisms (bacteria, cyanobacteria as well as microalgae) can produce hydrogen using energy as a source of heat and half organic ( thermophilic bacteria), the light and half organic (photosynthetic bacteria) or light and water (algae).Hydrogen production processes that do not involve the use of living organisms can be electrolysis, the oxidation of metal compounds or the reversible steam reforming (coal gasification): the latter is actually the method of hydrogen production far the most used.
One of the advantages of organic production of hydrogen is to use an existing process in nature to convert a primary energy source in the hydrogen carrier by lowering the rate of pollutant waste of this process. For example, any carbon dioxide emissions in different biological processes that use hydrogen to produce organic means do not go to increase the impact of global warming, because it does not come from fossil fuels. This advantage, of course, does not apply in the case of steam reforming using as initial source of coal. However, for electrolysis using solar energy (photovoltaic panels), wind or other renewable sources for electricity generation are equally clean and sustainable from an environmental point of view.
Problems in the Implementation of Bioreactors
Decreased production of hydrogen via photosynthetic activity due to the formation of a proton gradient
Competitive type of inhibition of photosynthetic production of hydrogen from the carbon dioxide
The need for a bond in photosystem II bicarbonate (PSII) to maintain efficient photosynthetic activity
Competitive capture of electrons by oxygen during the production of hydrogen from algae
Economic feasibility of energy-efficiency: the conversion of sunlight into hydrogen must reach 7-10% (algae in their natural form can reach more than 0.1%)
Currently there are projects underway to address these problems through the use of bioengineering.
2006 - Researchers at the University of Bielefeld and the University of Queennsland, have genetically modified unicellular green alga Chlamydomonas reinhardtii in order to make possible the production of seaweed by large amounts of hydrogen.  Stm6, as been named, can produce long-term, five times the volume of hydrogen produced dall'alga in their natural state, with an energy efficiency of production of around a 0.6 to 2%.
2006 - An unpublished article, University of California at Berkeley (the program was conducted by Midwest Research Institute, an external operator who works for the NREL) may have found the technological solution that allows a higher level of energy efficiency 10%, making feasible an economic point of view the project. This was achieved by shortening the blocks of chlorophyll in photosynthesis organelles Members, the Tasios Melis has "probably" over the threshold.
A 2007 study conducted by researchers at Penn State University has shown the ability to produce hydrogen with high efficiency using a microbial electrolysis cell with acetic acid. The latter is the predominant acid produced in the fermentation of glucose and cellulose. The cell produces energy stored in hydrogen with an efficiency of 288%. Subtracted from that required for its operation, however, the cell provides 144% more energy input.
A culture of algae on the size of the state of Texas would have the amount of hydrogen needed to meet the demand from around the world. For example 25,000 km ² would be enough to supplant the use of gasoline in the United States of America.
In 1939 a German researcher, Hans Gaffron, while studying at the University of Chicago, noted that the algae he was observing the Chlamydomonas reinhardtii (green alga), sometimes passing from the production of oxygen to hydrogen. Gaffron was not able to discover the causes of this change, and for many years the cause was unknown. In the late nineties Professor Anastasios Melis, then a researcher at the University of California at Berkeley, found that if the algal culture was deprived of sulfur it ceases to produce oxygen (normal photosynthesis), going to produce hydrogen. He discovered that the enzyme responsible for this reaction is hydrogenase, but that the hydrogenase lost its function in the presence of oxygen. Melis found that depriving the algae of sulfur it interrupted the internal flow of oxygen, thus creating an environment where the hydrogenase could react, producing hydrogen. The Chlamydomonas moeweesi is considered by scholars to a good candidate for the production of hydrogen.
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