||This article may be too technical for most readers to understand. (September 2010)|
Biohydrogen reactors use a method of photobiological water splitting which is done in a closed photobioreactor based on the production of hydrogen by algae. Algae produce hydrogen under certain conditions. In 2000 it was discovered that if C. reinhardtii algae are deprived of sulfur they will switch from the production of oxygen, as in normal photosynthesis, to the production of hydrogen.
In 1939 a German researcher named Hans Gaffron, while working at the University of Chicago, observed that the algae he was studying, Chlamydomonas reinhardtii (a green-algae), would sometimes switch from the production of oxygen to the production of hydrogen. He 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 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 responsible for this reaction is hydrogenase, 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.
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 have genetically changed the single-cell green alga Chlamydomonas reinhardtii 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 - Anastasios Melis 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.
2011 - A team at Argonne's Photosynthesis Group demonstrated how platinum nanoparticles can be linked to key proteins in algae to produce hydrogen fuel five times more efficiently.
As of 2009, HydroMicPro is testing plate reactors.
As of 2013, Grow Energy has developed novel system for the large-scale production of hydrogen from structural bioreactors.
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.
In 2004, the US Department of Energy issued a selling price of $2.60 per kilogram ($1.18/lb) 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 2004 achieved-efficiency is only 1% and the 2004 actual selling price is estimated at $13.53 per kilogram ($6.14/lb)
According to a 2004 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 cell concentration, a truncated antennae mutant and 10 cm pond depth.
The chlorophyll (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 II (PSII) for efficient photosynthetic activity.
- 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.
- Analytical approaches to photobiological hydrogen production in unicellular green algae.
- Wired-Mutant Algae Is Hydrogen Factory
- Algae: Power Plant of the Future?
- Reengineering Algae To Fuel The Hydrogen Economy
- Algae Could One Day be Major Hydrogen Fuel Source Newswise, Retrieved on June 30, 2008.
- Melis A and Happe T (2001). "Hydrogen Production: Green Algae as a Source of Energy". Plant Physiol. 127 (3): 740–748. doi:10.1104/pp.010498. PMC 1540156. PMID 11706159.
- Department of Energy report winter 2000
- 2005-The anaerobic life of the photosynthetic alga
- Hydrogen from algae - fuel of the future?
- Chl antenna
- DOE 2007 Report 15 %
- DOE 2008 Report 25 %
- Algae turned into high-temperature hydrogen source
- Self-organized photosynthetic nanoparticle for cell-free hydrogen production
- Teaching algae to make fuel
- Photosynthetic electron partitioning between [FeFe]-hydrogenase and ferredoxin:NADP+-oxidoreductase (FNR) enzymes in vitro
- Algae creates hydrogen fuel
- Hydrogen from microalgae
- Hydral Energy Systems
- Growing hydrogen for the cars of tomorrow
- 2004-Updated Cost Analysis of Photobiological Hydrogen
- 2004- Updated cost analysis of photobiological hydrogen production from chlamydomonas reinhardtii green algae
- Photobiological hydrogen production—prospects and challenges
- 2005-A prospectus for biological H2 production
- 2004-Maximizing photosynthetic efficiencies and hydrogen production in microalgal cultures