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Biorock, also known as Seacrete or Seament, is a trademark name used by Biorock, Inc. to refer to the substance formed by electro-accumulation of minerals dissolved in seawater. Prof. Wolf Hilbertz developed the process and patented it in 1979. The building process, popularly called accretion, is not to be confused with Biorock sewage treatment. The biorock building process grows cement-like engineering structures and marine ecosystems, often for mariculture of corals, oysters, clams, lobsters and fish in salt water. It works by passing a small electric current through electrodes in the water. The structure grows more or less without limit as long as current flows. == History == In an attempt to slow the damage done to the world’s coral, artificial reefs have been built since the 1950s out of materials ranging from concrete blocks to discarded tires. However, most of these plans have failed to provide a new coral habitat. Most notoriously, the attempt using tires off the shore of Fort Lauderdale has become an environmental disaster.〔Skoloff, Brian (2007) (Tire reef off Florida proves a disaster ) USA Today 2/17/2007〕 There have been some successes with artificial reefs, but most remain relatively barren compared with natural reefs. The one notable exception is the work of architect/marine scientist Prof. Wolf Hilbertz (born 1938, died 2007) and marine biologist Dr. Thomas J. Goreau (born 1950). Biorock technology arose from experiments in the 1970s when Hilbertz was studying how seashells and reefs grow, by passing electric currents through salt water. In 1974, he found that as the salt water electrolyzes, calcium carbonate (aragonite) combines with magnesium, chloride and hydroxyl ions to slowly form around the cathode, eventually coating the electrode with a material similar in composition to complex magnesium oxychloride cements and as strong as concrete. Over time cathodic protection replaces the negative chloride (Cl-)ion with dissolved bicarbonate (HCO3-) to harden the coating to a hydromagnesite-aragonite mixture with gaseous oxygen being evolved through the porous structure. Later experiments showed that the coatings can thicken at the rate of 5 cm per year. As long as current flows, the structure continues to get larger and stronger. It can also heal itself if damaged, making it particularly useful as a replacement for concrete in hard-to-access locations. High levels of dissolved oxygen make it particularly attractive to marine organisms, particularly fin fish. Hilbertz originally called his invention, on which he had several patents, underwater mineral accretion or accretion for short. The term biorock wasn't coined until later. Hilbertz’s original plan was to use this technology to grow low-cost structures in the ocean for developing countries. He also envisioned accreting large aquadynamic OTEC ocean thermal energy conversion plants, both for generating power and for producing hydrogen, ammonia, and magnesium hydroxide.〔Hilbertz, W. H. et al., "Electrodeposition of Minerals in Sea Water: Experiments and Applications", ''IEEE, Journal of Oceanic Engineering'', Vol. 4, No. 3, pp. 94-113, July 1979〕 This appeared to result in a building process largely independent of land-based resources. His focus shifted to coral reefs after meeting Dr. Thomas J. Goreau in the 1980s. They formed a long-standing partnership, with Goreau continuing work on biorock technologies and coral reef restoration after Hilbertz' death in 2007. Because the biorock process uses such simple materials, electrode forms can be constructed in a variety of shapes to mimic natural reefs. Since the combined hydrated magnesium oxychloride, brucite (magnesium hydroxide) - later hydromagnesite (magnesium chlorocarbonate) and aragonite (calcium carbonate) coating that forms is so similar to natural reef substrate, corals take to biorock reefs very readily. Countless projects over the years have demonstrated that coral thrive on the electrified and oxygenated reef environment. One prominent example was in the Maldives during the 1998 warming, during which fewer than 5% of the natural reef corals survived. On biorock reefs in the area, 80% of corals not only survived, they flourished.〔Goreau, T. J, ''A Solution for Corals in Peril, A GCRA Overview'', GCRA website, April 2002〕 With others, Hilbertz and Goreau made two expeditions to the Saya de Malha bank in 1997 and 2002. Using Biorock technology, they attempted to grow an artificial island around steel structures that were anchored to the sea floor.〔(PDF of the Saya de Malha expedition 2002, rev. 1 )〕 As "Seacrete" the process was substantially publicised in a 1992 book of futurology, The Millennial Project. The author, Marshall Savage, reiterated Hilbertz' earlier proposal that the conductive metal magnesium be extracted from ocean water, and that the process use electricity from ocean thermal energy conversion. In 2012, both Dr. Goreau and Robert K. Trench, writing together with Goreau, published works on how Biorock technologies could be implemented for generating building materials as well as restoring damaged ecosystems.〔Goreau T.J., 2012, ''Marine Electrolysis for Building Materials and Environmental Restoration'', ''http://www.intechopen.com/books/electrolysis/marine-electrolysis-for-building-materials-and-environmental-restoration''〕 〔T. J. Goreau & R. K. Trench (Editors), 2012, ''Innovative Methods of Marine Ecosystem Restoration''; http://click.bsftransmit1.com/ViewInBrowser.aspx?pubids=9009|8804|617373|65313&digest=Trwjk8HjfBU2iCoETuPkbA&sysid=1〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Biorock」の詳細全文を読む スポンサード リンク
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