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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. Wolf Hilbertz developed the process and patented it in 1979.[1] 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.


Aragonite in tube

Artificial reefs have been built since the 1950s using materials including sunken ships, concrete blocks and discarded tires. However, most of these plans failed to provide coral habitat. Most notoriously, tires were strapped down off the shore of Fort Lauderdale and became an environmental disaster.[2] Some artificial reefs succeeded, but most remain relatively barren compared with natural reefs.

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 accrete around the cathode, eventually coating the electrode with a material similar in composition to magnesium oxychloride cements and as strong as concrete. Over time cathodic protection replaces the negative chloride ion (Cl-) with dissolved bicarbonate (HCO3-) to harden the coating to a hydromagnesite-aragonite mixture with gaseous oxygen evolving 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 grow and strengthen. It can 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 obtained several patents, underwater mineral accretion or accretion for short. 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.[3] This appeared to result in a building process largely independent of land-based resources.

His focus shifted to coral reefs after meeting Thomas J. Goreau in the 1980s. They formed a partnership. Goreau continued 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 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 readily take to biorock reefs. 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 there, 80% of corals flourished.[4]

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.[5] As "Seacrete" the process was publicised in a 1992 book of futurology, The Millennial Project. 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 Goreau and Robert K. Trench, writing together with Goreau, published works on how Biorock could generate building materials as well as restoring damaged ecosystems.[6][7]


Applying a low voltage electric current (safe for swimmers and marine life) to a submerged, conductive structure causes dissolved minerals in seawater, principally calcium, magnesium and bicarbonate to precipitate and adhere to that structure. The result is a composite of brucite hydromagnesite and limestone with mechanical strength similar to concrete. Derived from seawater, this material is similar to the composition of natural coral reefs and sand beaches.

Biorock structures can be built in any size or shape depending only on the physical makeup of the sea bottom, wave, current energies and construction materials. They are well suited for remote, third world sites where exotic building materials, construction equipment and appropriately skilled labor are not available.

Constructing a reef[edit]

A newly construct Biorock reef set up by Gili Eco Trust in Indonesia.

To build a biorock reef, a welded, electrically conductive frame, often made from construction grade rebar or wire mesh, is submerged and attached to the sea bottom. A low voltage direct current is applied. This initiates an electrolytic reaction that precipitates mineral crystals naturally found in seawater, mainly calcium carbonate and magnesium hydroxide, on the structure.

Within days, the structure takes on a whitish hue as it becomes encrusted with precipitated minerals that add rigidity and strength. Electric fields, plus the shade and protection offered by the metal/limestone frame, attract colonizing marine life, including fish, crabs, clams, octopus, lobster and sea urchins.

Once the structure is in place and minerals begin to coat the surface, the next phase of reef construction begins. Divers transplant coral fragments from other reefs, attaching them to the ark’s frame. Immediately, these coral pieces begin to bond to the accreted mineral substrate and because of evolved oxygen and the electrochemically facilitated accretion of dissolved ions, such as bicarbonate - start to grow—typically three to five times faster than normal. Soon the reef takes on the appearance and utility of a natural reef ecosystem rather than a man-made one.

Electrolysis of biorock reefs enhances coral growth, reproduction and ability to resist environmental stress.[citation needed] Coral species typically found on healthy reefs gain a major advantage over the weedy organisms that often overgrow them on stressed reefs. In tests where the electric current is interrupted, mineral accretion stops and seaweed begins to cover the corals. If the current is maintained, coral reef habitats can often be restored even in areas where water quality would prevent their recovery by any other method.

Biorock reefs grow rapidly and strengthen as they age. They thus have great potential for many applications, such as making breakwaters. If waves or colliding ships cause damage, renewed accretion makes them, to an extent, self-repairing.

Technical specifications[edit]

Biorock accelerates growth on coral reefs by as much as fivefold and increases coral survival.[citation needed] Biorock can enable coral growth and regrowth even in the presence of environmental stress such as thermal pollution, i.e. increasing water temperatures. When mixed with construction aggregates, it can build components on the sea floor or on land. Biorock represents the only known method that can sustain and grow natural coral species using only basic conducting elements, typically of a common metal such as steel.

Biorock samples range in compressive strength from 3720 to 5350 lbf/in² (26 to 37MPa) – for comparison, the concrete typically used in sidewalks has a strength of about 3500 lbf/in² (24 MPa).

Main components of biorock include magnesium hydroxide and calcium carbonate. This composition is chiefly the result of the ionic composition of seawater.[3] One kilowatt hour of electricity accretes about 0.4 to 1.5 kg (0.9 to 3.3 lb) of biorock, depending on parameters such as depth, electric current, salinity and water temperature.[8][9]

Biorock is cost-effective, requiring only metal bars or equivalent and electricity. While electricity provided from fossil fuels generates CO2, biorock projects often use renewable solar power, wind power, tidal power, or wave power. The resulting material is cheaper than concrete blocks in many places, depending on electricity and cement transport costs.[10]

In one study, Porites development was compared between colonies with and without an electric field for 6 months. The electric field was eliminated after the sixth month. Longitudinal growth was relatively high in the presence of the field, but dropped thereafter. Growth differences were significant only during the first 4 months. Girth growth differences were significant in the early months. The treatment corals survived at a higher rate.[11]


As of 2011, biorock coral reef projects had been installed in over 20 countries, in the Caribbean, Indian Ocean, Pacific and Southeast Asia. One project is located on one of the most remote and unexplored reef areas of the world, the Saya de Malha Bank in the Indian Ocean.[12] Other biorock projects are located in French Polynesia, Indonesia, Maldives, Mexico, Panama, Papua New Guinea, Seychelles, the Philippines and Thailand. Indonesia has the most biorock projects, with sites near over half a dozen islands, including the world's two largest reef restoration projects: Pemuteran with the Karang Lestari and the Gili islands with the Gili Eco Trust.[13] Non-coral biorock projects have been conducted in places such as Barataria Bay, Galveston, seagrasses in the Mediterranean, oyster reefs and salt marshes in New York City, in Port Aransas, and in St. Croix.


On Vabbinfaru island in the Maldives, a 12-meter, 2 ton steel cage called the Lotus was secured on the sea floor. As of 2012, coral was so abundant on the structure that the cage is difficult to discern. The 1998 El Nino killed 98% of the reef around Vabbinfaru. Abdul Azeez, who led the Vabbinfaru project, said coral growth on the structure is up to five times that of elsewhere. A smaller prototype device was in place during the 1998 warming event and more than 80% of its corals survived, compared to just 2% elsewhere.[14] However, power is no longer supplied to the project, leaving it vulnerable to the next round of bleaching.


  1. ^ US patent 4246075, issued 1981-01-20 
  2. ^ Skoloff, Brian (2007-02-17). "Tire reef off Florida proves a disaster". Retrieved 2018-08-12.
  3. ^ a b Hilbertz, W. H.; et al. (July 1979). "Electrodeposition of minerals in sea water: Experiments and applications". Journal of Oceanic Engineering. 4 (3): 94–113. Bibcode:1979IJOE....4...94H. doi:10.1109/JOE.1979.1145428.
  4. ^ Goreau, T. J, A Solution for Corals in Peril, A GCRA Overview, GCRA website, April 2002
  5. ^ "PDF of the Saya de Malha expedition 2002, rev. 1" (PDF).
  6. ^ Goreau, Thomas J. (2012-10-17). "Marine Electrolysis for Building Materials and Environmental Restoration". Electrolysis. InTech. doi:10.5772/48783. ISBN 9789535107934. Retrieved 2018-08-12.
  7. ^ Goreau, Thomas J.; Trench, Robert Kent (2012-12-04). Innovative Methods of Marine Ecosystem Restoration. CRC Press. CRC Press. ISBN 9781466557734. Retrieved 2017-10-06.
  8. ^ Ortega, Alvaro (1989). "Basic Technology: Mineral Accretion for Shelter. Seawater as a Source for Building" (PDF). MIMAR Architecture in Development. 32: 60–63.
  9. ^ Balbosa, Enrique Amat (1994). "Revista Arquitectura y Urbanismo". 15. Cite journal requires |journal= (help) no. 243
  10. ^ Goreau, Thomas; Hilbertz, W (2005-01-01). "Marine ecosystem restoration: Costs and benefits for coral reefs". World Res. Rev. 17: 375–409.
  11. ^ Sabater, Marlowe G.; Yap, Helen T. (November 2004). "Long-term effects of induced mineral accretion on growth, survival and corallite properties of Porites cylindrica Dana". Journal of Experimental Marine Biology and Ecology. 311 (2): 355–374. doi:10.1016/j.jembe.2004.05.013. ISSN 0022-0981.
  12. ^ Gutzeit, Frank + Hilbertz, W. H. + Goreau, T. J., Saya de Malha Expedition, March 2002, Sun&Sea e.V. Hamburg, August 2002
  13. ^ Goreau, T. J, comments quoted in Independent Study Project on Biorock, GCRA website, February 2011
  14. ^ Vince, Gaia (6 September 2012). "How can we save our dying coral reefs?". BBC. Retrieved 2018-08-12.

Published works[edit]

  • Hilbertz, W. H., Marine architecture: an alternative, in: Arch. Sci. Rev., 1976
  • Hilbertz, W. H., Mineral accretion technology: applications for architecture and aquaculture with D. Fletcher und C. Krausse, Industrial Forum, 1977
  • Hilbertz, W. H., Building Environments That Grow, in: The Futurist (June 1977): 148-49
  • Hilbertz, W. H. et al., Electrodeposition of Minerals in Sea Water: Experiments and Applications, in: IEEE Journal on Oceanic Engineering, Vol. OE-4, No. 3, pp. 94–113, 1979
  • Ortega, Alvaro, Basic Technology: Mineral Accretion for Shelter. Seawater as a Source for Building, MIMAR 32: Architecture in Development, No. 32, pp. 60–63, 1989
  • Hilbertz, W. H., Solar-generated construction material from sea water to mitigate global warming, in: Building Research & Information, Volume 19, Issue 4 July 1991, pages 242 - 255
  • Hilbertz, W. H., Solar-generated building material from seawater as a sink for carbon, Ambio 1992
  • Balbosa, Enrique Amat, Revista Arquitectura y Urbanismo, Vol. 15, no. 243, 1994
  • Goreau, T. J. + Hilbertz, W. H. + Evans, S. + Goreau, P. + Gutzeit, F. + Despaigne, C. + Henderson, C. + Mekie, C. + Obrist, R. + Kubitza, H., Saya de Malha Expedition, March 2002, 101 p., Sun&Sea e.V. Hamburg, Germany, August 2002
  • Cervino, J.M. + Hayes, R.L. + Honovich, M. + Goreau, T.J. + Jones, S. + Rubec, P.J., Changes in zooxanthellae density, morphology, and mitotic index in hermatypic corals and anemones exposed to cyanide, In: Marine Pollution Bulletin 46, 573–586, May 2003
  • Goreau, T. J. + Hilbertz, W. H., Marine Ecosystem Restoration: Costs and benefits for coral reefs, in: World Resource Review Vol. 17, No. 3, pp. 375–409, 2005
  • R. Vaccarella + T. J. Goreau, Applicazione della elettrodeposizione nel recupero die mattes di Posidonia oceanica, in: Posidonia Oceanica, pp. 93–105, Protezione ripopolazione di praterie ed utilazzione dei residui in agricoltora, Editoriale a Cura della Provincia di Bari, Servizio Politiche Comunitarie, Assessorato Risorse del Mare, Bari, Italy, 2008
  • Goreau, T. J. + Hilbertz, W. H., Bottom-Up Community-Based Coral Reef and Fisheries Restoration in Indonesia, Panama, and Palau, August 2008
  • Goreau, T. J. + Hilbertz, W. H., Reef Restoration as a Fisheries Management Tool, In: Thomas J. Goreau, Raymond L. Hayes, (2008), Fisheries and Aquaculture, [Ed. Patrick Safran], in Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford, United Kingdom, 2008
  • Strömberg, Susanna M. + Lundälv, Tomas + Goreau, T. J., Suitability of Mineral Accretion as a Rehabilitation Method for Cold-Water Coral Reefs, Journal of Experimental Marine Biology and Ecology, no. 395, pp. 153–161, 2010
  • Wells, Lucy + Perez, Fernando + Hibbert, Marlon + Clerveaux, Luc + Johnson, Jodi + Goreau, T. J., Effect of severe hurricanes on Biorock Coral Reef Restoration Projects in Grand Turk, Turks and Caicos Islands, Department of Environment and Coastal Resources (DECR), Grand Turk, Turks and Caicos Islands, 12-VII-2010
  • Goreau, T. J., Coral Reef and Fisheries Habitat Restoration in the Coral Triangle : The Key to Sustainable Reef Management, Proceeding of Coral Reef Management Symposium on Coral Triangle Area, pp. 244–253, Coral Reef Rehabilitation and Management Program Phase II, Jakarta Selatan, Indonesia, 2010
  • Benedetti A, Bramanti L, Tsounis G, Faimali M, Pavanello G, Rossi S, Gili JM, Santangelo G. 2011. Applying cathodically polarized substrata to the restoration of a high value coral. Biofouling 27(7): 799-809.

External links[edit]

Coordinates: 37°47′00″N 10°46′00″E / 37.7833°N 10.7667°E / 37.7833; 10.7667