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New Hope for Coral Restoration with “Electric Reefs”?

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New Hope for Coral Restoration with “Electric Reefs”?


By Lambert Strether of Corrente.

Last year, we looked at coral and coral restoration where “coral gardeners” painstakingly reattached live coral bits to existing, damaged reefs. (Corals are honorary plants, for anyone who wants to send me pictures.) At that time, I questioned whether it was possible to “mobilize” coral gardeners for reef restoration, and whether it was or will be possible, it hasn’t happened. In this post (inspired by a reweeted thread by Sarah Taber from Interfluidity’s steve randy waldman), I want to look at a process for coral restoration that makes gardening more efficient: electric reefs[1] (a.k.a. Biorock® — the “®” is important — or mineral accretion technology). First, I’ll describe the process, then I’ll look at its utopian origins and hopes, and the financial challenges to its propagation. Then I’ll do a quick review of installations (with maps and examples). Finally, I’ll present what “the science” says.[2]

Mineral accretion technology (Biorock™) was originally invented by Wolf Hilbertz, a futurist marine biologist, and applied to coral restoration with his partner, biogeochemist and marine biologist Tom Goreau. Here, Goreau explains the process, in “Marine Electrolysis for Building Materials and Environmental Restoration.”

Within weeks after Alessandro Volta developed the battery in 1800, William Nicholson and Anthony Carlisle applied it to the electrolysis of water, producing hydrogen at the cathode and oxygen at the anode, and thereby showing that water was not an irreducible element, as had been thought, but a chemical compound made up of two elements with very different properties. It was quickly found that adding salts to the water greatly accelerated reaction rates. We now know this is caused by increased electrical conductivity and reduced resistivity, thereby increasing the electrical current flowing for a given applied battery voltage according to Ohms’s Law. Humphrey Davy soon applied electrolysis to the practical problem of oxidative corrosion of copper plates used to sheath ships and protect the wood from boring organisms, founding the field of galvanic protection of metals from corrosion, now widely used to protect steel ships, oil rigs, bridges, and subsea pipes from failure.

Michael Faraday was the first to precipitate solid minerals by electrolysis of seawater. It was not until 1976 that Wolf Hilbertz recognized that these minerals, under the right conditions, could be a resource rather than a problem to be avoided. Hilbertz, an innovative architect working on self-growing construction materials, experimented with electrolysis of sea water and discovered that by varying the voltage and current applied he could grow different minerals on the cathode, ranging from soft to hard (Hilbertz, 1979). His inspiration was biological: if marine organisms could grow shells and skeletons of precisely controlled architecture from minerals dissolved in seawater, we should be able to figure out how to do so as well. Limestone does not precipitate naturally from seawater, so marine organisms must use their metabolic energy resources in order to create special internal chemical conditions that cause shell growth.

Hilbertz found that under low electrical current conditions he could grow extremely hard calcium carbonate limestone deposits, made up of crystals of the mineral aragonite, the same compound that makes up coral skeletons and the bulk of tropical white sand beaches…. Through experimentation it proved possible to grow rock-hard limestone coatings of any desired thickness on steel frames of any desired shape or size, at up to 1-2 cm per year, with compressive (load-bearing) strength up to 80 Newtons per square millimeter (MegaPascals), or about three times the strength of concrete made from ordinary Portland Cement. This material, which Hilbertz first called “Seacrete” or “Seament”, is now called “Biorock®” in order to emphasize that this is the only GROWING marine construction material that gets larger and stronger with age, and is self-repairing, like biological materials, but unlike any other marine construction material. This unique property causes any damaged or broken portion to grow back preferentially over growth of undamaged sections.

(I quoted so much because I love the intellectual history, going all the way back to Volta). I cut Goreau off before he got to the coral part — I’ll return to that later — to get to the business aspect. Recall that Hilbertz was a futurist. His dream was to use Biorock® as a generic construction materials, to build entire cities, as shown in this visualization from the U.K.’s Government Office for Science, A visual history of the future, “Future of Cities working paper”:

New Hope for Coral Restoration with “Electric Reefs”? 1

(One can imagine Biocrete® being used in Kim Stanley Robinson’s New York 2140, if Robinson had written from a different technical premise.) Needless to say, utopian projects that do not yield a return on capital have a hard time getting funded, and that goes for coral reef restorations, let alone entire cities. Tom Goreau comments:

“As a career choice, it has been suicidal to be in a field where there is no funding — it is impossible to survive. I often wish I had not been obliged by circumstance to have to do this and could have had a job that I would be actually paid for.”

So that Goreau and Hilbertz could avoid professional suicide — or because, as Founders, they wanted to reap the reward for their invention — they patented Biocrete®. That made it possible for mineral accretion technology to survive, but made it impossible for it to thrive. From New Heaven Reef Conservation Program, “A New Future in Electric Coral Reefs“:

One of the major problems with the technology is that up until recently is has remained patented, trademarked, and proprietary information of the Biorock Company. Because of these ownership and patent restrictions, the technology has not been freely available to the reef managers and local communities who could have benefited most from its use. 19 years has essentially been lost, over which time tools that could have helped save reef areas and preserved coral diversity in places around the globe has been forestalled.

But fortunately that is changing. Many reef managers, coral restorationists, and reef scientists have been waiting for the time when the patent on the mineral accretion technology would expire so they could begin to further develop the technology and independently verify many of the claims made by its creators. Often the year 2015 has been thought to be the year in which the patent would expire, and had many of us waiting. However, according to the United States Patent and Trademark Office website (accessed on 19 August 2015) the patent (No. 5,543,034) actually expired on 1 September 2008 due to “NonPayment of Maintenance Fees Under 37 CFR 1.362”.

As a sidebar, I would note that Biocrete® and permaculture share some similarities: Both have charismatic founders (plural), and both faced the problem of propagating their ideas over the span of a lifetime while not committing career suicide. Hilbertz and Goreau solved this problem with patents and licensing; permaculture solved it with licensing and training (even to the extent of a sort of apostolic succession). Both, as we shall see, faced difficulties with “the science,” because involved site-specific, individually funded projects that were not especially amenable to replication in journal form; both were founded less byprofessionals than (biosphere) entrepreneurs.

So how many of these electric reef (mineral accretion) project are there in the world? From the Global Coral Reef Alliance (GCRA, Hilbertz and Goreau’s 501(c)(3), we see that their work has survived:

Around 500 Biorock™ reef structures have been built in around 40 countries all around the world, mostly in small islands, with around 400 of them in Indonesia with our local partners, Biorock™ Indonesia.

And in a note at the bottom of the page, we see why it has — had? — not thrived:

A warning note: Biorock™ process is elegantly simple, and easily executed by those with special training and materials, but will fail if imitated without authorized expertise and maintenance.

Here is a map, from Caspar Henderson, “Electric Reefs: The Vital Spark That Reanimates The World’s Ailing Coral Reefs May Be Electricity,” The New Scientist:

New Hope for Coral Restoration with “Electric Reefs”? 2

That map is from 2002, and seems to be the only one on the internet. Here is a map of all artificial reef projects from 2019:

New Hope for Coral Restoration with “Electric Reefs”? 3

The legend at bottom left has nothing specific for electric reefs or Biorock®, but from what we kdnow of existing projects, I think we can infer a good many of the “Other” (grey) dots are mineral accretion technology sites, especially in Southeast Asia. That’s the best I can do on maps.

So, the long-promised return to the coral part. From the Gili Eco Trust, which is restoring coral reeds in Indonesia’s Gili Islands:

Biorock is a novel technology to create an artificial coral reef. We’ve been building steel structures and attaching a low voltage of direct current through when installed to create accelerated growth of corals, with increased resistance to climate change, coral bleaching and increased storm activity.

Reef gardeners and Biorock students recover corals that have been dislodged from the reef in storms, anchor damage or poor tourist behaviour and transplant them carefully on the structures.

The low voltage current creates an electrolytic reaction and a stable substrate of calcium carbonate accretes onto the rebar causing the structure to grow in size and become heavier and anchor itself to the reef. Layers of calcium carbonate are deposited on the structures, providing a sturdy and optimal surface for corals to cement to. The low electric current also promotes the coral to grow faster and stronger than on the natural reef.

Here’s a photo of the rebar with limestone accretion after two years:

New Hope for Coral Restoration with “Electric Reefs”? 4

It’s not the accretion part that worries me. It’s the “promotes the coral to grow faster and stronger” part. From Hilbert and Goreau’s GCRA:

Because it directly stimulates the natural energy-generating mechanisms of all forms of life, GCRA’s Biorock electrical reef regeneration technology is the only method known that can grow Coral Arks to save species from extinction. Other coral restoration methods work only as long as it never gets too hot, muddy, or polluted, but the corals die from heat stroke when their temperature limits are exceeded, while most Biorock reef corals survive. The Biorock method keeps entire reefs alive when they would die, providing high coral survival when 95-99% of surrounding reef corals bleach and die from heat shock. It also grows back dead reefs and severely eroded beaches at record rates in places where there has been no natural recovery.

“Natural energy-generating mechanisms of all forms of life” strikes me as woo woo, on a par with permaculture woo woo. (Biorock’s Wikipedia entry has “citation needed” on this point, so I don’t think I missed the literature, although I’d be very happy to be corrected.) Nevertheless, the proof of the pudding is in the eating, not in the account of how the pudding came to be, so let’s look at a few examples.

First, moving in more or less reverse chronological order, India. From The Hindu, “India begins coral restoration in Gulf of Kachchi“:

The Zoological Survey of India (ZSI), with help from Gujarat’s forest department, is attempting for the first time a process to restore coral reefs using biorock or mineral accretion technology. A biorock structure was installed one nautical mile off the Mithapur coast in the Gulf of Kachchh on January 19.

Biorock is the name given to the substance formed by electro accumulation of minerals dissolved in seawater on steel structures that are lowered onto the sea bed and are connected to a power source, in this case solar panels that float on the surface.

Dr. Satyanarayana, a renowned coral expert, added that fragments of broken corals are tied to the biorock structure, where they are able to grow at least four to six times faster than their actual growth as they need not spend their energy in building their own calcium carbonate skeletons.

In 2015, the same group of ZSI scientists with the support of the Gujarat forest department had successfully restored branching coral species (staghorn corals) belonging to the family Acroporidae (Acropora formosa, Acropora humilis, Montipora digitata) that had gone extinct about 10,000 years ago to the Gulf of Kachchh. The researchers claimed that the specimens for regenerating these corals were brought from the Gulf of Mannar with the help of Tamil Nadu’s Forest Department.

(The Zoological Survey of India is India’s premier organization in zoological research.) The project is already an “academic success,” since calcification has begun, and coral growth is said to be rapid, although Covid has held up documenting the results.

A second example comes from Bali, in the village of Pemuteran. From Smithsonian, “This Coral Restoration Technique Is ‘Electrifying’ a Balinese Village“:

Pemuteran is home to the world’s largest Biorock reef restoration project. It began in 2000, after a spike in destructive fishing methods had ravaged the reefs, collapsed fish stocks and ruined the nascent tourism industry. A local scuba shop owner heard about the process and invited the inventors, Tom Goreau and Wolf Hilbertz, to try it out in the bay in front of his place.

Now, there are more than 70 Biorock reefs around Pemuteran, covering five acres of ocean floor.

One survey found that “forty percent of tourists visiting Pemuteran were not only aware of village coral restoration efforts, but came to the area specifically to see the rejuvenated reefs,” according to the United Nations Development Program. The restoration work won UNDP’s Equator Prize in 2012, among other accolades.

Twenty years is a good long run for a project. From the project site:

Dr. Suadi from Gadjah Mada University researched on projects in Pemuteran and has estimated an economic yield value of US$ 115,158/year (equal to 1,532 Billion rupiah) with 70% of participation rate of villagers in the project.

Pemuteran has a population of about 8000 people, so that’s really good money. A review of the reefs from Trip Advisor:

I’m giving this 5 stars cause its free and a real achievement for Bali. I didn’t see the entire thing but what I saw was some small outcrops of coral on man made frames and a few tropical fish. We saw this the day after the natural reef and whilst it didn’t compare to that it was still time well spent. I imagine it will get better every year.

Note also that, woo woo aside, the coral seems to have done well:

This was demonstrated during the last spike in sea water temperature, which usually leads to a phenomenon called coral bleaching. Whereas in 1998 most corals had died, this time around only 10% of the corals were affected and 2% died.

Finally, an example from Thailand, Koh Tao island, which shows not only longevity, but the difference that loosening the chains of “®” can make. From New Heaven Reef Conservation, “A New Future in Electric Coral Reefs.” I apologize for the length of the quotation, but the detail is important:

For example, in 2008 the Save Koh Tao Group, was able to rally support from 17 local dive centers and over the course of a few months raised 1 million baht (About $28,000 US) to build a Biorock ™, known as locally as Hin Fai…. It was the most money the community group ever raised or spent for their yearly projects, with most successive large artificial reef projects costing in the range of 300,000 to 500,000 Thai Baht… [V]ery little of the money spent on the project went back into the local economy, and most of it went to the licensing fee.

As a community group, the owners of the company gave Save Koh Tao a discounted licensing fee of 250,000 Thai Baht ($7,000 US). Which essentially means that we have a Biorock™, however in the end there was never anything tangible given for this single most expensive item in the project – other than a handwritten receipt… The next largest expense was for the anode material, which cost 175,000 Baht. If asked what it was, the company would reply that it is a space aged metal alloy developed by NASA. Which may be true, but a less obscure way to call it is titanium-platinum alloy. Which, interestingly, is not even the most efficient material to use, but was the metal used in the original patent from 1996. By 2008 better anode materials were available, such as the MMO Titanium-Platinum meshing available for $30 dollars [9000 Baht] a sheet on eBay.

Another large expense was the pilot-project underwater transformer, known as the Biorock™ On Location Power Supply (BOLPS). The unit cost 150,000 Baht ($4,200 US), which included no guarantee or warranty, and the on-site users were not given any training or instructions for inspecting or maintaining the unit, as everything inside was proprietary. Within 2 years it had broken down, and the company quoted $2,000 US to come over and inspect it, from an island 2 hours away.

Including the flights, expenses, and consulting fees for the Biorock™ company, a total of 703,500 Baht ($19,800 US) was paid to the Biorock™ Company for the Hin Fai Project in 2008, with only 221,800 Baht being spent locally [artificial reef (cathode) materials, labor, tools, marketing].

And now Thai ingenuity kicks in:

This shows that although the devices have previously been very expensive, they don’t have to be anymore.

Lately we have been experimenting with a new generation of mineral accretion devices that have been designed by one of our ex-students. The new units are solar powered, and have a floating anode and transformer unit. Not only is the technology smaller and much more advanced, it also features a viewing window so you can easily read the voltage and amperage being produced, and a warning indicator light for leaks or problems. In a few months he was able to create a much better and cheaper unit than the BOLPS, which was essentially a cheap battery charge in a massive steel container. Each of these experimental solar units costs around $500 US, and will power a small artificial reef or can be combined with additional units to power larger structures. He has set up a facebook page to help others learn about what he has come up with.

Those are three examples, two of which show that an Electric Reef project can be long-lived, one of them showing that it can profit the village in which it is installed, and one of them showing that the technology is cheap once the intellectual property foo-fra is stripped away. Now let’s take a look at what “the science” has to say.

I did mention woo woo? From PLOS One, “Coral restoration – A systematic review of current methods, successes, failures and future directions”, published in January of this year. Here is the section on the electric reef method:

The aim of the technique is to mimic the chemical and physical properties of reef limestone, by encouraging the precipitation of calcium and magnesium on artificial substrata [98]. A direct electrical current is established between electrodes, and calcium carbonate and magnesium hydroxide precipitates at the cathode, while oxygen and chlorine are produced at the anode [99]. The purpose of this mineral accretion is to potentially increase the calcification of coral polyps, thereby boosting colony growth and resilience to stressors. The technique has been controversial and experiments attempting to verify its effectiveness have had varied outcomes. Sabater and Yap [100] described increased growth and attachment in P. cylindrica fragments when connected to a setup similar to that described by Goreau and Hilbertz [101]. A range of other studies have described increased survival of fragments on mineral accretion frames [102–106]. However, multiple experiments have failed to describe similar positive effects of exposing coral fragments to an electrical field. For example, Romatzki [107] found that A. pulchra and A. yongei coral fragments exposed to similar strength electrical currents as those described by previous researchers grew slower than control colonies. Similarly, Borell [108] described negative effects on growth of one species of coral (A. yongei) but positive effects on another (A. pulchra) growing on a cathode, suggesting that results may vary even between congeneric coral species. The disagreement between studies prohibits clear conclusions about the mineral accretions method.

I looked at [107] and [108]. Although the articles are paywalled, both studies seem to be testing the effects of electric current on coral by itself (which reminds me of the Covid studies that test a drug in a hospital setting when its use case is prophylaxis). I grant that — like permaculture — the studies may be equivocal, but I think happy villagers would regard that as of little relevance. I myself would be more persuaded with a case study that showed an electric reef that failed, even though the project “did everything right.”[3]

I also read through all the other methods, most of which were damned, only a few being blessed, and I note that — given the improvements in technology and business practice pioneered in Koh Tao — Electric Reefs were the only approach that did not require, well, NGOs, international funding, and very large grants. Koh Tao’s approach required the ability to weld rebar, the ability to build or buy floating solar panels, knowledge of local coral and water conditions, and a committed village. I don’t say that would [genuflects] “scale” to the Great Barrier reef, but it would surely work along many, many coastlines in the Indian Ocean, the Andaman Sea, and the Malaysian and Indonesian archipelago. So if that is your vision of mobilization, Electric Reefs are the technology for you[4]. And maybe one day we can build cities by mineral accretion, too!


[1] Taber has “Electrified Reefs,” which is technically more correct, but connotes for me an electrified fence, as in a prison complex. Besides, “eLECtric REEF” is iambic.

[2] Typically in my biospheric perambulations, I give definitions and classifications systems for my topic, which I here relegate to a note. NOAA defines a coral reef as: “[A] wave-resistant structure resulting from cementation processes and the skeletal construction of hermatypic corals, calcareous algae, and other calcium carbonate-secreting organisms.” Coral.org classifies coral reefs as follows:

Scientists generally divide coral reefs into four classes: fringing reefs, barrier reefs, atolls, and patch reefs.

Fringing reefs grow near the coastline around islands and continents. They are separated from the shore by narrow, shallow lagoons. Fringing reefs are the most common type of reef that we see.

Barrier reefs also parallel the coastline but are separated by deeper, wider lagoons. At their shallowest point, they can reach the water’s surface forming a “barrier” to navigation. The Great Barrier Reef in Australia is the largest and most famous barrier reef in the world.

Atolls are rings of coral that create protected lagoons and are usually located in the middle of the sea. Atolls usually form when islands surrounded by fringing reefs sink into the sea or the sea level rises around them (these islands are often the tops of underwater volcanoes). The fringing reefs continue to grow and eventually form circles with lagoons inside.

Patch reefs are small, isolated reefs that grow up from the open bottom of the island platform or continental shelf. They usually occur between fringing reefs and barrier reefs. They vary greatly in size, and they rarely reach the surface of the water.

NOAA (naturally) has not four but three (they leave out “patch reefs”). Others have five. Interestingly, the first to come up with the fringing/barrier/atoll typology was Charles Darwin, who concieved the idea during his voyage on the Beagle.

[3] The article also makes this point:

To date, the relatively young field of coral restoration has been plagued by similar ‘growing pains’ as ecological restoration in other ecosystems. These include 1) a lack of clear and achievable objectives, 2) a lack of appropriate and standardised monitoring and reporting and, 3) poorly designed projects in relation to stated objectives. Mitigating these will be crucial to successfully scale up projects, and to retain public trust in restoration as a tool for resilience based management.

[4] Of course, “technology” is not the only requirement for mobilization. From Marine Environmental Research, “Overview and trends of ecological and socioeconomic research on artificial reefs”:

The science of artificial reefs is responding to new challenges with an increase in more elaborate techniques, such as the use of remotely-operated submarines, organic indicators, isotopes, and molecular biology, while research that evaluates the socioeconomic aspects of artificial reefs is lacking. There are many aspects that deserve more research attention, such as the use of alternative inert materials, environmental impact assessment and mitigation, and analysis of conflicts with affected fisheries communities. The greater challenge is to overcome the apparent division between theory vs. application and to include robust management models of these artificial environments.

Oddly, or not, PLOS One doesn’t mention these issues.


While researching for this post, I read Treehugger’s “8 Creative Techniques to Keep Coral Reefs Alive,” and I felt I had to share this:

“Healthy coral reefs are remarkably noisy places — the crackle of snapping shrimp and the whoops and grunts of fish combine to form a dazzling biological soundscape,” Stephen D. Simpson, a marine biology professor at the University of Exeter and a senior author of the study, said in a university press release. “Reefs become ghostly quiet when they are degraded, as the shrimps and fish disappear, but by using loudspeakers to restore this lost soundscape, we can attract young fish back again.”

It’s like driving away teenagers with classical music, but in reverse!

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