Thomas J. Goreau, 2012
p. 273-290 in Electrolysis, J. Kleperis & V. Linkov (Eds.), InTech Publishing, Rijeka, Croatia
Additional information is available at the end of the chapter http://dx.doi.org/10.5772/48783
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. Seawater electrolysis for galvanic protection can use sacrificial anodes, driven by the voltage potential difference between different metals, or actively impressed currents driven by a battery or a direct current power supply. In the first case the voltage differences are small, usually only tenths of a volt, according to the difference in electromotive potentials of the various metals or alloys used. The metal acting as the cathode is completely protected from rusting and corrosion as long as the electrical current flows. The metal acting as the anode usually dissolves away as the reaction proceeds, and needs to be periodically replaced in order to continue to prevent corrosion of the cathode. Increased currents accelerate reaction rates, which can cause mineral growth or scale, something most uses of cathodic protection wish to avoid. For example, if a boiler is being cathodically protected from rusting, one does not want to precipitate a mineral scale layer on it, because that is less thermally conductive than the metal, and reduces heat transfer and boiler efficiency. Therefore most uses of cathode corrosion protection use the lowest possible voltages and currents needed to prevent rusting, in order to avoid growth of scale.
There is a “natural” analog of cathode protection that is crucial for marine archaeology. A shipwreck invariably contains objects of several different metals, such as various steel alloys, copper, brass, bronze, aluminum, and others. The metal that acts as the strongest anode, according to its electromotive potential, proceeds to dissolve, releasing electrons that flow to the cathode metals, protecting them from oxidation. When the anode has completely dissolved, the next metal in the electromotive series then plays that role until there are no more anodic metals left, and at that point corrosion can take place on the last cathode metal. The process causes growth of limestone scale on the cathode, which protects and conceals it. Metal artifacts preserved in marine shipwrecks have been protected because they acted as cathodes. Despite the popular image of treasure hunters finding shiny golden coins, in fact the treasure is completely encrusted in limestone, appearing as irregular white crystalline lumps with the metal surface completely concealed. The first thing marine archaeologists do with these lumps is to throw them into an acid bath to dissolve away the limestone, in some cases speeding the process up by wiring them up as an anode of a battery, although that risks destroying the artifact if it proceeds too far. Only once the limestone has dissolved can the archaeologist see the metal artifact.
Later applications of aquatic electrolysis included making chlorine and bleach (sodium hypochlorite) from seawater and chloride brines, and purification of metals, but largely under highly controlled conditions in limited volumes, often from fused salts or acid solutions rather than from seawater. Following the First World War, the Nobel Prize winning German Jewish chemist, Fritz Haber, whose work on industrial nitrogen fixation via the Haber-Bosch process is the basis for almost all fertilizer nitrogen production, and hence for our global food supplies, sought to use electrolysis of sea water to extract traces of gold from the ocean to pay back war reparations imposed by the victors. He found that concentrations were too low to be economic, and was then hounded to death by the Nazis.
2. Physical properties of mineral production from sea water
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.
Higher currents caused the growth of the mineral brucite, or magnesium hydroxide, which is soft and tends to easily break off. 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 overgrowth of undamaged sections.
The remarkable property of self-healing structures results from the distribution of the electrical field. Initially the electrical gradient between the anode and the cathode results in growth of mineral layers all over the cathode, starting at the closest points, or at sharp extremities that focus electrical field gradients, or at sites where water currents preferentially transport electrons.
Unlike the steel, the minerals are poor electrical conductors, and act as partial insulators. Nevertheless, electrons continue to flow because of the imposed electrical gradient. Although the electrolytic reactions generate hydroxyl ions and alkalinity in the water that are neutralized by mineral deposition taking place at the surface of the metal (see next section), production of hydrogen gas at the cathode surface causes creation of tiny pores and channels from the metal surface to the seawater, out of which hydrogen bubbles emerge (such bubbling provides visible proof that the reaction is working properly). Even Biorock material with three times the load-bearing strength of ordinary concrete has around 20% porosity. While it might be thought that minerals might insulate the cathode and prevent further growth, the imposed electrical gradient ensures that growth continues, in part because electrons flow through the hydrogen escape pores. We observe no long-term decrease in the rate of bubbling or the growth of minerals, even in cases where more than 30 cm of hard minerals have grown over the cathode.
When the mineral growth is broken off, whether by severe storm wave damage, boat impacts, or deliberately by pliers, hammers, or hacksaws, and the bare metal is exposed, there is greatly increased growth at that point, until the newly deposited minerals are as thick as adjacent unbroken material. The metal is all at the same voltage potential, but reduced or absent mineral coatings cause the increased electrical current and mass transfer to flow through the water at that point. When the newly grown material is as resistive as the old coating the increased growth rate is self-limiting. In some cases new material is more porous due intense hydrogen bubbling, and the repaired area may grow thicker than adjacent harder and less porous material. We first recognized this focusing of current to freshly exposed surfaces in an experiment using multiple lengths of rebar as cathodes. We would periodically remove one rebar in order to measure the thickness of the material growth, replacing it with a fresh rebar, in an attempt to measure long-term growth rates and changes in chemical composition. The bare steel surface focused the current on the new rebar, which grew at the expense of all the others, stopping their growth. While the experiment did not work as intended, it provided valuable insight into the process.
This paper is a synthesis of the key messages from the individual papers written by the Blue Planet Laureates (Annex I describes the Blue Planet Prize), and discusses the current and projected state of the global and regional environment, and the implications for environmental, social and economic sustainability. It addresses the drivers for change, the implications for inaction, and what is needed to achieve economic development and growth among the poor, coupled with environmental and social sustainability, and the imperative of action now. The paper does not claim to comprehensively address all environment and development issues, but a sub-set that are deemed to be of particular importance.
We have a dream – a world without poverty – a world that is equitable – a world that respects human rights – a world with increased and improved ethical behavior regarding poverty and natural resources – a world that is environmentally, socially and economically sustainable, where the challenges such as climate change, loss of biodiversity and social inequity have been successfully addressed. This is an achievable dream, but the current system is deeply flawed and our current pathway will not realise it.
Population size and growth and related consumption patterns are critical elements in the many environmental degradation and social problems we currently face. The population issue should be urgently addressed by education and empowerment of women, including in the work-force and in rights, ownership and inheritance; health care of children and the elderly; and making modern contraception accessible to all.
There is an urgent need to break the link between production and consumption on the one hand and environmental destruction on the other. This can allow risking material living standards for a period that would allow us to overcome world poverty. Indefinite material growth on a planet with finite and often fragile natural resources will however, eventually be unsustainable. Unsustainable growth is promoted by environmentally-damaging subsidies in areas such as energy, transportation and agriculture and should be eliminated; external environmental and social costs should be internalized; and the market and non-market values of ecosystem goods and services should be taken into account in decision-making.
The immense environmental, social and economic risks we face as a world from our current path will be much harder to manage if we are unable to measure key aspects of the problem. For example, governments should recognise the serious limitations of GDP as a measure of economic activity and complement it with measures of the five forms of capital, built, financial, natural, human and social capital, i.e., a measure of wealth that integrates economic, environmental and social dimensions. Green taxes and the elimination of subsidies should ensure that the natural resources needed to directly protect poor people are available rather than via subsidies that often only benefit the better off.
The present energy system, which is heavily dependent on fossil fuels, underlies many of the problems we face today: exhaustion of easily accessible physical resources, security of access to fuels, and degradation of health and environmental conditions. Universal access to clean energy services is vital for the poor, and a transition to a low carbon economy will require rapid technological evolution in the efficiency of energy use, environmentally sound low-carbon renewable energy sources and carbon capture and storage. The longer we wait to transition to a low carbon economy the more we are locked into a high carbon energy system with consequent environmental damage to ecological and socio-economic systems, including infrastructure.
Emissions of GHG emissions are one of the greatest threats to our future prosperity. World emissions (flows) are currently around 50 billion tonnes of carbon dioxide-equivalent (CO2e) per annum and are growing rapidly. As the terrestrial and oceanic ecosystems are unable to absorb all of the world’s annual emissions, concentrations (stocks) of GHG emissions in the atmosphere have increased, to around 445ppm of CO2e today and increasing at a rate of around 2.5ppm per year. Thus we have a flow-stock problem. Without strong action to reduce emissions, over the course of this century we would likely add at least 300 ppm CO2e, taking concentrations to around 750 ppm CO2e or higher at the end of the century or early in the next. The world’s current commitments to reduce emissions are consistent with at least a 3oC rise (50-50 chance) in temperature: a temperature not seen on the planet for around 3 million years, with serious risks of 5oC rise: a temperature not seen on the planet for around 30 million years. Given there are some uncertainties present in all steps of the scientific chain (flows to stocks to temperatures to climate change and impacts), this is a problem of risk management and public action on a great scale.
Biodiversity has essential social, economic, cultural, spiritual and scientific values and it’s protection is hugely important for human survival. The rapid loss of biodiversity, unprecedented in the last 65 million years, is jeopardising the provision of ecosystem services that underpin human well-being. The Millennium Ecosystem Assessment concluded that 15 of the 24 ecosystem services evaluated were in decline, 4 were improving, and 5 were improving in some regions of the world and in decline in other regions. Measures to conserve biodiversity and make a sustainable society possible need to be greatly enhanced and integrated with social, political and economic concerns. There is a need to value biodiversity and ecosystem services and create markets that can appropriate the value for these services as a basis for a ‘green’ economy.
There are serious short-comings in the decision making systems at local, national and global levels on which we rely in government, business and society. The rules and institutions for decision making are influenced by vested interests, with each interest having very different access over how decisions are made. Effective change in governance demands action at many levels to establish transparent means for holding those in power to account. At the local level public hearings and social audits can bring the voices of marginalized groups into the forefront. At national level, parliamentary and press oversight are key. Globally, we must find better means to agree and implement measures to achieve collective goals. Governance failures also occur because decisions are being made in sectoral compartments, with environmental, social and economic dimensions addressed by separate, competing structures.
Decision makers should learn from ongoing grass-root actions and knowledge in areas such as energy, food, water, natural resources, finance and governance. This is key, not the least in rural communities with a view to their management, control and ownership of these resources. There is a need to scale-up the grass roots actions by bringing together a complementary top-down and bottom-up approach to addressing these issues. Global cooperation can be improved by building on on-going regional cooperation to deal with common sustainable development issues.
Effective training programs should be implemented to multiply the number of competent decision makers in business and government. They must learn how to integrate programmes and policies within sustainability constraints, to understand the business case thereof, and acquire the skills to strategically move towards such sustainability goals.
All of the problems mentioned above demand we increase investments in education, research and assessments of knowledge.
If we are to achieve our dream, the time to act is now, given the inertia in the socio-economic system, and that the adverse effects of climate change and loss of biodiversity cannot be reversed for centuries or are irreversible (for example, species loss). We know enough to act, but the current scientific uncertainties, means that we are facing a problem of risk management on an immense scale. Failure to act will impoverish current and future generations.
The Tiburón Agua y Electricidad project in Mexico aims to provide thousands of megawatts of power along with enough fresh water to supply large parts of North Western Mexico and the Southwest US. It also claims it will be home to a reef-growing infrastructure that will keep sea life and fishermen happy.
By Jason Deign
Grab a map of the world and see if you can spot what is arguably the best location on the planet for tidal power. Found the Gulf of California yet? That is where Kenneth D Lampner hopes to build one of the biggest and most self-sustaining tidal projects he thinks the world has ever seen.
Specifically, Lampner, who cut his teeth in the renewable energy industry 30 years ago with Solar Integrations, a PV company he still runs, is looking at a site called Infiernillo Strait, near the Mexican town of Bahia Kino, in Sonora.
The shallow Strait runs between the mainland and Tiburón Island, which partially blocks the Gulf and creates a choke point for incoming and outgoing tides. “What’s different about my project is the location,” Lampner says. “It’s a river in the ocean.”
Under a project being permitted by the Mexican Comisión Federal de Electricidad, Lampner aims to tap the three-metre tidal surge at both ends of the Strait to create an estimated 1,500 to 5,000 MW of power an hour.
This output is expected to be fairly constant as it takes the tide about seven hours to fill the Tiburón basin on the far side of the island, and about five hours to drain from it, besides there being a time lapse between the southern and northern ends of the Strait.
Most of the power will be used to drive the world’s largest desalination plant, a reverse-osmosis facility with a capacity of 350,000 cubic metres per day, to provide water for nearby Hermosillo and the surrounding area, and potentially for export to parched North Western Mexico, Arizona and Southern California.
This would take advantage of a 2003 Mexican self-supply law that allows private projects to generate electricity for their own use. Any leftover energy could potentially be fed into the grid, Lampner says.
And he hopes to achieve all this without damaging the already frail ecosystem of the Gulf, a UNESCO World Heritage Site sometimes referred to as ‘the world’s largest fish trap’ which has nevertheless suffered significantly from overfishing in recent times.
The secret is a novel energy generation method that eschews the use of barriers or ‘spinners’ in favour of a vertical-axis Francis turbine design that exploits the variation in water level caused by the tides.
Lampner’s plan is to have these turbines anchored to the 12-metre seabed in the Strait but located close to the surface, so that marine life beneath them is not affected by their presence, and with channels so that fishermen and seagoing mammals can navigate between them.
The anchoring method he has chosen is as novel as his turbine design. His company, Tiburón Agua y Electricidad, has co-opted Dr Thomas Goreau, president of the Global Coral Reef Alliance, to create an infrastructure using a reef growth technique called Biorock.
With Biorock, a very low voltage current is passed through a wire frame so that minerals precipitate onto it, forming a limestone skeleton that can serve as a home to corals and other marine life.
“These are solid structures that gain strength in time and are self-repairing,” says Goreau. “The purpose is to tap surface tidal currents. We’re not trying to build a barrage, but it’s going to require support structures.”
Goreau says that if Biorock deposition happens at an optimal rate of 1-2 cm per year then “you get a structure that’s two or three times stronger than Portland cement.”
That might not be possible in the Tiburón development, he adds, because of the need to have structures that are strong from the outset.
Even if there has to be some compromise on this point, though, the continuously strengthening properties of Biorock should provide long-term benefits, and not just from an infrastructure point of view.
Organisms grow two to six times faster on Biorock than on traditional undersea substrates, Goreau says, “so we should be able to create much lusher fishing grounds.”
Besides Goreau, the Tiburón team counts Dr Chi Lin of Tianhuangping Pump Storage, which worked on the Three Gorges Dam development in China, and a number of engineering and renewable energy specialists. Lin will be responsible for sourcing the turbines from China.
Lampner, who describes himself as “being in real estate”, expects to foot most of the US$1.55bn cost of the project from investments in old goldmines, from which he hopes to extract other valuable minerals, such as silver.
Currently he is hoping to complete a detailed tidal site assessment of the Infiernillo Strait at the time of the spring high tides. But he accepts his grand design is taking time to come to fruition. “Three and a half years ago I thought I’d have it done in two years”, he says.
“I’m trying to push it as fast as I can because I’d like to see it done before I die.”
With a capital cost recovery estimate of five years for electrical generation and desalination, the project could become a viable, long-term and sustainable clean-energy franchise capable of satisfying the rapidly growing demand for water in the State of Sonora.
Total estimated project construction cost: US$1.550 billion (tidal electric generators: $750 million; power station: $250m; desalination plant: $350m; aqueduct: $150m; pumping stations: $50m).
Proposed electric project capacity: 1,500 to 5,000 MW
Andre DeGeorges 1,2,*, Thomas J. Goreau 1 and Brian Reilly 2
1 Global Coral Reef Alliance, 37 Pleasant Street, Cambridge, MA 02139, USA; E-Mail: email@example.com
2 Department of Nature Conservation, Tshwane University of Technology, Private Bag X680, 0001 Pretoria, South Africa; E-Mail: firstname.lastname@example.org
* Author to whom correspondence should be addressed: E-Mail: email@example.com; Tel.: +1-757-854-1303; Fax: +1-703-790-1578. Received: 6 August 2010; in revised form: 5 September 2010 / Accepted: 9 September 2010 / Published: 14 September 2010
Abstract: This paper discusses land-sourced pollution with an emphasis on domestic sewage in the Caribbean in relation to similar issues in the Indian Ocean and Pacific. Starting on a large-scale in the 1980s, tropical Atlantic coastlines of Florida and Caribbean islands were over-developed to the point that traditional sewage treatment and disposal were inadequate to protect fragile coral reefs from eutrophication by land-sourced nutrient pollution. This pollution caused both ecological and public health problems. Coral reefs were smothered by macro-algae and died, becoming rapidly transformed into weedy algal lawns, which resulted in beach erosion, and loss of habitat that added to fisheries collapse previously caused by over-fishing. Barbados was one of the first countries to recognize this problem and to begin implementation of effective solutions. Eastern Africa, the Indian Ocean Islands, Pacific Islands, and South East Asia, are now starting to develop their coastlines for ecotourism, like the Caribbean was in the 1970s. Tourism is an important and increasing component of the economies of most tropical coastal areas. There are important lessons to be learned from this Caribbean experience for coastal zone planners, developers, engineers, coastal communities and decision makers in other parts of the world to assure that history does not repeat itself. Coral reef die-off from land-sourced pollution has been eclipsed as an issue since the ocean warming events of 1998, linked to global warming. Addressing ocean warming will take considerable international cooperation, but much of the land-sourced pollution issue, especially sewage, can be dealt with on a watershed by watershed basis by Indian Ocean and Pacific countries. Failure to solve this critical issue can adversely impact both coral reef and public health with dire economic consequences, and will prevent coral reef recovery from extreme high temperature events. Sewage treatment, disposal options, and nutrient standards are recommended that can serve as a reference point but must be fine-tuned to local ecology.