German architect Wolf Hilbertz plans to use the process of electrodeposition to build a self-assembling city from the sea called Autopia Ampere.
Autopia Ampere will begin as a series of wire-mesh armatures anchored atop a sea mountain. Once in place, they will be connected to a supply of low-voltage direct current produced by solar panels. Over time, electrochemical reactions will draw minerals from the sea to the armatures, creating walls of calcium carbonate, which is what us landlubbers commonly call limestone.
Autopia Ampere will begin as a series of wire-mesh armatures anchored atop a sea mountain. Once in place, they will be connected to a supply of low-voltage direct current produced by solar panels. Over time, electrochemical reactions will draw minerals from the sea to the armatures, creating walls of calcium carbonate, which is what us landlubbers commonly call limestone. (See illustration on page 57.) In much the same way that a household sponge absorbs water, the oceans absorb CO2. By removing carbon-containing compounds from the oceans, the mineral accretion process would help reduce the buildup of CO2, which is a greenhouse gas.
The idea works in practice as well as theory. Hilbertz began modestly enough, by growing a coating of limestone on wooden piles wrapped in chicken wire at 30 piers on the coasts of Texas, Louisiana and California. He is now a visiting professor of architecture at the Hochschule fur Kunst in Bremen, Germany, and an adjunct professor at McGill University in Montreal, Canada, and he has moved on to a larger project. He invited Popular Mechanics to see a sample of his handiwork that is using the same technology to build artificial reefs off Jamaica.
Working with the Negril Coral Reef Preservation Society, Hilbertz now has five experimental reefs growing around the island. Three of the experiments use power from the shore. A fourth uses a “sacrificial anode,” in effect making a wet-cell battery from nearby seawater. The fifth runs on solar power.
As a step toward his ultimate ocean-grown city, Hilbertz has planned to grow a self-sustaining island city on Seamount Ampere, which is situated about halfway between the Madeira Islands and the tip of Portugal. If constructed, it will extend 50 ft. down to the bottom of the Atlantic in that spot. Besides shallow water, the site offers good fishing, a dependable ocean current, and polymetallic nodules on the ocean floor that contain copper, cobalt, manganese, nickel and iron.
A huge limestone dam will surround the city, Hilbertz says, and building components will be grown in the sea, as shown in the illustration (right). Solar and wind generators will furnish power. So too will a thermal energy conversion system that will extract power from temperature differences among different ocean currents.
One of the cornerstones of the new city’s economy would be “limestone farming.” The mineral accretion technique that has built reefs in the Caribbean and that could one day build marine cities could also make building components for use on land. Using appropriately shaped wire forms, the minerals deposited from seawater could grow building blocks, wall panels or complete building components just like those that would build a sea-born city, but for use on dry land.
Hilbertz envisions these products being lifted directly out of the sea into barges and ships, which could deliver them to seaports around the world. A limestone farm in the Caribbean could efficiently ship the building materials to coastal areas of North and South America, Europe and Africa, to inland North American ports on the St. Lawrence Seaway and Mississippi River systems, to most of Central Europe via the Rhine, Rhone and Danube rivers and to most of the Amazon basin in Brazil. A farm in the South Pacific could service the west coast of North and South America, and booming Pacific Rim countries.
Hilbertz also envisions others of his cities becoming centers for an undersea mining industry. The seafloor is believed to be littered with metal- and mineral-rich nodules, from which refiners in a city will produce pure metals. The fact that metals refining is an energy-intensive activity isn’t the least bit daunting. He enthusiastically describes a plan in which the sea would “grow” limestone conduits that would tap deep, slow-moving ocean currents and guide them through the blades of giant hydroelectric plants.
Whatever Hilbertz’s cities manufactured, their occupants would dine on the bounty of the sea. Wild fish would be guided into nets, and domestic fish would be raised in pens, along with cultured abalone, sea urchins, oysters, mussels and other shellfish. Useful seaweeds will be cultured, and more common vegetables would be grown in hydroponic chambers.
The fact that ocean-grown cities could stand on their own economically and become independent and self-governing entities poses what Hilbertz believes to be one of the biggest barriers to their creation. He says there is no legal precedent regarding national ownership of a newly formed island that is beyond a nation’s territorial waters.
He plans to face this issue head-on with an experiment on Skerki Bank, in the Mediterranean Sea. The bank consists of a few-hundred square yards of knee-deep water between Tunisia and Sicily. It’s in international waters, but within the area both Italy and Tunisia claim as an “Exclusive Economic Zone.”
Hilbertz hopes to start growing an island there before the end of the year. “We’ll establish our presence there and stake a claim, and see what happens. If anyone challenges us, we have lawyers ready to argue our case. We’ve had so many legal opinions that we decided just to go ahead and see what happens,” he says.
