A German architect has a plan to solve housing shortages, generate wealth and absorb carbon dioxide by
building new land from the sea using "mineral accretion":
A cargo ship drops anchor in choppy water 300 miles off the coast of North Africa. With practiced efficiency, its crew deploys the ship's crane and begins hauling house-size wire frames and reels of thick electrical cable from the hold. As quickly as this cargo appears topside, it is flung overboard, disappearing into the gray, swirling sea. When the decks are finally clear, the crew begins assembling floating solar panels that look like adult-size tinkertoys. The ship's engines rumble as the first of these ungainly structures is hoisted skyward and carefully deposited alongside. The activity continues until they form a vast spiral that dips below the horizon as the ship steams away. Five years later, a luxury cruise liner drops anchor at precisely the same place. Instead of finding bobbing rafts, the passengers lining its decks see the thriving island of 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.
One of the cornerstones of the new city's economy would be "limestone farming." ... 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.
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.