Home / Blog / City on the Sea, Part II


City on the Sea, Part II

By Liz Clift

Editor’s Note: This is a 3-part blog on the future of seasteading, that will post on consecutive Tuesdays. Check out Part I.

Food & Water

The Velella mariculture research project is testing an unanchored drifter pen in waters between 3 and 150 miles off the Big Island of Hawai’i. The project seeks to grow fish in the open ocean without leaving an environmental footprint. The pen is placed into eddies, which move it around, and thus minimize impact compared to mariculture that takes place in a static location. Additionally, the mesh on the pen is made of brass, which eliminates biofouling, the formation of microbial layers on a surface (which can have a corrosive impact on other metals as well as decrease water flow through the area).

Vellela Project. Image from Undercurrent News Website.

Vellela Project. Image from Undercurrent News Website.

A solar-and-salt water farm in the south Australian desert provides an examination of how agriculture might be transformed. The system uses no soil, pesticides, fossil fuels, or groundwater, but does collect rainwater from its roof. The greenhouse uses seawater-soaked cardboard to regulate hot summer temperatures and solar heating in the winter to keep conditions from becoming too cold. The farm currently grows only tomato plants, which are rooted in coconut husks instead of soil. The farm uses a thermal desalination system to distill water for use. The leftover saltwater is mixed with seawater then returned to the sea once salt levels have reached a baseline. This agricultural practice could provide an ideal alternative to traditional terrestrial-based farming, and would be of particular use to a city based on water.

Abalone farming, as practiced in the Monterey Bay, may offer another solution to how food is produced for inhabitants of the floating island. Abalone, unlike many other animals raised by mariculture, are herbivores and will happily munch along on freshly harvested kelp while living under piers, wharfs, or similar structures.

Monterrey Abalone Company, open water abalone farming

Monterrey Abalone Company, open water abalone farming

Seaweed is quickly becoming a trendy food—even when it’s not holding together some sushi! A cookbook released late last year offers beautiful photography (and probably really tasty recipes; I live inland and so don’t partake in the seaweed revelry like I might if I lived on a coast, even though notably many of the recipes do call for dried seaweed) and makes the argument that seaweed, when responsibly harvested, is one of the world’s most sustainable and nutritious food choices.

Several of the conceptual floating cities on the Seasteading Institute’s website featured biodomes (it wasn’t just a bad 90s movie!) or biospheres. Biodomes, or other greenhouses, dedicated to growing food crops could also provide a number of jobs, and could be set up as aquaponic systems or more traditional agriculture systems, using technology similar to the tech that’s been put in place by the south Australian greenhouse mentioned above. In addition, these spaces could also act as living classrooms for students since on a floating island space is likely to be limited!

Green roofs (which could allow people to garden) and water capture also offer opportunities for sustainable food and water use on a floating city. Green roofs also contribute to thermoregulation of the buildings upon which they rest, and can be used to produce food, recreational space, or to keep beneficial insects, such as pollinators. Roof space also provides an opportunity for water catchment, particularly during storm events. While this water could be processed to make it potable, it could also be used to help maintain garden systems, used for greywater within the household (i.e. – to flush a toilet), or be channeled through pipes as part of a cooling system.


It’s tempting to think that when we flush the toilet (throw something in the trash/composter/recycling bin) it just disappears. This is one of the tricks of living in a society that makes a lot of the work of cleaning up waste invisible (after all, landfills and waste water treatment plants are often out of sight and out of mind, as are the people who move our waste). However, things like composting toilets, or just plain composting provide options for sustainably dealing with waste. In addition, filter feeders such as oysters and clams could be used as part of a water treatment process (though, depending on what exactly these bivalves filtered—and for how long they did it—they may or may not be edible afterward).

Earthships, a type of passive solar house that is built from a combination of natural and upcycled materials, were pioneered as a solution for moving “off-the-grid.” These homes provide: thermal/solar heating/cooling; electricity based on solar or wind power; contained sewage treatment; water harvest; and food production. Earthships have been integrating waste management options for decades, through indoor and outdoor water treatment cells, and by flushing toilets using non-potable, grey water instead of fresh. Depending on the particular design of the floating city, this type of treatment plan may still be an option.

Other types of waste would also need to be considered: would this city have a way to move trash off their floating island? If they aim for higher levels of self-sufficiency, they would need to consider that—and how that alters manufacture, imports, etc. as well as become incredibly creative about re-use.

In many ways, the question of re-use in an isolated, (relatively) self-sufficient city is answered in various works of science fiction, including though certainly not limited to: young adult novels like The 100 and Across the Universe; the post-apocalyptic worlds depicted in Earth Abides, Station Eleven, The Fifth Sacred Thing, and The Dead Lands; and dystopian novels including Parable of the Sower and Parable of the Talents. Although certainly none of these books will hold the answer, science fiction has had a way of shaping our present (and likely, our future).


This is the question I’m currently most curious about. How a floating city survives a hurricane or typhoon seems perplexing—especially as I think about the onslaught of large, high waves. Would the city be able to disband temporarily and flee for safer waters, as one diagram on the Seasteading Institute indicates? Would the materials be pliable enough to withstand strong winds, while rigid enough to prevent capsizing? How would mooring the city impact this?

One design, Artisanopolis, suggests a concrete barrier that would help protect against heavy storms while also providing a recreation area. The design is modular, allowing for components of the city to be moved (via something like a tug boat), if necessary, although it is unclear if the concrete wall, which resembles a levee, would move.

Artisanopolis. From: The Seasteading Institute.

Artisanopolis. From: The Seasteading Institute.

Corrosion & Fatigue

Corrosion is a chemical reaction that ultimately weakens metallic structures—rust is a familiar example of corrosion (of iron and its alloys, which include steel). Corrosion is dependent upon the composition of the metal, pH, temperature, and other factors. The floating city—and its myriad components—would need to be designed or maintained to resist corrosion, especially since corrosion can increase on metal surfaces that have higher porosity. Protections that slow the corrosion process could include protective coatings and sacrificial anodes (metals that are designed to corrode faster) that would need to be maintained.

Fatigue relates to how “tired” a structure becomes through repeated experience with a cyclical action (like waves). For an example of how fatigue works, think about what happens as you bend a paperclip back and forth. Eventually the metal breaks (but even if it doesn’t in the moment, you know it isn’t as strong because you could feel it becoming more pliable). If the floating city was moored in some way, the design would need to include planning for fatigue of these structures in the face of ocean currents or waves.

These things, along with how the city is designed to weather storms, and how self-sufficient it is in practice will all impact how long a floating city could last. Perhaps the Rigs-to-Reefs program can provide us some insight on potential ways future floating cities would be decommissioned if that ever needed to happen—especially if components of the city are made of galvanized steel as are most O&G platforms or are otherwise designed to continue to support marine life as soon as they are installed.

In addition, better understanding how marine life adapts to man-made ocean structures could help us predict how these floating cities will interact with the ecosystem as well as provide valuable information about the impact of corrosion and fatigue on both deep water and shallow water structures. This may be especially important as different locales are determined for different floating cities—the one proposed for French Polynesia, for instance, would be located in a relatively protected bay, but deep water structures have also been proposed and would face different challenges.

Continue to Part III!

Comment Below

RSS feed for comments on this post.


Sorry, the comment form is closed at this time.