A closed aquatic ecosystem is a sealed yet self-sustaining environment for which the only input is the sunlight that plants use to grow and purify the ecosystem. They usually contain gravel, algae, coral and but small shrimp, snails and a kind of crustacean called a copepod all do well as they can get all the nutrients they need.
The entire system usually runs for about 3–5 years before it dies. For a system that’s supposed to be sealed, changing 25% of the water once a week sounds like cheating and grounds for disqualification. Cleaning means one system is detoxified at the cost of another but it also sounds familiar. If supposedly closed systems require periodic maintenance then they’re really just systems that shift toxicity from one place to another in much the same way as refrigerators relocate heat.
A Boeing 737-800 or an Airbus A380 can stay in the air for maybe 18 hours and not only keep passengers fed and alive but comfortable and entertained for the cost of approx. 2.8 liters of fuel per passenger per 100 kilometers. Burning approximately three liters of fuel per second produces carbon dioxide and other gases and particles that we know to have an environmental cost.
A submarine is a more successful closed system. The British Royal Navy’s Astute-class nuclear-powered fleet can stay submerged and operating for 25 years until the fuel is spent. The vessels can purify air and water for 98 submariners but carry only carry food for 90 days. For a vessel that might either start or finish a global nuclear holocaust, that doesn’t seem like much. Once that 90 days plus two or three weeks is up, the submarine would still be a closed system for the next 25 years but it would be one without human life. Gaia writ small.
Cruse liners take it more leisurely and relatively economically at 0.58 lit. of diesel fuel per hour. They carry sufficient fuel to cruise for a month but it’s rare for a liner to cruise uninterrupted for more than 7–10 days as passengers would soon notice the absence of fresh fruit and vegetables.
At full power, one Harmony of the Seas combusts 1,377 US gallons (5,200 lit.) of diesel per hour. This sounds a lot but it’s the total energy required to sustain the lives and activities of 8,890 persons for one hour. In addition to the energy required to propel 225,000 tons of ship through water, desalinating sea water is energy intensive, swimming pools need filtering, drinks need ice, casinos need 24-hour bright lights. It all adds up and it’s all made possible by one pint (0.58 lit) of diesel per person per hour. Although we can compare the quantity and composition of emissions between numbers [?] of different types of transportation, a cruise liner is simultaneously a life support system while cars are not. There’s no similar isolable city or system in the world we can compare.
However, if a submarine can carry 90 days of provisions for a crew of 100 then space could be found on a modern cruise liner to store food for a population ninety times greater even if everyone didn’t eat navy rations. Any capacity beyond that would increase the amount of time the system was closed and that time is now limited by the storage of fuel not food.
Castles weren’t going anywhere so food storage was important for times of siege when they had to operate as closed systems. This is Crusader castle Krak des Chevaliers near Homs in Syria, close to the border with Lebanon.
The most famous castle siege of al time is that of Chateau Gaillard, built by Richard the Lionhearted between 1196-1198. It was a closed system for eight months when it was under siege by the forces of Philip, King of France, before surrendering on March 8, 1204 after the stone walls forming its third line of defense were breached by tunnels.
The more usual siege tactic was to cut off supplies of food and water and forcing the choice of surrender or starvation. Another trick was to catapult dead bodies over the castle walls in the hope of spreading disease. Disease and closed systems are not a good combination. On aircraft carriers, stairwell railings are a common source of germ transfer and experienced crew go up and down without touching them.
A nuclear powered aircraft carrier such as the George H.W. Bush has a crew of 6,000–7,000, can prowl the seas for 20 years without refueling and, in normal operation, carries a maximum of seventy days food. If some of the space allocated to the storage of aircraft were used for the storage of food then I’m sure it could function for at least a year as a system as closed as is possible on Earth.
Arcadia was a not-very-good movie about yet another dystopian future, in London of all places, where the well-off get to live in Arcadia, a disease-free high rise whose occupants have a high life expectancy. For me, there was too grubbing around outside the building but, even without watching it all, I don’t think a closed system on the scale of a building is going to work. Just as with castles, there are too many inputs and the three big ones of air, food and energy are all related.
Last year there was much news about a US$3 mil. price for a place inside a luxury nuclear bunker in Kansas. The 60 metre-deep building can accommodate up to 75 people. Each day, reverse osmosis can filter 10,000 gallons of water from geothermal wells but I don’t know where the energy for illumination, air purification and waste processing comes from. Good for five years, they say.
The world first saw photographs like the one on the left below in 1969 and, for many, the first time in color was the LIFE magazine special edition the same year. Some people maintained the moon landing was faked and some may still maintain the Earth is flat but the photo of the blue planet against the black background made many people appreciate that we live on a planet that is a very closed system save for the energy it receives from the Sun. Soon after in 1972, James Lovelock proposed The Gaia Hypothesis: Living organisms on the planet interact with their surrounding inorganic environment to form a synergetic and self-regulating system that created, and now maintains, the climate and biochemical conditions that make life on Earth possible.
The meanings of “synergetic”, “self-regulating” and “maintains” were never clear and haven’t become clearer in the fifty years since. A project called Biosphere 2 (because Biosphere 1 is Earth) attempted to find out. It was a closed system [known as a vivarium, I learn] consisting of seven “biomes” inhabited by eight persons for one two-year period starting 26 September 1991 and one ten-month period starting September 1994. The architecture was mid-70s space gothic and the occupants wore red jumpsuits with epaulettes. We never found out what was learned or how closed the system really was before and during the experiment. The experiment wasn’t without its problems but, all in all, it was a decent shot and two years is some sort of standing record.
I used to keep hearing about the Mars city the UAE government was building somewhere in the desert. A flurry of news items from 2017 say it was designed by Bjarke Ingels but you’d never know as it’s all standard Mars domes. It has (is to have?) laboratories and the plan includes a team living inside the city for one year to create a frame of reference for developing strategies to live on a hostile planet long-term. It’s too early to say what strategies will be developed from this Earth environment that has abundant and ambient oxygen, three times the gravity and one-thirtieth the solar radiation of Mars.
These highly publicized endurance endeavours all want you to think the future is about to happen, and that Technology is on the case for closed systems. It seems that any Mars simulation is good and relevant even if the system comes preloaded with oxygen, gravity and radiation protection. I remember hearing of some study done on that proposed reality TV Mars-shot calling for volunteers. It found that everyone would asphyxiate on day 66. If anyone’s still up for this knowing that, it says something about life on Earth.
When orbits align, it takes about 150–300 days to get to Mars in a 100% closed system and if you survive that (as well as the landing) then you get the chance to live in another 100% closed system. I don’t know why anyone would want to do that. We’ve been pretty lucky here on Earth and, until recently, haven’t even been aware we’re already living in a 100% closed system. Traveling 300 days in a hopefully closed system to start life in another when we’ve already proved ourselves incapable of sustaining the one we have doesn’t make sense. Biosphere 2 suffered an ant invasion because some ants were accidentally sealed into the system but the conditions were also right for an explosion of cockroaches.