Many sci-fi and fantasy settings have a Universally valuable commodity. In Dune there is the Spice Melange on the Universe level. But locally, on Arrakis where the Spice comes from, Water is so scarce that the natives freeze-dry their dead to capture their waters. The distribution and conservation of both of these resources has deep impacts on the economies and the cultures in the story.
Over the past week I have stumbled across a few interesting stories about the element Phosphorus:
Basically phosphorus is an essential ingredient for life. ATP powers the metabolism of all known forms on life. Your body makes 70kg of the ATP molecule per day. ATP is basically a handy way of distributing energy in the cell.
Phosphorus is rare in the Solar System and even rarer in the Universe. Essentially the amount of biomass your planet or space habitat can support is a direct function of how much phosphorus you have on hand. What makes the concentration of life in the Amazon possible is a steady stream of phosphorus in the form of dust carried on the wind from Africa.
When mankind moves out to space, phosphorus is going to place the same hard limit on the size of settlements. Humans need phosphorus as an essential mineral, of course. But we will also need to supply enough for all of the plants that have to be grown to feed both people and whatever livestock we bring along for meat and other products.
In a sealed system, phosphorus is conserved through the phosphorus cycle.
But what happens if you have a settlement that is mainly a food producer, shipping to a large city that is net food consumer? The farmland in the agriculture area will be depleted of phosphorus. That phosphorus will basically be taken up by the citizens of the urban area, and excreted as waste. One of the major industries in the city is going to have to be collecting that phosphorus from the waste, and shipping it back to the farm.
In the Sublight universe, I am creating a megalopoly called TASTE®. In the core system, (inside Mars Orbit) most food is grown on giant solar powered farms. Farms exist on the moon, and in orbit around Earth. These farms feed cities in space with millions of people. (The Earth is gradually being depopulated to turn it into a nature reserve.) TASTE® controls the food packaging industry, the fertilizer industry, and the waste management industry. Their centralized management of the element of Phosphorus has become a highly regulated industry. (After a heck of a lot of monopolistic shenanigans on their part.)
However, for all of their leverage TASTE®'s system of accounting for phosphorus is basically the only hard currency in an otherwise post-scarcity world. To buy food from TASTE you need to give them the contract to recycle your waste. And their giant factory farms and tight control over the phosphorus market mean that nobody can compete on cost or efficiency.
You get a commune here and there who are self-sufficient. But as soon as they try to trade in food or other agriculture items, they are going to run across phosphorus imbalance problems. And when they go to buy phosphorus on the open market, they are going to be in a world of hurt because TASTE® has cornered the market and jealously guards their monopoly.
In the International Space Treaty Organization, their major cities were designed as sealed systems. The city of New Franklin operates enough farms to feed the people who live there. The also have enough capacity to grow extra food to put some food aside for emergencies. With 750,000 inhabitants, the city has its own dedicated facilities for phosphorus recovery.
However, New Franklin (and for that matter, all of the stations around Psyche) have to deal with a large influx of migrants and visitors. Psyche itself has some decent pockets of phosphorus rich minerals. But those are mainly recovered as a side-product of Psyche's primary industry: nickel-steel. This is enough to make good losses in phosphorus from efficiency of recovery, tourists, migrant workers, and armed forces supplied by Psyche and deployed elsewhere in the Solar System.
Psyche itself is a sovereign state, and it jealously controls the rate at which their planet is depleted. So while they reluctantly part with some phosphorus as their contribution to the federation, they do not allow commercial exploitation of their phosphorus. They also do no ship phosphorus in bulk to other member states of the International Space Treaty Organization.
TASTE® is headquartered on its inner system space platforms. It operates as a monopoly utility in sparsely populated areas of the Solar System. In bigger cities, it makes money from license fees for its technology, consultant fees for how to operate its technology, and as overpriced contractors to clean up when big cities completely screw up their implementation of TASTE® technology.
Up until the latest upheaval in Krasnovia's government (their transition from populist facisms to constitutional dictatorship) competing ministries jealously battled for control over "the people's" phosphorus. The net result was graft, and waste, and enormous duplication of effort. The Fürer's first reform was to call in TASTE®, and have them perform a top-down reform of the system. TASTE® continues to essentially operated the Krasnovian ministries of Agriculture and Sanitation. They also have a lot of sway with the ministry of natural resources. Each Ministry is still managed by a minister who "supervises" TASTE®'s operations. But in essentially all conflicts brought before the Fürer, TASTE® normally wins.
In ISTO TASTE® operates under special monopoly power laws. They are the preferred provider for waste management and food production. Individual nations/settlements under ISTO are free to manage their own resources. TASTE®'s business model is to run the recycling and waste treatment plants, and sell the phosphorus back to the farmers while operating on government subsidized fusion energy. TASTE® also collects the waste from starships.
Other operators have tried to muscle into the sewage treatment market. But TASTE® has them beat on economies of scale. In particular, nobody can compete with them on operating costs.
Where TASTE® operates as a monopoly, there are a pile of strange rules about waste management. You can't actually purchase indoor plumbing, plumbing fixtures, or trash cans (at least the big one you put on the curb). You lease them from TASTE®. In exchange, you do get lifetime service and regular replacement. But their color and style selection is... limited.
Project Gilgamesh (under which the Paul Cézanne was built) is a collaboration between the ISTO to develop an interstellar vessel. The ship takes recycling and resource management to an extreme. TASTE® were brought in as consultants. Many of the high efficiency systems were tailored to interface with as much of the existing TASTE® line of products as possible.
During the events of the book, an armed standoff between ISTO and Krasnovia disrupts lines of communication all around the Solar System. This disruption is most felt on the planetoid of Eros. Eros is home to the "Happiest place in the Solar System", the resort of Yisned. TASTE® provides the catering and the waste disposal.
Eros has a double-whammy. Eros has had an extremely prosperous year. It's orbit took was within 1 AU of Earth's from October (2004) through July (2005). It has been awash in tourists and fresh food shipments. It does get some business from the Asteroid belt at other times, but nowhere near as much as when it's near Earth.
All of this continuous strain has overworked their waste treatment system. TASTE® had scheduled a major upgrade to the system for the next period when Eros and Earth are in opposition, and they resort does not get peak crowds. (August 2005-December 2006). What they were not counting on was a massive influx if Krasnovian armed forces who "leased" the planetoid (at gunpoint) to act as a staging base for a Naval blockade around the minor planet of Ceres.
The other minor planet in dispute is Pluto. An ISTO vessel, the Salvador Dali, was supposed to be the first of a new class of ships with better engines and a highly automated workforce. It was supposed to be ready by the time Psyche was in the right place in it's orbit to launch a mission to Pluto. However, after some space trials the Dali's new systems turned out to be a disaster.
The Paul Cézanne is a 20 year old example of the prior Van Gogh class. It was originally scheduled for a mid-life refit. It ended up being overhauled to take over for the Dali in heading to Pluto. Including next generation engines that were scavenged from the damaged battle carrier Hannah Höch. With the crises, unfolding, the launch date for the Pluto mission was pushed up by nearly two years. Both superpowers are now in a race to establish control over the Keiper Belt.
In the rush to get the Paul Cézanne out on its mission, the planners neglected to account for how much biomass is going to be required to keep the much larger crew of the Cézanne alive for 5 years. With a potential war startup up, phosphorus reserves in the Asteroid belt dried up overnight, from various agencies hoarding what would normally circulate.
And even where they could find a willing supplier, the problem became how to ship it with every vessel in ISTO being mobilized for war.
After a bit of horse trading, the Commodore of the Cézanne strikes up a deal with the governor or Eros to fix both of their mutual problems. The Cézanne has plenty of capacity to deal with Eros's backed up sewage. It just has to get cut across Krasnovian Space to bring the mighty ship to the tiny planet. As it is, Eros is also along a direct course to Pluto, AND to Ceres.
Plus, as a civilian research vessel/mobile settlement, it can enjoy innocent passage through the core system because Eros is a neutral power, and because the Cézanne is fulfilling a contract for TASTE®. And the legal contracts between TASTE® and the various agencies in Krasnovia have even more weight than international treaties, or even directive from the Fürer.
Fusion powered vessels tend to operate on one of three different fusion reactions. All of those reaction involve Deuterium. Heavy water is produced by extracting naturally occurring Deuterium from major water sources. Luna gets much of its heavy water from Earth, its settlements on the Jovian Moons, and the occasional comet that makes its way into the core system. ISTO gets its water from several asteroids that are mainly water, and from the salt-water subsurface seas on Ceres.
Only large vessels with dedicated equipment can burn heavy water in a fusion reactor directly.
Heavy Water requires a tremendous amount of energy to produce, so it is an expensive commodity.
The most popular fusion fuel for fusion propulsion uses Lithium Deuteride. Lithium is extracted from saltwater. Deuterium comes from heavy water. Together they form a powdery solid that is very easy to store. (Even if you do have to keep it away from water). Inside the reactor, neutrons collide with the Lithium, and it turns into Helium and a Tritium. The Tritium then fuses with the Deuterium which releases a lot of energy.
While LiD fusion release the bulk of its energy as neutrons, the logistics of storing a solid fuel is worth the inefficiency and extra shielding. The alternative is to keep cryogenic tanks of deuterium and helium three (as tritium is a pain to produce in bulk.) You can store heavy water, and utilize electrolysis but that requires a lot of extra energy and equipment.
LiD also has the advantage in that it can be used in open-cycle fusion reactions. Most ships employ pulsed detonation of small LiD pellets.
Ships need only a few kilograms of LiD for most journeys. This compact fuel source is easy to store, easy to ship, and has evolved into an informal currency/commodity. While not exactly rare, the stuff is not exactly cheap either. Lithium and Deuterium are both found in only trace amounts around the Solar System. LiD pellets require a tremendous amount of energy to produce. All of the energy to produce the deuterium AND all of the energy to extract the lithium.
Several asteroids are the remnants of the iron core of a failed planet. The iron/nickel extracted from those bodies has a unique crystal structure caused by the material cooling over millions of years. Components constructed from these massive crystals of Iron/Nickel are extremely strong and reliable. Shavings from this process, and other less extreme deposits can be melted down and formed into a high-nickel steel that is corrosion resistent and tolerant of extreme temperature changes without deforming.
Computer technology in the sublight universe is powered by Holographic processors. After a series of mishaps and robot insurrections, the trade in new holographic processors has become tightly regulated. Pre-regulation holographic processors are sought after for their perceived "extra power", and their the fact they can be re-sold without a permit. Several robotic platforms are built specifically around these grey-market chips. However, most of the trade is between speculators and collectors. Even non-functional chips have a market value.