Long term space occupation is currently limited by the supply chain. The ISS has to be refueled and restocked multiple times a year to keep just a few people alive and fed for small periods of time. While the cost of launching supplies is going down, such disposability of resources is not a sustainable means of developing a large space economy and society.
Food is one of the largest consumables on the space station. Comparable to, or even greater than fuel. Food is the resource that can’t be easily recycled or reused, even with modern technology. And even though there were old proposals to use human waste as radiation shielding and other such applications, these have never been implemented and most likely never will be. Space food, in its current state, also adds unnecessary bulk and weight to missions. At this point if a mission were to be launched to Mars an entire capsule would have to be stuffed with protein bars and freeze dried-spaghetti.
But food and the waste it creates can be recycled and reused, it simply requires something a bit less sterile than the systems currently in use. Space missions need to adopt a more organic means of food production and recycling in order to reduce bulk and increase reusability.
Ignoring the technical challenges for a moment, if a space garden could be implemented into a space station or capsule it would have benefits far beyond just food production and recycling. An obvious one would be the purification of air though plants’ natural processes. NASA has also performed research that proves that the cultivation of plants while in isolation, i.e. a space capsule, has positive psychological effects on humans. Plants and other living things create a connection with Earth that helps the astronauts feel more at home in space. If appropriately arranged plants would also offer the organic radiation shielding long considered by space technologists.
So that is the market. The creation of an agricultural center for a space station which can produce food and recycle the waste, while providing as many of the side benefits as possible.
Now on to the technical side of the space garden. Weight is always a concern, but one would be able to get around this by developing system that has a lifetime weight savings if it is able to produce food from seed to plate thereby reducing the cost of transportation.
Creating a garden in space is not quite as simple as just sending up some pots and putting seeds in them. If a space garden is to have maximum impact it has to have a complete cycle built into it. Astronauts plant the food, the food grows, astronauts eat the food, and then what is left is put back into the garden. While this has been a common practice on earth for millennia, in space where an entire ecosystem is difficult to create, there will have to be technological systems in place that help turn waste into compost. These could be filtering mechanisms or possibly a bio-reactor that can break down human waste to a form that is more sanitary to work with.
The system would have to be clean, one of the banes of space gardens. Too much delicate machinery has to be protected from stray dirt or water. This means that any type of garden would need to be in a self-contained module. The “module” could range in size from that of a habitat to just the size of a trunk.
Those are some basic considerations. But if the developer of such a space garden wants to maximize some of the other benefits they must go beyond a garden-in-a-box. They may want to leave food production out of it and simply create a biological recycling system. This would mean a focus on the ability of the plants to use human waste to create pure air. This could lead to something like a large tank of algae. If one were truly imaginative they might find a way to turn the algae into food. But if the psychological is the focus maybe a special type of flower would be more appropriate. A space garden can have many variations and focuses, and therefore a large potential product base.
A truly universal space garden would likely be an entire self-contained module which is something that is added to a space station and not simply parked on a shelf. This would most likely be where a young start-up would begin. Building entire gardens designed to sustain a crew with food, air, and fulfillment during a mission to Mars. Then as the space industry grows the size of the garden could be reduced in order to accommodate different missions and needs which require more variability and smaller scales.
A space garden is one of the technologies which does not need to go to space to be perfected. Plants can be chosen, tests run, and systems tested in a terrestrial environment very easily. This makes the cost of development relatively small compared to other space technologies and increases the possibility of pre-orders that can offset start-up costs.
The creation of a space garden can be far less technical than the creation of a rocket engine. But it does take a level of know-how that easily creates a competitive advantage. Sustenance farming in isolation has not been practiced in the capitalistic world for some time. The tricks of the trade may be harder to find than just a few agriculture students. But it can be done and is something that would be immensely valuable to the space industry by reducing transportation cost of food, rising moral in space, and performing cleaning of an environment that rapidly becomes stuffy. This is an opportunity that has hardly been pursued by anyone in the industry, public or private, but it will gain much more attention in the future.