Life support in space, and submarines, currently relies on canned air or oxygen and chemical filters to remove carbon-dioxide and other things from the air. This is the best way of doing so, when air tanks can easily be refilled from an outside source, and filters replaced with new ones when full. Longer duration trips away from a source of bottled oxygen will require finding water and making it there or returning before you have exhausted your limited supply and filters that can be cleaned out.
Much of the mass of the initial manned mission to Mars will be either, liquid oxygen, or water to be turned into oxygen, to provide three years’ worth of breathing. This could go as high as one ton of water per person just to insure breathing for those three years. This is in addition to the water for other uses. A better system needs to be set up as soon as possible on Mars so only a three-month supply instead of a three-year supply need be carried on the successive missions.
There have been suggestions of algae tanks for oxygen carbon-dioxide processing on Mars. These are very promising and in all likelihood will carry some of the load. Yet like all monocultures, they are unstable unless perfectly maintain. If just processing carbon-dioxide into oxygen was involved these might still make sense. But carbon-dioxide isn’t the only waste product that needs to be dealt with. Urine and feces must also. At present feces is discarded and the urine is filtered and the water is returned to the tanks. Yet there is a way to process these back into useful biomass, the bio regenerative life support system.
In simple terms, the bioregenerative life support system is growing plants for food and processing the carbon-dioxide and other products at the same time. Russia, China, and the United States have all tested different versions of this. All found it much more complex than just planting some crops. None of them worked well and only processed a fraction of the waste being generated.
Thanks to commercial vertical farmers we have far better data to design such systems now. A large number of them use tailored LEDs. These result in growth rates twice to ten times the growth rates the early experiments got. Commercial systems need to pump in large quantities of carbon-dioxide to do so they grow so fast.
Several of these vertical farms are using aquaponics instead of straight hydroponics. The use of fish waste to provide all the nutrients has much going for it. The growth rates, while not as high as a chemistry tailored to specific plants are still several times faster than earlier methods. The systems are more robust and handle multiple plant species at once much better. Then there is the fact that these produce fish, an added bonus. This makes it worth the extra work and equipment needed.
The way certain of the aquaponics systems handle breaking down the fish waste for use gives an insight into how to do the same with human waste and how much growing volume you are going to need to handle it. As it is better not to use the system for human waste for human food production, these rooms will grow industrial plants and crops intended as feeds for fish and any other animals the colonists may want to raise such as soya.
In the rooms processing human waste, you will also have a significant amount of selected insects. These will serve many different functions here including providing a protein source to be added to the fish and animal feed to increase their nutritional value. They also help in processing plant waste, keeping down harmful fungus and mold, and improving the ecology of the building they are in.
In addition, a well-designed bioregenerative life support system will contain large planted aquariums in every room. These well-lit tanks with room air bubbling through them are important for keeping the air oxygenated, and as part of the filtration system. The aquatic plants and algae in a well-planted aquarium will carry part of the load of keeping that air fresh. Spores, fungus, molds, and such that are a part of any enclosed system will be trapped when passing through these tanks. These will be a key part of such a system.
A bioregenerative life support system isn’t a single system. It is a collection of several interdependent systems designed to mimic the ecology of Earth that has kept the atmosphere breathable for hundreds of millions of years. Set up and maintain well it will keep people on Mars alive and health.
Eptle 