Part 2 of 2 Parts (Please read Part 1 first)
The lunar regolith is composed of about forty five percent oxygen. However, that oxygen is tightly bound into the minerals mentioned above. In order to break those bonds, a great deal of energy must be applied.
There is a chemical process called electrolysis. On Earth, this process is commonly used in manufacturing. One example is the production of aluminum. An electric current is passed through a liquid form of aluminum oxide via electrodes to separate the aluminum from the oxygen. During this process, a great deal of oxygen is released as a byproduct. On the Moon, use of electrolysis would produce breathable oxygen as the main product. Aluminum or any other metal would be a potentially useful byproduct.
It is a fairly simple process, but it does require a great deal of energy. In order to be sustainable, it would need to rely on solar energy or other energy sources available on the Moon.
Extracting oxygen from the lunar regolith would also require a great deal industrial equipment. First, solid metal oxides would have to be converted into liquid form. This could be accomplished by applying heat or heat combined with solvents or electrolytes. The technology to do this exists on Earth. However, moving such equipment to the Moon and generating the energy to operate it would be a serious challenge.
Earlier this year, Belgium-based startup Space Applications Services announced that it was constructing three experimental reactors to improve the process of generating oxygen with electrolysis. They intend to send the technology to the Moon by 2025 as part of the European Space Agency’s (ISRU) mission.
That said, what is the estimated amount of oxygen that could be extracted from the lunar regolith? If the oxygen locked up in the deeper hard rock on the Moon is disregarded and just the oxygen in the regolith considered, estimates can be made.
Each cubic meter of lunar regolith contains one and four tenths’ tons of minerals on average. This includes about fourteen hundred pounds of oxygen. According to NASA, humans need to breathe about twenty-eight ounces of oxygen a day to survive. So, fourteen hundred pounds of oxygen would keep a human being alive for about two years.
The average depth of the regolith on the Moon is about eleven feet. It should be possible to extract oxygen from all of it. The top eleven feet of the Moon’s surface could provide enough oxygen to support all eight billion people currently living on Earth for around one hundred thousand years. Of course, all this would also depend on how efficient our extraction system was.
It is unlikely that there would ever be even a tiny fraction of eight billion people living on the Moon. However, it is good to know that however many people do inhabit the Moon, oxygen will not be a problem. There should also be plenty of water available from ice deposits in craters or water locked up in glass spherules in the lunar regolith.