“Demandite” is the word used by mineral economists to describe the materials that must be provided-- usually by mining-- to meet the needs of civilization. In the usual terrestrial setting, air and water are assumed to be freely available, and fossil fuel (natural gas, crude oil, and coal) is considered a necessity. In space, where dependence on solar energy is the norm, and where air and water must be “mined”, the numbers are different. The proportions of mineral needs, however, are otherwise generally similar. You can then ask how much of each material (iron, carbon, nitrogen, aluminum, copper, oxygen, water, nitrogen, etc.) is needed to be in circulation to support one person, depending on “renewable” (inexhaustible) solar energy to drive industry, agriculture, and recycling. We can then compare those requirements to the natural resources available on bodies in nearby space, and calculate how many people could be supported at each of those locations.
The proportions of these necessary materials (the relative abundances of water and iron, for example) are very different on the Moon, Mars, and nearby asteroids. The Moon, for example, is severely deficient in all volatile elements, including carbon, nitrogen, hydrogen, and chlorine, Mars, with its tenuous atmosphere and widespread ice deposits, fares better. But best by far is the match between the composition of near-Earth asteroids (NEAs) and “space-based demandite”. The 1000 or so kilometer-sized near-Earth asteroids contain enough of every essential element to support a population of 10 billion people from now until the Sun dies of old age. The NEAs, however, are a renewable resource: in nature, the rate at which NEAs are lost by collision with planets and ejection from the Solar System is compensated by recruitment of fresh asteroids kicked into near-Earth space by Jupiter’s gravitational interactions.
But what about the main Asteroid Belt? The answer is startling: the Belt contains one million times as much mass as the entire NEA population. Again depending on the Sun for power, the Belt could support a population of 10 million billion people-- a million times the ultimate carrying capacity of Earth. With that many people, wouldn’t we be running out of solar power? Not really-- even under these extreme assumptions, we would require less than one millionth of the Sun’s output energy.
The non-renewable resources available to Earth-bound humanity are finite. The resources available to a space-faring humanity are effectively infinite.