Consider a scenario where there is an over-populated solar system (not necessarily our solar system). Several other rocky planets and moons in this solar system are inhabited by the same humanoid race, and every planet's population is reaching its Malthusian limit. It's not too hard getting things into space (via a space elevator, or something like it). Travel between planets is also relatively easy, but travel outside of the system is not feasible. Attempts have been made, but nothing successful has come of it. Limits on reproduction are enforced, but population culling would be considered unethical and war is uncommon.
Besides over-crowding, every planet in this system has had a serious waste management problem. In order to combat this, for the past 50-ish Earth years, each planet has been shipping its garbage into space. Let's assume that this "cosmic dump" lies outside the effective reach of any nearby gravity well, and the trash itself isn't really moving through space at all.
Leaders and committees of the various planets have come up with an idea to deal with the rubbish that is filling up space and perhaps help relieve the population crisis.
The idea is this: take all the garbage that is floating around space and bring it to a massive asteroid. Using the asteroid as a core, they'll dump all the garbage onto the surface, making it somewhat larger.
For some rough Fermi estimations, let's assume we have:
- 50 earth years worth of trash
- 10 billion people on each planet
- 10 inhabitated planets
- Each person produces 2 tons of waste per year
This comes out to be about 10 trillion short tons, or 9.07185x10^15 kg of material. The largest asteroid in our solar system, Ceres, is 946x10^18 kg. Using that as a figure, and adding the waste our trash planet would be about 9.4600907x10^20 kg. Let's also assume that the contents of the waste are distributed as per http://www.epa.gov/epawaste/nonhaz/municipal/.
I'm guessing gravity would be pretty low on trash planet. Feel free to play with the numbers a bit to make it larger, if necessary. Also, please don't focus on the holes in my scenario - it can change...my main question is, could trash planet support a population? What if we added nuclear waste, let's say 1 billion kg of it? How would that change habitability? If trash planet is habitable, would the population it could support even really help reduce the strain on the other planets?