>They could therefore end up in landfills, causing a longer-term environmental problem than if we simply recycled the material we already have in these large deposits of everything that humanity has created. 

All in all I am in favour of mining asteroids, I think the benefits outweigh the negitives, if done properly. The moon i find less preferable (similar to mining on the earth) because it has a direct link to our planets habitat.

The article answered my main concern with the prospect of mining in space, the recent drive in renewables and sustainability I think are really important, if it becomes cheaper to just consume and mine from space then it cod shift the general world mentality away from sustainability.

So something the article didn't answer for me is how will this theoretically be done?

I would assume we will not be firing people into space to mine and then back and forth, because the cost to sent people into space and back constantly will suck for the environment.

I would assume we'd developing a self maintaining robotic fleet that can mine, package and fire the goods back to earth. I don't think we are there yet, but it's an exciting (and a little scary) prospect.