A ring of antimatter, more specifically antiprotons, has been recently discovered around the Earth. Since antiprotons are charged sub-atomic particles, they are confined by the planet's magnetic field lines.
Unlike conventional rockets, launch loops can have many launches per hour, independent of weather, and are not inherently polluting. Rockets create pollution such as nitrates in their exhausts due to high exhaust temperature, and can also create greenhouse gases depending on propellant choices. Launch loops require power in the form of electricity and as such it can be clean.
The space elevator is a gigantic concept and as such it has many safety issues that would have to be resolved before construction begins. A space elevator would present a navigational hazard, both to aircraft and spacecraft.