We can't while supporting the current population. Food takes a lot of land and effcient high production needs each region to specialize. Disasters like drought require long distance transport to handle
I think we could with solar panels, LEDs, hydroponics and sewage reclamation. It wouldn't take so much land if all this was in tall buildings or multiple levels underground. Any methane involved could be put into biofuels for vehicles or lighting/temperature control of the hydroponics.
