I mean, to answer your methane question - after our local landfill was filled up, it was covered with foil, then several layers of soil and finally grass - it's a public park nowadays. The methane is collected at the highest point of the hill that was the landfill, I imagine the layer of foil forces it to go up to the single outpipe at the top.
Yes, there really are several successful companies who specialise in landfill gas recovery, it's profitable and practical. But I don't think it's neccessarily a reason to continue with landfill in itself.
