Well, because of the fact that the lanterns can come from whatever species there is in the whole universe it is quite possible that they are able to lift 100 tons by their hands. Of course not the ones from earth, but taken an "average power" for all the lanterns it is possible.
@dondave: They can use their hands or build a construct to do it as long as their powered by their rings. It makes no difference.
@AverageKoala: I don't think Kilowog has ever been shown to be a 100 tonner without the ring. The vine wiki has him at 75+ tons without his ring, but even that I wouldn't buy into without seeing scans.