A good idea, but in practice the usual household rubbish which cant be recycled, cimpresses down but springs back, so it is difficult to get 3x volume in the bag. If you do manage it, the weight is more than the bag can stand, and tears around the top. It is also difficult to anchor the top of the bag in place, it tends to detach from the frame it is supposed to be fixed to.
All in all, a waste of quite a lot of money.