Disclosed are methods and systems for vaporization of liquefied natural gas (LNG) that employ a condensing gas stream to adjust the gross heating value (GHV) of the LNG such that, upon vaporization, a natural gas product is obtained that meets pipeline or other commercial specifications. The condensing gas can be air, nitrogen, or in embodiments, NGLs such as ethane, propane, or butane, or other combustible hydrocarbon such as dimethyl ether (DME) depending on a desired change in GHV. In some embodiments, the methods and systems employ an integrated air separation plant for generation of nitrogen used as a condensing gas, wherein a cool stream of a heat transfer medium, such as water, ethylene glycol, other common heat transfer fluids, or mixtures thereof, obtained by heat transfer during vaporization of the LNG is used to pre-cool an air feed to the air separation plant, or to cool other process streams associated therewith.