[crusty old prospector]

PV=znRT. Decrease temperature and you decrease pressure, at least so I have heard.

[thackney]

Methane’s Critical Temperature is -87.4°C

http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=41

At temperatures above a molecule’s critical temperature, liquid phase cannot be achieved.

http://www.chem.purdue.edu/gchelp/gloss/crittemp.html

http://www.chem.purdue.edu/gchelp/liquids/critical.html

You can continue to add pressure and reduce the volume, but you will not form a liquid, just a really dense gas. Then you need to figure a way to deal with the pressure.

LNG is contained in heavily insulated vessels, at atmospheric temperatures. The LNG must be below -259°F at atmospheric pressures to remain liquid.

http://www.lngfacts.org/About-LNG/Overview.asp