Many investors were wondering which area would buy into the idea of natural-gas-powered vehicles first: the infrastructure companies or the user base. Well, Clean Energy Fuels (NASDAQ:CLNE) put that debate to rest in 2012. Building out its infrastructure became a key initiative in the last year, and it finally appears to be paying off with a growing customer base. Some of the biggest company names in the world are seeking to increase their exposure to this technology in 2013 after slowly entering the market in 2012.

To find out some of the well-known companies using this technology, check out the video below.