Kevin Douglas, a little known, but hugely successful, investor, is throwing even more money behind Westport Innovations (Nasdaq: WPRT), a Foolish favorite and one of Douglas's most recent positions. In the last three months he's put another $35 million on the line, for a grand total of $54 million in 2012. 

As the single largest holder of Westport stock, Mr. Douglas has a lot riding on its success. 

There are other ways to ride the natural gas wave besides Westport. Clean Energy Fuels is another popular choice, and you can read more about why to buy and sell the company today in our brand new research report. If you're looking for something else, make sure you don't miss The One Energy Stock You Must Own Before 2014

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.