GM showcased a “green” Hummer run by algae at last year’s Los Angeles Auto show: it was really just a concept by someone with neat Photoshop skills.

This year at the 2008 Detroit Auto Show, GM introduced a physical version of an “environmentally friendly” Hummer concept car, the HX. The HX has some elements of a sports car: It’s convertible and has only two doors. It’s lighter than previous Hummer models, with a V-6 engine that can run on E85 ethanol. Because news about the environment can get so dreary, the HX comes without a radio. Instead, it has a USB dock for MP3 players. Though the HX is just a concept design, it does signal GMs intention of equipping future Hummers with E85 FlexFuel engines.

Meanwhile, this year’s 2008 H3 uses old fashioned gasoline and gets 14 mpg on a good day.