A multifaceted mogul who started the Def Jam music label and the Phat Farm clothing line and developed HBO's Def Comedy Jam, Russell Simmons is more than just a hip-hop impresario, a point emphasized by his latest endeavor. 

The 51-year-old Simmons is serving as the spokesman for America's Greenest Campus, a competition among colleges to reduce their carbon footprint. "Hip hop makes the planet cool. Now hip hop has to save it," Simmons says in the public-service announcement shown here.

Nearly 500 schools have entered the America's Greenest Campus competition, each with an official student organizer responsible for managing campus involvement and promoting carbon-reduction activities, including using the sleep mode on computers, taking mass transportation, and turning off the lights when leaving a dorm room. (With any luck, they're using compact fluorescent lightbulbs.) The competition wraps up on October 5.

Two $5,000 cash prizes will be awarded, one to the school with the most members and one to the school with the largest percentage reduction in greenhouse-gas emissions. The University of Maryland currently tops the leader board; its 2,128 members have reduced carbon dioxide on the College Park campus by 1.17 percent. (Let's hope the frats aren't serving flat beer.) As of September 25, East Tennessee State University leads that category, with its members posting a 22 percent reduction so far.

Simmons has been a vegan for years, something he's connected to the green movement. "The consumption of animals causes more harm to the environment than all the forms of transportation put together," he told CNN last year.

Simmons might want to extend his green efforts to the world of cars. As part of his 2008 divorce settlement with Kimora Lee Simmons, every two years he has to buy or lease a car for his daughters' use, and the vehicle must be valued at a minimum of $60,000 each. Considering that most highly fuel-efficient vehicles cost much less than that, Simmons might be stuck buying the Tesla Roadster, an all-electric sports car that starts at an off-the-chain $109,000.—Daniel DiClerico | e-mail | Twitter | Forums | Facebook

Essential information: Use these expert tips for cutting energy costs and visit our new Energy Saving & Green Living guide for more ways to curb carbon emissions at home.