Inside Sheryl Crow's 'Stop Global Warming' Tour

"There's no sleeping in the nude on the tour bus!" Crow, 45, joked to PEOPLE on the first day of her "Stop Global Warming College Tour," which kicked off Monday at Southern Methodist University in Dallas.

Crow and An Inconvenient Truth producer Laurie David are touring 11 campuses to inform college students about the climate crisis and how they can help stop it. (They also have a documentary team with them filming the tour.)

"Laurie and I just met in November, and now we're sleeping together," Crow said with a laugh. "On a bus in separate bunks!"

On a more serious note, Crow told PEOPLE: "When I learned how serious global warming is, I wanted to do something to help. So when [Laurie] and I were talking about what we could do, well, my answer to everything is to get on the bus and take it to the people, in true troubadour fashion."

And what is Crow doing to be eco-friendly? "I try to wash my clothes in cold water as much as I can," she said. "I turn off lights in rooms that I'm not using. I drive a hybrid. I'm getting solar panels for my house." Joking with her guitarist, Tim Smith, she added, "To save water, I'm only going to shower once a week, like I did when I was a kid – on Saturdays."

Also, Crow's tour bus is running on eco-friendly biodiesel fuel. "We're in a bus powered by vegetable oil, so we're craving French fries the whole tour," she said.

She began the tour by rocking SMU's packed McFarlin Auditorium, where she also urged students to join the virtual march at Stopglobalwarming.org. "At the end of our journey, we hope to be taking a million marchers with us to Congress to let them know that we demand a change," she told audience members, who were each given an energy-efficient Philips compact fluorescent light bulb.

At a Q&A session after the concert, students asked what they could do to help. Among the tips from Crow and David: Reuse plastic bags, inflate your tires and don't idle your car.

But one hunky student had more pressing matters on his mind: "Are you going to be in Dallas long?" he asked. Laughing, Crow told her longtime guitarist, Tim Smith: "Can you get his number? I don't have any homework to do!"

As the bus pulled away from the SMU campus and headed to Texas A&M in College Station, the group sat around talking about the day's events and munching on Doritos and pizza. "You would think that being on tour with a rock star that there would be a lot of drinking," David said. "Instead there's a lot of eating."