PARK CITY — The greener side of the Sundance Film Festival emerged publicly this year when Robert Redford sipped from a reusable green Nalgene bottle during a press conference.

It unofficially kicked off an effort this year to increasingly lighten the annual festival's carbon footprint on Mother Earth.

"From what I've seen, it looks like a big effort is being made," said Annabelle Gurwitch, host of "Wa$ted" on Discovery's Planet Green TV. "Redford has always been striving to make the festival green — it's not like it's anything new for Sundance to want to be green."

If Gurwitch's name or image looks familiar, it may be because she's been on just about every talk show to talk about her book "Fired" and the documentary that followed — she wrote about being fired by Woody Allen. She hosts the TBS show "Dinner and a Movie." Her columns and commentaries appear in or on major newspapers, CNN and NPR.

On Gurwitch's "Wa$ted" program, the warm but spunky Los Angeles-based mother audits homes to help them run more eco-friendly. The author, actor and activist took to Park City's Main Street Saturday to deepen the festival's already "green" hue by trading unsuspecting people their disposable bottles for the now ubiquitous light green reusable bottle.

"Sure, I would love to have one," said Teresa Calkins, who was pushing her daughters down Main Street.

A Boston woman named Carrie Drinkwater (yep, that's her real last name) also traded bottles with Gurwitch, who was quick to remind people about the potential of chemicals leeching into the water they were drinking from the disposable plastic bottles.

The bottle swaps were captured on video in conjunction with a project by festival sponsor Timberland and its offshoot enviro group Earthkeepers.

Timberland puts so-called nutrition labels, measuring eco friendliness, on boxes for all of its products and it also has a solar-powered distribution center in California. The company placed recycle bins throughout Park City for the festival. Gurwitch was the right fit for Timberland to spread its own green message on a national stage.

"We wanted to partner with someone with shared values," said Margaret Morey-Reuner, a Timberland marketing manager. "There's a very authentic attribute that Annabelle brings to everything."

Gurwitch and her crew invaded a shop on Main Street and changed out already energy efficient light bulbs with even more earth-friendly CFL bulbs (those twisty shaped bulbs you probably haven't installed in your own home yet).

"It's one action at a time and it's a community activity," Gurwitch said about going green.