SANTA CLARA, Calif. -- On college campuses, at the offices of some of Silicon Valley's largest high-tech firms and in the confines of San Francisco's AT&T Park, a new diet was rolled out Tuesday but its aim was not just the waistline. It also targeted your carbon footprint.

Designed by Palo Alto-based commercial catering giant Bon Appetit Management Co., the new menu included several items designed with ingredients that will allow the diner to lower their carbon impact on the environment.

Instead of beef burgers, portabella burgers were offered. Chicken -- the production of which has a smaller carbon impact than beef -- was used in many of the menu items in the 400 college and corporate cafés Bon Appetite runs nationwide. And talk about your greenhouse greens.

Among those cafes were food venues at Santa Clara University, Yahoo and eBay.

Lori Flashner, general manager of Bon Appetite's operations at Santa Clara University, said global warming was on everyone's mind now days.

"To me what it means is very simple, it's just how food relates to climate change," she said. "It's an opportunity for us to find ways within our cafes to give back to the environment and our communities."

Helene Yorke, who is heading the Low Carbon Diet initiative at the Northern California firm, said the meal strategy was designed to reduce her company's greenhouse gas emissions by 25 percent over the next five years from the 80 million meals it serves annually.

"The food system is responsible for one third of global greenhouse gas emissions," she said. "That has to do with a variety of things…transportation…whether food comes in by truck or train or ship or plane…It’s also how livestock is raised and the byproducts of livestock production."

The company sought to educate its diners on how food choices lead to greenhouse emissions whether it be from the trucks that transport the products to market to the kinds of gases created by rotting food that is thrown away.

In its cafeterias, Bon Appetit put up posters heralding their new efforts on Earth Day. The posters read: "You've changed your light bulbs, now change your lunch."

At Redlands College, students were given low carbon choices on Tuesday.

"For the most part here today, it's local and it's fresh," said John Rose, the company's executive chef at Redlands. "That's what we're trying to do -- show people you can get something nice and it doesn't have to come from all over the world."

Among the tips the company was suggesting to its diners were -- to reduce the amount of beef and cheese you eat, drink tap water instead of bottled water and buy fruits and vegetables grown locally to cut down on truck emissions.