One guy stormed out of Cafe D at SAP Labs in Palo Alto, empty-handed and half-jesting that he was going to McDonald’s instead. And one woman threw away two slices of bread on her plate and high-tailed it out of there, after realizing there was no cheese to be had at the make-your-own panini station.

But other than that, Melissa Miller, executive chef of the three cafes at the Palo Alto offices of the world’s leading business software provider, couldn’t have been happier with the reaction to Tuesday’s “Low Carbon Diet Day.” The event was held in 400 cafes in 28 states that are operated by Palo Alto’s Bon Appetit Management Company. It’s all part of the company’s initiative to reduce greenhouse gas emissions from food service operations, and to educate its employees and customers about the role food production plays in climate change.

Because SAP’s cafes already feature sustainable seafood entrees, vegan options, and proteins mostly from North America, Miller didn’t have to alter her offerings that much to meet Tuesday’s challenge. Still, it meant no beef and no cheese that day, because cows are said to produce methane gas emissions that are more potent than carbon dioxide at trapping heat against the Earth.

So there was herb-and-yogurt dressing rather than the usual blue cheese one at the salad bar; an Asian pork burger with Thai mayo instead of the regular beef one at the grill station; bowls of chicken pho rather than the typical, traditional beef rendition; marinated tempeh and tofu, and an artichoke frittata standing in for slices of roast beef at the sandwich station;Â and housemade potato chips in self-serve jars instead of individual mass-produced bagged ones.

There also was a striking “Tower of Shame” prominently on display in the cafe — 120 take-out containers (1 per day for six months) piled up to show just how much waste we create simply by getting lunch to-go regularly.

The three cafes serve about 950 people a day for breakfast and lunch. Employees received an email a week ago, telling them that on April 22, Earth Day, the food might be a little different.

“It didn’t bother me that there was no beef or cheese,” said Michael Zahm, vice president of business development for SAP education, who was enjoying grilled chicken. “I like it when they hold special days like this because you can’t help but learn something as you stand in line for your food.  It’s good to make the connections about food, because once you know them, you can make a difference.”