Students can now sip Diablo Mocha coffee drinks or dig into white bean and caramelized onion sandwiches — all without leaving their copies of Milton or Machiavelli far behind.

The Bass Library Cafe, which opened Tuesday, offers these and other sustainable snacks — including sandwiches, coffee, tea and salads — to students studying in the new underground library. Formerly Cross Campus Library, the space reopened to hordes of excited students early Friday morning after a $47.8 million renovation.

The cafe, a collaboration between Yale Dining Services, the Yale Sustainable Food Project and the Bass Library, is the University’s first attempt to retail sustainable food outside the residential college dining halls, YSFP director Melina Shannon-DiPietro said.

Dozens of customers crowded into the cafe Tuesday, which officials say is a pilot for more potential sustainable eateries on campus, to sample its initial offerings, but some students interviewed said they thought the prices were too steep — and one complained of her $7 sandwich.

The central location, however, was an irresistible draw.

“Our vision is to create a cafe that acts as a gathering space for the Yale community where students, staff and faculty are nourished by good food,” Shannon-DiPietro said.

She said YSFP staff developed the cafe’s menu with input from students, faculty and library employees and that they aimed to create a cafe that reflected the University’s commitment to environmentally friendly fare.

Students involved in crafting the menu requested that food be served throughout the day in order to offer students more flexibility than do the dining halls. Those in these focus groups, held last year, also asked that the menu be changed regularly because residential college butteries — a popular late-night option for hungry students — often maintain the same menu year-round, Shannon-DiPietro said.

As a result, the cafe plans to alter its menu seasonally and encourage students to provide feedback, she said. A new student and faculty focus group will meet in mid-November, and the library and YSFP hope to create a permanent advisory board for the cafe.

“We want lots of input,” Shannon-DiPietro said. “This is a pilot location, and we want it to work well.”

Yale Dining Services is also employing students at the cafe.

Mellony Lucas, a cafe employee who used to work in the Ezra Stiles College dining hall, said Tuesday afternoon that the cafe’s first day of operations was busy and demanded more work from her than being stationed in a residential college.

“The time goes by much faster because there are so many customers,” she said. “It’s a real rush.”

Emily Ambrose ’10 said while she thinks the menu items are “slightly expensive,” she expected Yale to overprice the food and was not surprised that she had to pay $3 for a cappuccino. But Ambrose said she would come back to the cafe because its central location makes it an attractive option.

Akilah Graham ’11 said she thinks the prices are directly related to the library’s convenient location and to its lack of competition in the immediate vicinity. She said she students will buy the food because the cafe is so close to their study areas.

“You’re not just paying for the food — you’re paying for the convenience,” Graham said.

Allison Jones ’08 said the prices were reasonable and that the menu looked enticing. But her $7 sandwich was disappointing, she said.

“I really wish I could say it was good, but it wasn’t that great,” she said. “I’m hoping that it was just a bad choice.”

The cafe’s convenience may pose a problem to local merchants. Jason Yi, manager of 24-hour Gourmet Heaven on Broadway — which caters to many students who are up late studying — said he thinks the cafe will pose serious competition, but it is too early to determine its long-term impact.

“I’m a little worried because it’s so close to the students,” he said. “I know we will lose business.”

Shannon-DiPietro said Yale is using the cafe as a pilot for what may eventually be a number of sustainable eateries on campus, although YSFP has not developed concrete plans for any future venues.

The cafe is open seven days a week — until 1:30 a.m. Sundays through Thursdays and until 5 p.m. Fridays and Saturdays.