BOSTON—State officials announced an unprecedented agreement with Harvard yesterday that will restrict the amount of greenhouse gas that can be produced from buildings on the University’s planned 215-acre campus in Allston.

The measures commit the University to keeping greenhouse gas emissions in Allston’s new 589,000-square foot science center at 50 percent below national standards, while other projects within the next 20 years will have to remain below 30 percent of national standards.

The agreement—the first of its kind in the nation—coincides with a revision of the state’s policy on greenhouse gas emissions, which requires developers to assess the risk of gas production before beginning construction. Unlike the Harvard agreement, however, the state’s policy does not specify numeric targets.

Christopher M. Gordon, the chief operating officer of Harvard’s Allston project, said in a telephone interview that the pact reinforces Harvard’s commitment to creating a “very sustainable campus.” He added that the Allston team had considered windmills, winter gardens, and heat extraction from sewers as some strategies to meet the goal.

“Harvard’s Allston campus ultimately will be the university’s greatest expression of environmental sustainability,” Gordon said in a written statement.

At the same time, Massachusetts Secretary of Energy and Environmental Affairs Ian A. Bowles approved a special review procedure for the University’s expansion.

Typically, developers must explain potential environmental impact before the state grants approval for projects. Under the new procedure, however, Harvard will not have to immediately present a comprehensive report on the Allston project’s total environmental impact. Instead, the University will be allowed to detail the potential impact of each individual project over the next 20 years.

“We’ve set up a process that is appropriate for a large development project with many facets and parts, when it’s often not possible to determine the environmental impact at the beginning,” said Robert Keough, spokesman for the Massachusetts Executive Office of Energy and Environmental Affairs.

Keough said that the special procedure, which has also been used for the redevelopment of the Fort Debbins Army base and the South Weymouth Naval airbase, will not mean a speedier review process for Harvard.

“Typically, in the special review procedure there are voluminous filings so there’s certainly no lack of scrutiny,” Keough said in a phone interview last night.

In addition, the agreement reached yesterday requires Harvard to create a committee that includes Allston residents and several state-appointed members to examine the environmental impact of the University’s plans.

Residents and state politicians have criticized Harvard in the past for doling out information about the expansion in a piecemeal manner, something University officials say is an inevitable component of long-term development.

Though other universities expanding into Allston have not yet made similar commitments, Bowles said in a statement that he hoped Harvard’s voluntary commitment to reducing greenhouse gases would have broader influence.

“The challenge of curbing emissions is global and progress is too often very slow, but today, we take an important step forward. This is a first,” he said. “Harvard’s Allston project will now be watched carefully around the country.”

Harvard could break ground on the science complex as soon as this fall, pending final approval from Boston officials next month.

—Natalie I. Sherman contributed to the reporting of this story.

—Staff writer Laura A. Moore can be reached at lamoore@fas.harvard.edu.