Early in the design phase of what became Mercedes-Benz Stadium, Falcons executives hoped to have a natural-grass playing surface under the retractable roof. But an extensive “sun study” determined that was not an option.

“What we found was … it is impossible to have natural grass in the building because the building is so tall we don’t get enough light on the field to grow the grass,” Bill Johnson, the stadium’s lead architect, said in October 2013.

So an artificial-turf surface was installed and has been used for all football and soccer games played in the stadium since its 2017 opening.

That will have to change in the summer of 2026 if Atlanta succeeds in its bid to host some World Cup games.

Because FIFA, soccer’s global governing body, has a firm requirement that any stadium hosting the 2026 World Cup must have a natural-grass playing surface, Mercedes-Benz Stadium’s artificial turf would have to be temporarily replaced with real grass, which would have to be kept thriving for more than a month.

“Technology and advancements in turf science make us confident that we can meet this challenge to give players the best possible playing conditions in ‘26,” AMB Sports and Entertainment, which operates the stadium, said in a statement to The Atlanta Journal-Constitution this week. “FIFA is already working with all the candidate host cities to ensure a FIFA-led solution can and will be achieved at the highest standard at every stadium while also ensuring it is tested and can sustain the conditions that a month-long competition will present.”

AMBSE, parent company of the Falcons and Atlanta United, isn’t contemplating a permanent conversion to natural grass for Mercedes-Benz Stadium. The company envisions having a grass surface for the World Cup and then returning to artificial turf afterward.

The theory is that, even if real grass wasn’t viable for the stadium on a permanent basis, officials and outside contractors can figure out how to make it work temporarily.

“It’ll be done,” Atlanta Sports Council president Dan Corso, who is overseeing the city’s World Cup bid, told the AJC. “You’ve got first-class people over at the stadium and plenty of resources and people within that field who know how to put together a nice (grass) pitch.”

This isn’t just an Atlanta issue. Eleven of the 23 North American stadiums under consideration as sites for the 2026 World Cup have artificial turf, according to a FIFA bid evaluation report. All 11 have accepted that they’ll have to convert to grass if they’re among the 16 stadiums chosen for games.

The evaluation report also acknowledges the transformation won’t be simple, citing the “research challenge to create a hybrid grass that can be maintained indoors or in other challenging climates” and “risks in ... installation work, different operational procedures, etc.”

The issue came up during a FIFA delegation’s site-inspection visit to Atlanta last week.

“We need to transform the pitch surface from the artificial into an absolute world-class grass-turf pitch which can live in the environment of a closed – or semi-closed if the roof’s open — environment for a long period of time,” Colin Smith, FIFA’s chief tournaments and events officer, said at a press conference between meetings with the Atlanta bid group at Mercedes-Benz Stadium.

“There is lots of technology that exists these days,” Smith added. “We just need to get it right. And we have experts on our side, and we are working with multiple third-party companies and consultants as well. Obviously, we will share all that knowledge with Atlanta in terms of coming up with the best plan forward. That’s not a concern. Technology is there. Capability is there. It just needs the proper planning, care and timeline and to do it properly.”

As for exactly how it would be done, research is underway and no determination made yet.

While a natural-grass surface hasn’t been brought into Mercedes-Benz Stadium in its four-year history, grass temporarily replaced artificial turf on more than a half-dozen occasions at the stadium’s predecessor, the Georgia Dome. The first time was for a Mexico-Venezuela soccer match in 2009. Then, a contractor laid 4-by-8-foot grass sections after Dome personnel installed a thick layer of plastic and two layers of plywood atop the artificial turf. But the grass was in place for only a few days, then was removed and reinstalled for another soccer game a month later.

World Cup standards will be higher and more demanding. FIFA hasn’t said how far in advance of the event it’ll require temporary grass to be in place so that it can take root.

Two NFL teams, the Arizona Cardinals and Las Vegas Raiders, have gone to extraordinary lengths to play on natural grass in retractable-roof and fixed-roof stadiums, respectively. The Cardinals’ rollout grass field is contained in a 40-inch-deep tray that is rolled outside the stadium on 546 steel wheels resting on 13 railroad-like tracks to get sunlight on non-game days. Similarly, the Raiders’ new stadium features a sliding field tray containing a natural-grass playing surface, which is rolled outside, powered by 72 motors, into the sunlight on non-game days.

Temporary conversions for the World Cup surely will be less elaborate, but still challenging and costly.

Among the candidate stadiums faced with converting to natural grass for the event are MetLife Stadium in East Rutherford, N.J., AT&T Stadium in Arlington, Texas, and Gillette Stadium in Foxborough, Mass. Gillette Stadium, home of the NFL’s New England Patriots and MLS’ New England Revolution, has had artificial turf since 2006, but Patriots and Revolution owner Robert Kraft committed during a FIFA visit to Boston last week to bring back real grass for the World Cup.

In the first or second quarter of next year, FIFA plans to select 10 or 11 U.S. cities as 2026 World Cup hosts, along with three cities in Mexico and two or three in Canada. Atlanta is among 17 U.S. cities in the running. While it hasn’t been determined how many matches a single city would host during the 48-team, 80-match event, the Atlanta bid group hopes to land multiple matches spread out over a month, possibly including one of the two semifinals.

Tim Tucker is a sports reporter for The Atlanta Journal-Constitution. He writes about various topics, including the business side of sports.