Fans of the Seattle Kraken, who joined the N.H.L. this season as the league’s 32nd team, had a lot to take in at the club’s first-ever home game last Saturday. There were new players on the ice to cheer, new seats to find and new concession stands to seek.

Yet their biggest discovery seemed to be the 1,800 square-foot green wall that describes the mission of Climate Pledge Arena, the Kraken’s new home, which opened just in time for the game. Hundreds of fans stopped to snap selfies in front of thousands of plants growing in the vertical bedding, which is made from recycled plastic bottles.

Before the game, Jennifer and Shane Pisani were among those who stopped to view the greenery and the screens that showed images of solar panels, wind turbines and a statement, “The World’s First Net Zero Carbon Arena.”

The Pisanis, longtime hockey fans, were happy to have a team in town to cheer. They were also pleased that the Kraken stood for something more than just wins and losses.

“It speaks to what the owners and team want to say to the community,” Shane Pisani said. “I’m looking forward to sitting in a state-of-the-art arena.”

Climate Pledge Arena is indeed state-of-the-art. It includes the latest LED scoreboards, grab-and-go food stands and ticketless technology. But the operators of the $1.2 billion arena are also trying to set a new standard in green building by reducing and offsetting all of the planet-warming emissions that they, their vendors and even their fans produce.

Their mission is expensive, time-consuming and risky, and has never been tried at a sports venue before. Calculating emissions is complex and imprecise, and exposes the arena operators to accusations of “greenwashing” — providing misleading information about the building’s environmental attributes.

Tim Leiweke, the chief executive of the Oak View Group, which owns 51 percent of the building, acknowledged that the return on investment was not obvious, and that much work must be done to confirm that the building meets its targets. But he expects the efforts to pay for themselves over time and the arena to provide a blueprint for others in the industry.

“There’s nothing today that is going to economically reward us for going carbon neutral yet,” Leiweke said. “I believe our fans and sponsors will respect us and the rewards will come, but you’ve got to lead first and take your chances.”

A growing number of sports venues have secured LEED certification from the U.S. Green Building Council, but that designation, which stands for Leadership in Energy and Environmental Design, primarily recognizes eco-friendly infrastructure, not necessarily how a building operates. By trying to become net zero carbon and promising to do so transparently, Climate Pledge Arena could serve as a new model. Commercial buildings accounted for 18 percent of U.S. energy consumption in 2020.

“People over the years have used LEED to guide them, but that only takes you so far,” said Scott Jenkins, a co-founder of the Green Sports Alliance. “We have an urgent need to act and business as usual is not going to cut it. The challenge is, how do we get others to follow?”

Leiweke and the Kraken’s principal owner, David Bonderman, who with his partners owns the other 49 percent of the building, did not start out trying to build the country’s greenest arena. Their biggest challenge was figuring out how to upgrade an arena built for the 1962 World’s Fair with a roof and windows that are landmarks, along with the nearby Space Needle and the monorail to downtown.

After groundbreaking in December 2018, the 44-million-pound steel roof was perched on 72 stilts so the entire arena beneath it could be gutted. Air-conditioning equipment, solar panels and other machinery that might normally be put on the roof were placed elsewhere on the property. A cistern was built to hold 15,000 gallons of rainwater drained from the roof that would then be distributed by electric Zambonis to resurface the ice.

The project has received high marks from environmentalists because it preserves an existing structure in a neighborhood with good access to public transportation.

The renovation got more complicated last spring when Amazon bought the naming rights to the building, spending an estimated $300 million to $400 million for the privilege. But instead of adorning the arena with its logo, as most companies do, Amazon named the building after one of its most ambitious initiatives, the Climate Pledge.

The company unveiled the pledge in 2019, promising to reach zero net carbon emissions by 2040, a decade earlier than the targets set in the 2015 Paris climate agreement. Colgate-Palmolive, Siemens and Unilever are among the 200 companies that have since signed on.

To make sure it walked the walk, Amazon worked with the builders to cut the arena’s emissions, mirroring the efforts in its own offices and facilities. “We’re trying to draw attention to the climate crisis, and we’re trying to draw attention to the solutions that exist,” said Kara Hurst, Amazon’s vice president of worldwide sustainability.

The new mandate upended the project. Leiweke hired Jason McLennan, an architect and environmentalist who founded the International Living Future Institute, which created a certification program for sustainable buildings that goes well beyond LEED requirements.

To meet those goals, the building couldn’t use fossil fuels. Orders for dehumidifiers, pizza ovens and even the machines that dry players’ gloves had to be canceled because they were powered by natural gas. Electric replacements had to be found.

Next, the electricity that powers the building had to come from renewable sources. Solar panels were placed on an atrium at the arena, at a nearby parking lot and at the team’s practice facility north of Seattle. More electricity was purchased from a wind farm in Eastern Washington.

The arena is trying to divert 97 percent of its waste from landfills by composting, recycling and using biodegradable cutlery; single-use plastics will be eliminated by 2024. On opening night, fans were served beer in recyclable aluminum cups. Leiweke’s team is working with Pepsi and other companies to eliminate plastic wrapping and other packaging.

“We haven’t had any significant pushback from suppliers, but check back with me in a year,” said Rob Johnson, the head of sustainability for the Kraken.

The biggest challenge is calculating the emissions produced at the building, as well as those produced by fans who travel to the arena and every vendor that delivers products. Surveys will help determine whether fans arrive in gas-powered or electric cars, or take buses, light rail, the monorail and other public transportation — which they can ride for free by showing their Kraken or concert tickets. Their carbon emissions will be added to the building’s tally. So will the emissions from charter flights that the Kraken and visiting teams take to and from Seattle.

Tracking the emissions of vendors is more difficult because their carbon footprint varies widely. Molly De Mers, an executive chef for Delaware North, a hospitality company that runs food service operations at the building, said three-quarters of the food used at the arena comes from farms and ranches within a 300-mile radius of Seattle.

When sustainability is weighed against profit and loss, “that’s where it gets tricky,” De Mers said. “Because obviously costs rise when you start incorporating that.”

The local buying means avoiding foods like avocados from Mexico. De Mers also chooses foods that can be prepared in multiple ways. Watermelons are served as vegan sashimi, and their rinds are pickled and used in salads. Carrot tops are turned into gremolata, a condiment. Plant-based burgers, which have a lower environmental footprint than beef burgers, are sold on the main concourse.

The arena’s emissions will be tallied at the end of each year, and Amazon and the Oak View Group will offset any carbon produced by buying credits in environmental restoration programs. The data will be made public to help hold the building operators accountable, McLennan said.

“No one’s ever done that, not even in any of the deepest green buildings,” he said.

For now, the “Net Zero Carbon” declaration on the green wall is more aspirational than real because it will take at least a year for auditors to tally the emissions. Even then, the building will be “functionally zero,” McLennan said, because “true zero is nearly impossible.”

This linguistic sleight of hand alarms some longtime environmentalists, who worry that if the building’s ambitious goals are not met, critics may argue that the project amounts to marketing without substance.

“Claiming superlative accomplishments like ‘carbon neutral’ or ‘net zero’ without specifying what scope of impact is being referred to or, much worse, claiming such a lofty accomplishment when it is not actually achieved, is greenwashing,” said Allen Hershkowitz, who advises the N.H.L. and other teams and leagues on environmental matters. “It breeds cynicism instead of inspiration.”

McLennan acknowledged that the building would be certified only after its first year of operation. But he is confident the goal will be met.

“This is not greenwashing,” he said. “Everyone needs to look in the mirror and say, ‘We’ve all been part of the problem,’ and we need to say, ‘OK, fair enough, but what are we doing now and what do we do going forward?’ That’s how I would respond to that.”