It’s one thing to cite the number of watts and BTUs saved by giving sports stadiums an efficiency makeover, but it’s quite another to accurately assess the impact on the environment.

Cracking the code for such metrics was one of the topics at a recent conference — Leadership in Greening the Sports Industry — sponsored jointly by Wharton’s Initiative for Global Environmental Leadership (IGEL) and the Natural Resources Defense Council (NRDC). This article includes information shared at the conference held at Wharton and gathered from additional experts.

The greening of sports movement is still very much under construction, and that means all the pieces aren’t yet in place — but the scaffolding is going up quickly. NRDC’s partnership with MLB, which launched the sports greening movement, initiated the first league effort focused on gathering data about energy, waste and water use from all of the league’s venues.

NRDC then spread that initiative to NBA and the NHL, and it was a principal focus of NRDC’s agenda when it founded the Green Sports Alliance. “From day one, we’ve worked with the teams to understand and collect data, looking at the environmental baseline,” said the Alliance’s Tull. “We’re aggregating the data to better understand the impact of our members in the industry.” (The Alliance is a nonprofit organization with a mission to help sports teams, venues and leagues enhance their environmental performance.)

On a pie chart of major U.S. climate impacts, sports are unlikely to show up. The total annual greenhouse gas emissions from all NHL games, including team travel and league operations, for instance, is estimated at slightly more than 500,000 tons annually, according to NRDC’s Allen Hershkowitz, a senior scientist. That compares with a single coal power plant’s emissions, which can range as high as 23 million tons per year. But energy and waste costs are a major expense for the teams that incur them and making green improvements has been a win-win for sports organizations and fans. The environment is a big beneficiary when sports greening influences fan behavior at home and on the job.

Reports The New York Times, “As large as they are, sports stadiums consume just a sliver of the nation’s energy and produce a fraction of its waste. But they are seen and used by millions of Americans every day, which has helped leagues counter the perception that sports teams are wasteful enterprises and in fact can convey socially responsible messages to fans of all political and economic stripes.”

Sports have a relatively light impact, but, as with other sectors, it is felt in many areas. The United Nations Environment Programme reports, “Building and managing a sport facility and operating an event uses energy and can contribute to air pollution, greenhouse gas emissions and waste generation, as well as to ozone-layer depletion, habitat and biodiversity loss, soil erosion and water pollution.” The impacts — which are common in large public organizations, and hardly limited to sports — include damage to fragile ecosystems, noise and light pollution, energy use and emissions, soil and water pollution and waste generation.

“The 2012 London games were the greenest ever….” –the independent Commission for a Sustainable London

Tricky Metrics

Professional and college sports, both in the U.S. and internationally, have an environmental impact that’s sometimes hard to quantify, because activity both at the venues and getting to and from them needs to be measured, along with impacts related to procurement and other operations. And some of the larger variables, such as travel, are hard for the teams both to measure and to positively influence.

Martin Tull, executive director of the Green Sports Alliance, said that the group’s focus has been “on the best practices side of the equation,” but that’s changing. The Alliance is now working hard to encourage the measurement of the environmental impact of the teams’ achievements, but it’s no simple task. “You quickly run into the fact that the impacts are very different based on the sport, the venues and how many games are played per year,” Tull said. “The Staples Center in Los Angeles may be a very energy-intensive venue, because it’s also one of the busiest venues. We need to be careful about how we measure and report energy intensity, because data points can be taken out of context.”

And, obviously, measurements have to be done on a level playing field, with each team and league evaluated by similar metrics. Britain’s Carbon Trust estimated the impact of a single 2012 championship soccer match (FA Community Shield) at 5,160 tons of carbon dioxide, with transportation (mostly driving to and from the game) responsible for 5,000 tons. The stadium’s energy use, which led to 60 tons of carbon emissions, was down 7%, thanks to efficiency improvements in lighting, heating and other systems.

Big venues can have outsized environmental impacts. During game time, Cowboys Stadium in Dallas is illuminated with 30 million LED light bulbs. But the impact would be far greater if the team wasn’t resolutely pushing environmental initiatives, including pledges to reduce solid waste by 20%, energy by 20% and water consumption by a million gallons annually.

Measuring Progress

Even without sophisticated reports, there’s plenty of evidence that the sports greening movement is helping the environment in small and large ways. Scott Jenkins, vice president of ballpark operations for the Seattle Mariners, said that the team has diverted an average of 500 tons of waste from landfills annually since 2005. In 2012, it was 1,000 tons.

Food prepared at the Mariners’ stadium and not sold goes to social service organizations, and food scraps are composted. Waste paper and cardboard are sold, as are plastic bottles and valuable scrap metal.

The San Diego Padres partnered with a biofuels company, and is providing used cooking oil that is now running local school buses. The benefits include both lower emissions from the buses and avoided disposal impacts from the oil. Again, it’s not a huge win for the planet, but one well worth making. After all, as NRDC’s Hershkowitz reminds us, “There are no giant, single initiatives in business or government that can solve our ecological problems. They’ll only be solved by millions of small advances. Small progress leads to big benefits.”

“Sustainability is trickling into every major sporting event and the sports industry globally.” –Jill Savery

International Impact

Dow’s Teresa Angsten said the company launched a 10-year partnership with the Olympics in 2010. A major benefit, she said, is that the partnership gives the company access to the on-the-ground professionals who build temporary Olympic villages. Since Dow has a portfolio of environmentally preferable energy-efficiency and construction materials — such as cool-roof technology and insulation useful for skating and curling events — the partnership results in events with smaller carbon footprints.

In 2014, Dow will be in Sochi, Russia, for the Winter Olympic Games, and the company is working on both installing energy-efficient windows and improving farming practices. Parts of Dow’s 2012 London Games stadium wrap, made of hundreds of fabric panels, were repurposed for projects benefiting former child soldiers in Uganda, and for use at shaded community areas at the 2016 Summer Games in Brazil.

The 2012 London games were “the greenest ever” held, said the independent Commission for a Sustainable London. Among other benefits, the venue was largely accessed by public transit, which both mitigated one of sports’ biggest impacts and reduced the threatened gridlock. Some 86% of Olympic visitors traveled by rail, according to the post-game sustainability report. And 99% of the 61,000 tons of waste was either recycled or reused.

The America’s Cup Event Authority’s Jill Savery, an Olympian, was on the ground helping embed environmental consciousness into the fans attending the races in San Francisco. She said that although the first environmental efforts for the Olympic Games started as early as 1994, greening really began to take hold during planning for the 2000 games in Sydney, Australia.

Highlights included efforts to save water and energy as well as green building initiatives at athletic venues and the Olympic Village. “And then it moved to another level in Vancouver, and reached even higher in London,” she said, adding that efforts to build sustainability at the FIFA TM World Cup soccer matches began in Germany as early as 2006, with the Green Goal Program.

In 2013, the America’s Cup achieved an 85% event waste diversion rate. Single-serve plastic bottles were banned, and all plates and cutlery were compostable, said Savery, co-editor of the book Sustainability and Sport. “In San Francisco, we trained a team of people to go through the waste — it’s the only way to get high diversion rates,” she said.

At the 2007-2008 FA Cup Final in England, a so-called “Carbon Footyprint” campaign reported major gains, including the gathering of 160,000 pledges on everything from installing energy-efficient light bulbs to taking group buses or walking to games (or even watching events at the pub with friends). By taking free buses, for examples, fans from Wales saved 18.39 tons of CO2 equivalent emissions.

“In Europe, they recognized the issue of climate change long before we did,” said Savery. She cites environmental makeovers at Formula 1 racing and other popular world sports. “Sustainability is trickling into every major sporting event and the sports industry globally,” she added.

The Alliance’s Tull noted his organization hasn’t yet been involved in international events, but it is having discussions about the World Cup and Rio’s Summer Games in 2016. “We have a growing interest in learning from the experiences of these mega-events and from the international teams and venues that have reached out to the Alliance,” he said.