At the Cleveland Indians home opener on April 10 crowds can expect to hear super fan John Adams pound away on a bass drum in left center field as he has in virtually every home game since 1973. Over by the first base side of the field—and commanding a bit less attention—game- goers may also notice another distinguishing feature at Cleveland's Progressive Field: an upper deck solar panel array. The Indians were the first American League team to install an alt-energy power source in 2007, making it a member of the growing number of ball clubs whose stadiums are going green.

"We view ourselves as a civic leader, so it's our duty not just to think and act green, but to try to influence fans and the community, as well," says Curtis Danburg, a spokesperson for the team. The franchise put up $100,000 toward the $180,000 panels, with two grants covering the rest. Danburg says the panels generate 8.4 kilowatts, or "enough to energize the 400 televisions we have in the ballpark."

Many Major League Baseball (MLB) teams echo these sentiments, having taken similar action to "green up" their sport. In a partnership announced last year, the commissioner's office joined with the Natural Resources Defense Council (NRDC), an environmental advocacy group based in New York City, to spearhead the Team Greening Program. The initiative helps teams figure out ways to do their part in protecting the environment and staving off climate change.

"This effort is really changing baseball for the better," says Allen Hershkowitz, senior scientist and coordinator of the sports greening project at the NRDC. "Baseball isn't green yet, but it's in the process of greening."

The process has unfolded in much the way the game is played, with the MLB's franchises trying to best one another in scoring energy efficiency accolades. "Everything reduces to a competition in our game," says John McHale, executive vice president of communications for the Office of the Commissioner of Baseball, only half kidding. "And when you see something this positive come out of that, it's great."

He says that pro baseball has not yet collectively calculated its carbon footprint, but some individual teams have attempted to keep tabs on their contribution to global warming. The Philadelphia Phillies, for example, purchased about $250,000 worth of renewable energy credits to offset their Citizens Bank Park's utility power use for all of 2008, says team spokesperson Brian Mahoney. These credits—intended to pay for carbon-neutral electricity production from wind turbines and biomass burning—will also be bought to offset stadium energy needs for 2009, Mahoney says.

In a win–win, though, many teams have already financially benefited from reducing energy use and expanding recycling. The Seattle Mariners, for example, saved almost half a million dollars by cutting natural gas and electricity usage at Safeco Field by about 36 and 18 percent, respectively, the past two seasons, says team spokesperson Rebecca Hale. The organization also recycled 342 tons of plastic, glass and cardboard last year, saving $60,000 in waste disposal costs.

Teams have taken other steps to change or reduce their waste: Cleveland, for instance, introduced biodegradable cups made of cornstarch last year and the Mariners have recycled food waste for use as composting since 2007. Other eco-conscious steps include bicycle valet service at some stadiums for fans on game days and using biodiesel—instead of fossil fuels—in field maintenance equipment.

The green zeitgeist has extended beyond the activities inside ballparks to stadium design over the past few years. A prime example is the Washington Nationals's new home in southeast D.C. that opened last year, earning baseball's first leadership in energy and environmental design (LEED) certification. Developed by the U.S. Green Building Council (USGBC), the LEED program's auditors awarded green points based on the Nationals' high-efficiency lighting and air-cooling that saves millions of gallons of water a season, among other conservation metrics.

Nationals Park planners had the environment in mind well before pouring concrete: They chose to build on a reclaimed brownfield site along the Anacostia River south of the Capitol that was once contaminated by chemicals. To prevent stadium-generated pollutants from leaking into the river, workers buried five stories of sand underground to form a state-of-the-art filtering system as well.

On deck for LEED certification include the Minnesota Twins's ballpark opening next year in Minneapolis and the Florida Marlins's new field in Miami (the team will become the Miami Marlins in 2012 when the stadium opens), with the MLB ponying up $1 million toward the Marlins’s facility to ensure greenness, says McHale. The San Francisco Giants, meanwhile, have been upgrading in an attempt to make nine-year old AT&T Field the first environmentally retrofit stadium to get LEED accreditation. (The Giants installed the league's first solar panels in April 2007 a few months before the Indians followed suit.)

Brand-new stadiums opening their gates this season also exhibit some of the latest in green stadium technology and conservation. The lavatories at the New York Mets's newly built Citi Field in Queens, N.Y., for example, feature metered hands-free faucets and waterless urinals. "It's crazy to use drinking water to flush urine," says Hershkowitz.

Across town in the Bronx, the Yankees's new stadium will employ reflectors to amplify stadium light output, using 300 watts per lamp less than standard field-illuminating lights. The Yankees say these advanced lighting systems will save over 100 tons of carbon dioxide emissions per night game—the "ballpark" equivalent, if you will, of planting a tree for every pitch that's expected to be thrown during a home game for the 2009 season.

Even the nation's oldest MLB stadium still in use—Fenway Park, home of the Boston Red Sox, the Yanks's biggest rivals—is getting in on the greening (puns about its legendary "Green Monster" wall in left field aside). Some 28 newly installed solar panels on the fifth floor's slanted roof offset 37 percent of the natural gas burned to heat the stadium's water supply, says Katie Haas, a team spokesperson. The park also sports 11 BigBelly solar-powered trash compacters on the premises.

Despite this deep lineup of energy conservation measures, many methods for greening up the national pastime remain. The NRDC's Hershkowitz emphasizes that all teams need to start using recycled paper, for instance, for everything from game programs to toilet paper.

Transportation looms large, as well. "At the end of the day, the biggest contribution to baseball's carbon footprint is people driving to the game," says Michel Gelobter, the founder and CEO of Cooler, an Oakland, Calif.–based software firm that tracks carbon footprints and reduction methods.

He believes future stadium site selections should encourage fans to use mass transit system access instead of clearing acres of land for parking lots. A good example of this, Gelobter says: The Number "7" subway that shuttles fans between Midtown Manhattan and Queens to see the New York Mets play, as well as the public transport available in Atlanta to carry people to the Braves's stadium there.

With a bigger rollout of renewable energy sources such as solar and wind (Cleveland is looking into adding turbines), Gelobter envisions a time when stadiums could perhaps generate more power than they consume. "The ability for stadiums to become smarter with their electricity use and even make power is much better than their being an energy sink," he says. Hershkowitz says his organization estimates that about 70 percent of energy at MLB parks comes from fossil fuels, and less than 1 percent from renewables like solar and wind.

Hershkowitz and others hope that baseball and other professional sports' green moves will serve as a model for others. "The biggest payoff from this green effort may a cultural shift," he says.

Brendan Owens, the vice president of LEED technical development for the USGBC, agrees. "If team organizations can capitalize on the educational opportunity they have as a result of a million or two million people coming through their gates every year, that can have a significant ripple effect throughout the community," he says

Gelobter believes that the advent of greater greening brought about through sport bodes well in the face of increasingly dire climate change assessments. "I think it's good to align artistic and athletic expression," he says, "with the long-term health of the planet."