As it has almost every year for more than six decades, the venerable S.S. Badger is again ferrying passengers, cars, and cargo across Lake Michigan this summer. But it's a different ship now.

Passengers shouldn't notice the changes. The beloved horns sound the same, the staterooms remain comfortable enough for a nap during the four-hour crossing, the TV lounges and restaurants are open for business. The large steamship, which is the last coal-burner on the Great Lakes and in the United States, retains its throwback grandeur.

What's missing is some of the ship's pollution. The Badger is sailing this summer season with a $1.2 million, high-tech combustion-control system that reduces the amount of coal it needs for the crossing. It also cuts the accompanying toxic emissions—and, most important, the tons of coal ash the Badger has long dumped into Lake Michigan.

Changes planned for next year are even bigger. The Badger is set to stop dumping any ash in the lake's increasingly clean waters, thanks to systems that will retain the ash on board. It's another $1 million bet by the Badger's owners that they can keep the ship burning coal while staying out of environmentalists' crosshairs.

"We've been an easy target, that's all," says Bob Manglitz, president of Lake Michigan Carferry, the ship's operator. "We really got caught in a political fight."

But with critics contending that the ship is a source of unnecessary pollution that goes beyond the coal ash, that fight may not end anytime soon.

"Filthiest Ship on the Great Lakes"

Until the retention system is installed next winter, the Badger will continue ejecting tons of coal waste every day. The waste amounted in recent years to nearly four tons a day and more than 500 tons a sailing season. The Badger's backers have described the ash as little different from sand, but coal ash contains toxic substances including mercury, arsenic, and lead.

And among the many YouTube videos that show the Badger blowing its horns, docking, and departing, one can also find a video of it spewing ash from its side and into Lake Michigan.

That very visible pollution earned the ship some outspoken opponents, including Dick Durbin, the U.S. Senate's second-ranking leader. The Illinois Democrat last year called the Badger "the filthiest ship on the Great Lakes" and aimed to shut it down, or at least stop its ash dumping. He was joined by a coalition of environmental groups that viewed the Badger as a blatant violation of the Clean Water Act.

"It is time that the Badger stop being allowed to violate the law, and stop polluting Lake Michigan," Howard Learner of the Environmental Law and Policy Center said recently.

The Badger and its defenders embraced the fight as an effort to preserve living history. Congressional Republicans backed a bill that would have shielded the ship from environmental regulations if it were nominated as a National Historic Landmark. The ship already has won a listing on the National Register of Historic Places, among other historic designations.

The legislation died in 2012 and the landmark nomination stalled amid the controversy. With the plan in place to further cut the Badger's pollution, the landmark designation effort was revived in May.

The ship has plenty of support from local residents. At more than 400 feet long, the Badger was built, along with other ferries of its time, by railroad companies that wanted a shortcut across the lake.

The ship launched in 1953 and carried railcars until that traffic dried up in the 1980s, when the Badger went bankrupt. An entrepreneur revived the ship in the 1990s as a summer ferry for passengers and cars.

Built to carry railcars year-round, the Badger is a heavy relic that can sail smoothly on rough waters while carrying as many as 600 passengers and nearly 200 vehicles.

That contrasts with a faster, diesel-powered competitor that also ferries passengers and vehicles. A catamaran, that newer boat doesn't handle the same in rough weather.

"We call that one the 'vomit comet,'" said Juanita Pierman, president of the village council in Pentwater, Michigan.

A summer tourist town, Pentwater depends on the Badger to bring tourists from Wisconsin. It also depends on having fish for those visitors to catch.

"Fishing is great these days because the lake's in wonderful shape," Pierman said. "They're worried about one ferry that runs for the summer months? Come on, let's get real."

A Compromise on Fuel

The fight over the Badger dates to 2008, when the EPA ordered thousands of vessels to obtain a permit for any type of discharge into bodies of water. The Badger got a five-year permit to continue ejecting coal ash, promising to come up with an alternative by the end of 2012.

Environmentalists say the Badger's operators appeared more intent on winning exemptions than on meeting its deadline. "It's puzzling," says the Environmental Law and Policy Center's Learner. "They had a chance to pursue cleaner fuels."

Manglitz said his company studied and rejected coal alternatives, including propane, diesel, and compressed natural gas. Propane is too dangerous for a vessel, he said, while diesel didn't seem immune from environmental concerns.

And the heavy Badger would have needed so much compressed natural gas that the tanks would have been unwieldy.

As the deadline approached, the Badger's owners announced that they wanted time to convert to liquefied natural gas, which Manglitz said would make it the greenest ship on the Great Lakes. The company won a $75,000 Wisconsin grant in 2012 to study the conversion.

But even Manglitz conceded that moving to the liquefied gas was a tricky bet. Suppliers won't build the expensive infrastructure needed to deliver the super-chilled fuel until they have guaranteed buyers, and operators can't make the engine conversions until they have a supply.

"It's a chicken-and-the-egg situation," Manglitz said.

Durbin and environmentalists called the proposal a stalling tactic. When the Badger's five-year permit expired at the end of the 2012 season, they demanded that the ship immediately stop spewing its coal ash into the lake.

EPA officials and the Badger's owners crafted another compromise that would allow the ship to continue operating in 2013 if it reduced its coal use in 2014 and quit dumping ash in 2015.

To reduce the Badger's fuel burning, workers spent the winter installing new digital combustion controls, including more than two miles of wire needed to link sensors, controls, switches, fans, and other new gear to the old steam engines and to panels in the ship's pilot house.

The first few weeks of operation suggested the Badger will meet a goal of reducing fuel consumption by 15 percent. "We'll be tweaking the controls for several months until we get everything working at its best," Manglitz said.

Workers adapted combustion controls from those in use at coal-fired power plants. There is no precedent, though, for an ash-retention system like the one that will be installed on the Badger this coming offseason.

Despite once saying that holding the hot ash was unfeasible, Manglitz said he's confident that the ship will now succeed at retaining the waste, which can be sold for industrial uses or transported to landfills. "But with anything like this, there are a few doubts in the back of your mind," he said. (Related: "Seeking a Safer Future for Electricity's Coal Ash Waste.")

With the new system in place, the Badger could continue operating indefinitely, probably always as a coal-burner. His company won't have the money to later make a fuel conversion, said Manglitz, who likes the coal-fired engines: "Having the old boilers is part of the whole thing."

That means the Badger, whose emissions contain their own toxins, will continue to irritate environmentalists. "No question, we would prefer that the Badger had moved to a cleaner fuel," said Josh Mogerman of the Natural Resources Defense Council, which participated in the campaign to rein in the ship's pollution.

There's a reason the Badger is the last coal-fired ship in the country, he said. "There are simply better ways to move our boats today."