Billionaire news mogul and New York City Mayor Michael Bloomberg (I) announced today that he will donate $50 million to the Sierra Club over the next several years, helping the group expand a campaign to wean the country off coal.

Pollution from coal-fired power plants is a "self-inflicted public health risk," Bloomberg said today, calling for swift action addressing climate change and a shift to cleaner sources of energy. He announced the gift aboard a boat on the Potomac River, with a 62-year-old coal plant behind him and the U.S. Capitol visible in the distance through the summer haze.

"Even though coal-burning power plants may seem to have a cheap price tag, the real price tag is hidden: hidden in medical bills we have to pay and environmental cleanups that we have to pay for," he said.

New York City Mayor Michael Bloomberg (I) announces his $50 million donation aboard a boat on the Potomac River this morning, flanked by (left to right) Sierra Club Executive Director Michael Brune, Rep. Jim Moran (D-Va.) and Mary Anne Hitt, the director of the advocacy group's Beyond Coal campaign. Behind them is GenOn Energy Inc.'s Potomac River Generating Station, a 60-year-old coal plant in Alexandria, Va., that the Sierra Club is trying to close. Photo by Gabriel Nelson.

Bloomberg, who is worth more than $18 billion and was ranked the second most prolific U.S. philanthropist in 2010, has a long history of gifts to environmental groups such as the Natural Resources Defense Council and the World Resources Institute.

As mayor, Bloomberg has called for swift action to cut the carbon dioxide emissions that are linked to climate change. That has meant stricter energy efficiency codes for New York City buildings and a plan -- struck down by federal judges and appealed all the way to the Supreme Court -- to have all the city's signature yellow taxis replaced with hybrids.

Two of his main causes in the past have been tobacco and traffic safety. He said it's a natural progression to give money to the Sierra Club's "Beyond Coal" program, which aims to shift the United States to cleaner sources of electricity by shutting down old coal plants and stopping new ones.

The nine-year-old campaign currently has about 100 employees to 15 states. Today's gift will double the program's payroll, expanding it to 46 states and providing a third of the $150 million budget for the next four years, said Michael Brune, the group's executive director.

"If you're serious about ending climate destabilization and you're not fighting coal, then you're not really serious," he said during today's press conference. "We need to break our dependence on coal, and we need to do it as quickly as possible."

Among the plants being targeted is Houston-based GenOn Energy Inc.'s Potomac River Generating Station, which is in Alexandria, Va., just a few miles from Capitol Hill. It has prompted protest from Washington, D.C., Mayor Vincent Gray (D) and other local lawmakers, who say the plant's sulfur dioxide (SO2) emissions are making the air dirtier in the nation's capital.

In a statement, a GenOn spokeswoman noted that the electricity from coal plants is key on days like today, when demand for power is at its peak because of 100-degree temperatures that lead to heavy use of air conditioning. She said the company has followed all environmental laws and will decide whether to shut down the plant based on the cost of keeping it open.

Timing

The company's plant is in the district of Rep. Jim Moran, a Democrat who chairs the subcommittee that writes budgets for U.S. EPA and the Interior Department.

Moran said today that Bloomberg's gift is especially important because a spending bill headed to the House floor this month would get rid of 691 positions at U.S. EPA and block new rules for the use of coal.

"In the Congress, we're losing ground, actually," Moran said in an interview. "The only hope that we have is to mobilize the American people. This money will be used for that purpose."

Though its importance was downplayed by supporters of coal-fired power, Bloomberg's new donation comes at a tough time for coal, which is taking a hit because of new regulations, low natural gas prices and the possibility that Congress could put a price on carbon.

No new coal plants have started construction since 2008, and more than 150 projects -- all of them fought by the Beyond Coal campaign -- have been scrapped in recent years. The Sierra Club has not shied away from taking a share of the credit.

Meanwhile, power producers announced last year that they would shut down 48 plants with 12,000 megawatts of capacity, or 4 percent of the nation's coal fleet.

Several of the nation's largest coal-burning electric companies have made high-profile announcements on retirements this year. The federally owned Tennessee Valley Authority struck a settlement with states and environmental groups earlier this year to shut down 2,700 MW of coal capacity, while Columbus, Ohio-based American Electric Power Co. Inc. released a compliance plan that would lead to 5,856 MW of coal retirements in 2014.

According to estimates by the Energy Information Administration, though, the United States won't stop using coal anytime soon. The country will get 43 percent of its electricity from coal in 2035, down from 45 percent right now, the agency said earlier this year.

Today's gift was lamented by the United Mine Workers of America, which said that coal drives employment in the United States by providing low-cost electricity. Technology that would allow for "clean coal" would be a worthier use of the money than trying to get rid of all coal plants, President Cecil Roberts said in a statement.

"If he was really serious about doing something about the environment and helping to keep and expand American jobs, perhaps Mayor Bloomberg could devote his resources instead toward contributing to the development of CCS [carbon capture and storage] technology in this country, so that we can support American innovation and keep American workers on the job," he said.