According to this article in The Nation, Michael Bloomberg has donated $50 million to the Sierra Club for the purpose of taking coal plants offline and replacing them with renewable fuel sources and conservation:

Bloomberg stood in 100-degree heat on Thursday morning outside the GenOn power plant in Alexandria, Virginia. Joined by Sierra Club executive director Michael Brune, Bloomberg said he hoped his philanthropic contribution would improve public health both at the local level—by reducing emissions of the mercury, dioxin and other pollutants that are released when coal is burned—and at the global level, by limiting the severity of climate change.

“If we are going to get serious about reducing our carbon footprint in the United States, we have to get serious about coal,” said Bloomberg, according to his prepared remarks. “Coal is a self-inflicted public health risk, polluting the air we breathe, adding mercury to our water, and [is] the leading cause of climate disruption.”