In an address at the Advanced Research Projects Agency – Energy’s Energy Innovation Summit in Washington DC, Bloomberg said the death of coal was being driven by the need to address climate change and the low price of natural gas.

“Even though the coal industry doesn’t totally know it yet or is ready to admit it, its day is done,” Bloomberg said.

“Here in the US, I’m happy to say, the king is dead. Coal is a dead man walking.”

Bloomberg added that public health and climate change activists were ready for a long “regulatory trench war” over coal-fired power.

Coal is still the leading supplier of electricity in the US.

It accounted for 37.4% of the nation's electricity last year, according to US Energy Information Administration statistics released on Tuesday.

But Bloomberg noted the US still had a long way to go to achieve “the sustainable future that we all want”

Coal-fired power plants make up 79% of carbon emissions from electricity generation, according to the EIA.

Bloomberg commented that while one-sixth of those facilities were slated for retirement, it still left a majority standing.

He has been a vocal advocate for killing coal-fired power, with Bloomberg Philanthropies recently awarding a $50 million grant to Sierra Club’s Beyond Coal campaign, which aims to retire one-third of the nation’s coal-fired fleet by 2020.

According to the Sierra Club, 142 coal plants representing more than 50,000 megawatts of coal-fired power have been retired or slated for retirement since 2010.

Meanwhile, at a University of California Los Angeles symposium Villaraigosa announced that LA would aim to remove coal-based energy completely.

“In a couple of weeks I will sign an agreement to take the city off coal by 2025. It will be a big deal,” Villaraigosa said, describing it as one of his proudest accomplishments.

The urban sustainability in North American cities symposium saw Villaraigosa sit on a panel with former Toronto mayor David Miller and Institute of the Environment and Sustainability director Glen MacDonald.

A coal-free LA has been on Villaraigosa’s mind for some time.

In his second inaugural address in July 2009, Villaraigosa set “five goals for four years”

One of those goals was to “put LA on a path to permanently break our addiction to coal”

He said he aimed to have LA coal-free by 2020 because “the threat of climate change, carbon regulation and ever-growing demand for oil from China and other developing countries will make our dependence on fossil fuels unsustainable in the long term”