SYDNEY An Indian mining giant announced Tuesday the official start of a proposed $16 billion coal project in Australia that conservationists say threatens the Great Barrier Reef .

Adani Group chairman Gautam Adani said the company had approved its final investment decision regarding the controversial project in central Queensland. The 100-square-mile Carmichael mine would produce millions of tons of the fossil fuel each year.

It has faced severe backlash in the country from environmental groups who say the project would negate Australias pledges to limit greenhouse gas emissions and harm the environment particularly the imperiled reef, located off the states coast.

We have been challenged by activists in the courts, in inner city streets, and even outside banks that have not even been approached to finance the project, said Adani, who founded the energy company, at a press conference. We are still facing activists. But we are committed to this project.

In recent months, Australian officials have cleared regulatory hurdles for the project and the federal government announced it had conditionally approved a $750 million loan to help build a rail line to transport coal from the Carmichael mine to a proposed shipping terminal on the coast. At its peak, the mine would produce about 44 million tons of coal annually to ship to India. Thats enough energy to power 100 million homes.

This is a great day not just for the Queensland economy, but for the Queensland people, and our greatest asset is our people, said Queensland Premier Annastacia Palaszczuk at a press conference.

Environmentalists and scientists, however, have roundly lambasted the project and said it runs contrary to any efforts to address climate change. Australia is still party to the landmark Paris climate accord and has pledged to reduce emissions 26 to 28 percent by 2030 .

You cant be the worlds biggest coal exporter and at the same time be taking action on climate change,said Nikola Casule, a climate and energy campaigner at Greenpeace Australia. Its completely incompatible.