Metro Manila (CNN Philippines, October 16)— President Rodrigo Duterte renewed his call for the private sector to invest in clean energy during the opening of a coal-fired power plant.

“To our friends in the private sector, I ask you to follow the lead of San Buenaventura power by investing in the generation of clean energy,” Duterte said Wednesday at the switch-on celebration of the San Buenaventura Power Ltd. Co. plant.

But unlike other coal plants, San Buenaventura said its power plant uses technology that significantly reduces emissions.

“You actually burn the coal more efficiently because of the high pressure high temperature that the plant operates at,” said Rogelio Singson, president of MGen.

SBPL is a limited partnership between MGen, Meralco's power generation arm; and New Growth BV, a wholly-owned subsidiary of Electricity Generating Co. of Thailand

The 500-megawatt plant is expected to amp up energy supply in Luzon.

“I am truly pleased that this participation has led to the construction of this environment-friendly power generation facility, which will not only help in the development of our community in Mauban, Quezon, but more importantly augment the current level of power supply in Luzon,” Duterte said.

Environmental groups like WWF or World Wide Fund for Nature and Greenpeace, however, say there is no such thing as "clean coal." They are calling for a shift away from fossil fuels and "unworkable technologies" towards energy efficiency and renewables like wind and solar power.

CNN Philippines Correspondent Paolo Barcelon contributed to this report.