Indonesian energy and mineral resources ministry has dropped plan to ban exportation of coal with calorie of less than 5,700 kilo calorie per ton due to inefficiency, an official said on Thursday.

The ministry replaced the plan with restriction on production quota of the commodity, said Prasodjo, director of coal at the ministry.

Previouly the ministry has planned to ask investors on mining to upgrade the calorie of the coal to more than 5,700 kilo calorie for the exportation.

"Nevertheless, it was not efficient. So we decided to control change it with the control of production with quota system," Prasodjo said.

Indonesia, the world's second-biggest exporter of thermal coal, has 20.8 billion tons of proven coal reserves, according to the ministry.