It said they remain unsold because there is not enough demand in the domestic market for sevaral varieites of coal.

The unsold coal was mined by state-owned Vietnam National Coal and Mineral Industries Group (TKV) and Dong Bac Corporation, with the former accounting for two million tons. 

Mineral producers are required to prioritize domestic sales, and exports require express permission from the government, which seeks to prevent the depletion of natural resources and environmental harm caused by mining.

The ministry had once sought permission in early April, but was directed to further consult ministries and enterprises before finalizing its Coal Export Plan for 2019.

The plan had to ensure economic efficiency, meet national energy security requirements and ensure maximum coal supply for domestic needs, and exports should only be of coal varieties not consumed in the country, the government had stressed then. 

According to a recent report by the ministry, from now through 2030, around 2.1 million tons of coal of certain varieties are likely to be in excess of domestic requirement every year.

These varieties, which can only be found in Vietnam, are also consumed in Japan and South Korea.

According to the General Department of Customs, Vietnam imported 23.78 million tons of coal in 2018, mainly for electricity generation.

The unsold coal produced by TKV and Dong Bac is used in steel production and are not of the varieties that Vietnam imports.