CoalIndonesia has an estimated 4.2 billion tons of proven coal reserves, and an additional 12.9 billion tons in inferred reserves. Most of the reserves are found in eastern and southern Kalimantan and southern Sumatra. The production of coal experienced a decline in the 1970’s due to the promotion of subsidized petroleum. The drop in production lead to efforts to encourage its use in local cement and electric plants, and by 1990 total production had risen to 11 million tons.