RBCT SPECIFICATIONS FOR TYPES OF EXPORT COAL AT THE BAY . The typical coal exported from South Africa falls into two categories: RB1 . NCV (net calorific value) minimum 5850kcal/kg, with basis being 6000kcal/kg . Total moisture (as received basis) 12% max . Volatile matter (as received basis) 22% min . Ash (as received basis) 15% max