If all of the United States' annual electricity requirement of 31012 kWh was produced by coal power plants, how many tonnes of coal would be burned per minute? Assume an efficiency of 45% and energy content of 35 MJ/kg for anthracite coal. This grade of coal typically is 90% carbon and 10% moisture. How many tonnes of CO2 will be produced each second from burning it in the power plants at the rate you calculated? For that you will need to calculate some molecular weights, which you can do knowing: MW(C) = 12 g/mol, MW(O) = 16 g/mol.