In 2009, US coal-fired power plants supplied 6.8 x 10^15 BTU of electricity to m

Question

In 2009, US coal-fired power plants supplied 6.8 x 10^15 BTU of electricity to meet the country's energy needs. The average coal-fired power plant is only 33% efficient, largely due to heat losses. By recovering some heat energy, the efficiency of coal-fired power plants can be increased to above 50%. How many fewer tons of CO2 would be emitted into the atmosphere to produce the same amount of electricity if all coal-fired power plants were 50% efficient? *Assume the chemical structure of coal to be C45H2O5, the energy content of one ton of coal to be 22.4x10^6 BTU, and 1 ton = 9.1x10^5 grams

Explanation / Answer

C4H2O5 + 2O2====> 4CO2 + H2O

MW = 130 g/mole, produces 4 moles of CO2/mole of coal

(6.8*1015 BTU/0.33) / (22.4*106 BTU/ton) * (9.1*105 g/ton) /(130g/mole) * (4molesCO2/mole of coal) * (44g/mole) / (1 ton/9.1*105 g) = tons of CO2

= 1.245*109 tons of CO2 = 1.245 billion tons of CO2

(6.8*1015 BTU/0.50) / (22.4*106 BTU/ton) * (9.1*105 g/ton) /(130g/mole) * (4molesCO2/mole of coal) * (44g/mole) / (1 ton/9.1*105 g) = tons of CO2

= 8.220*108 tons of CO2 = 822 million tons of CO2

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