The replacement by natural gas of oil or coal used in power plants has been prop
ID: 1027296 • Letter: T
Question
The replacement by natural gas of oil or coal used in power plants has been proposed as a mechanism by which CO2 emissions can be reduced. However, much of the advantage of switching to gas can be offset since methane escaping into the atmosphere from gas pipelines is 23 times as effective, on a molecule-per-molecule basis, in causing global warming as is carbon dioxide. Calculate the maximum percentage of CH4 that can escape if replacement of oil by natural gas is to reduce the rate of global warming. [Hint: Recall that the heat energy output of the fuels is proportional to the amount of O2 they consume.]
Explanation / Answer
The ratio of the energy generated by combustion to mol of CO2 produced is roughly 4 to 3 for CH4 vs. CH2 (considered to be oil). Thus the replacement of X mol of oil by natural gas will result in a ~33% decrease in CO2 emissions. The maximum percentage leakage of CH4 needs to be held to
33%/23 = 1.4%