Final answer:
Natural gas combustion produces less CO2 emissions per unit of energy than coal because of its higher energy density and lower CO2-to-fuel mass ratio, making it a cleaner alternative for energy generation.
Step-by-step explanation:
When comparing the CO2 emissions from the combustion of different fossil fuels, natural gas is substantially more efficient than coal. Each kilogram or Joule of coal combusted releases more CO2 than the same amount of natural gas due to coal's lower energy density and higher CO2-to-fuel mass ratio. Specifically, coal has an energy density of 5-8 kcal/g and a CO2-to-fuel mass ratio of 3.67, whereas natural gas has a higher energy density of 13 kcal/g and a lower CO2-to-fuel mass ratio of 2.75.
By switching from coal to natural gas for energy production, CO2 emissions could be directly reduced because natural gas produces less CO2 per energy unit than coal. While every fossil fuel emits approximately 3 units of CO2 for every unit of fuel, the actual amount of CO2 released differs due to the intrinsic properties of the fuels. The substitution of natural gas for coal in energy generation is advocated as a means to decrease CO2 emissions and lessen the environmental impact associated with coal's additional pollutants like sulfur dioxide, nitrogen oxide, and mercury.