The combustion of ethanol goes according to the following equation:

where LHV = lower heating value, the symbol "L" designates liter.

1. Calculate the amount of CO₂ produced in g per MJ of energy released (LHV). The density of ethanol at 16°C is 780 g/L. The growth of corn and conversion of the corn into ethanol produce 87 g CO₂/(MJ of ethanol) from the fossil fuels required. In addition, 35 g of CO₂/ (MJ of ethanol) is produced during the fermentation of corn sugar into ethanol. However, each atom of carbon in the corn sugar, and thus each atom of carbon in the CO₂ released by fermentation of the sugar, originally came from an atom of carbon dioxide in the atmosphere. Therefore, the CO₂ from the fermentation is "carbon neutral," that is, the amount of CO₂ released by the fermentation is balanced by CO₂ removed from the atmosphere in making the corn sugar. [Note: The same is true for the fermentation of any biomass.] Likewise, each atom of C in the CO₂ produced by combustion of ethanol is also carbon neutral.

2. Calculate the total amount of CO₂ released to the atmosphere per MJ (LHV) of ethanol made from corn and combusted, and the net amount of CO₂ released per MJ (LHV) of ethanol made from corn and combusted. The net amount is the amount by which the production and combustion of ethanol increase the amount of CO₂ in the atmosphere. Gasoline is a mixture of many compounds of carbon and hydrogen, but may be represented by the formula C₈H₁₆, with an LHV of 32.8 MJ/L (L = liter).

3. Calculate the CO₂ emissions in g CO₂/MJ (LHV) with gasoline as fuel.

4. Estimate the total CO₂ emissions [g CO2/MJ (LHV)] from "well-to-wheel" by including "well-to-tank" emissions with gasoline as a fuel. The well-to-tank energy efficiency for gasoline is approximately 90% (100 × (MJ energy to tank)/ (MJ energy of petroleum "in the well")). Assume that the ratio of CO₂ emissions from tank-to-wheel is also 90% of the total CO₂ emissions.