Carbon Dioxide Emission Index as a Mean for Assessing Fuel Quality

Abstract

Carbon dioxide emission index, defined as the amount of CO₂ released per unit of energy value, was used to rate gaseous, liquid and solid fuels. The direct utilization of natural gas is the most efficient option. The conversion of natural gas to synthesis gas for production of liquid fuels represents a significant decrease in fuel value of the former. The fuel value of liquids, such as gasoline, diesel oil, etc. is lower than that of natural gas. Blending gasoline with ethanol obtained either from bio-mass or via synthesis may decrease fuel value of the blend when CO₂ emissions produced during the production of ethanol are included in total emissions. The introduction of liquid fuels produced by pyrolysis and liquefaction of bio-mass would result in the increase in the CO₂ emissions. The CO₂ emissions from the utilization of coal and petroleum coke are much higher than those from gaseous and liquid fuels. However, for petroleum coke, this is offset by the high value gaseous and liquid fuels that are simultaneously produced during coking. Conversion of low value fuels such as coal and petroleum coke to a high value chemicals via synthesis gas should be assessed as mean for replacing natural gas and making it available for fuel applications.

Keywords:

• carbon dioxide emissions
• carbon dioxide emission index
• fossil fuels utilization

Notes

^a As pure compound.

^b Made from methane.

^a Made by hydrogenation of benzene using H₂ made by steam reforming of hydrocarbons.

^b Made by hydrogenation of benzene using H₂ made via gasification of solid fuels.

^c Ethanol from fermentation.

^d Ethanol made by synthesis.

^a For every gasification product, 8.8 MJ/kg (generated by partial combustion of carbon to CO) was added to the actual heating value. MAF—moisture ash free basis.