Energy Efficiency and CO sub(2) Emissions of Road Transportation: Comparative Analysis of Technologies and Fuels

The energy consumption balances and carbon dioxide emission implications of conventional transportation fuel refining and consumption routes are evaluated. Similar assessments are made of alternative energies for road transportation, including LPG, ethanol, natural gas, and synthetic- or biofuel-based fuel additives. The use of cryogenic hydrogen with a fuel cell converter is determined to emit double the CO sub(2)/km than the direct use of natural gas in an internal combustion engine. Fuel cell-powered vehicles with hydrogen fuel offer efficiencies 66% higher than those with spark ignition engines.