Energy Content and Alternative Jet Fuel Viability

This paper examines the chemical composition and energy content of several fuel options that could hypothetically be used with the existing fleet of aircraft. Fuel specific energy (energy per unit mass) is an important consideration in determining alternative-fuel viability, because aircraft must travel fixed distances before refueling. Since most aircraft fly with excess tank capacity, fuel energy density (energy per unit volume) is of secondary concern relative to specific energy. A first-order approach using the Breguet-range equation shows that the fleet-wide use of pure synthetic paraffinic kerosene fuels, such as those created from Fischer-Tropsch synthesis or hydroprocessing of renewable oil sources, could reduce aircraft energy consumption by 0.3%. Conversely, fuels with reduced specific energy, such as fatty acid methyl esters (biodiesel and biokerosene) and alcohols, will result in increased fuel volume usage and also a decrease in fleet-wide energy efficiency. No penalty in energy efficiency would occur were these fuels used in ground transportation; thus, fatty acid methyl esters and alcohols are better suited to use in ground-based applications.