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Table 14 – Fuel Usage and Emission Levels for Truck, Rail, and Tug-Barge ModesModeTon miles ofFreight Carriedper Gallon ofDiesel FuelHydrocarbons(HC)Pounds of Emission per Ton MileCarbonMonoxide (CO)Truck 59 0.0063 0.0190 0.1017Rail 202 0.0046 0.0064 0.0183Tug-Barge 514 0.0009 0.0020 0.0053Source: USDOT data reported in Alabama Freight Mobility Study, April 19, 2007Nitrogen Oxides(NOx)Emission estimates by other studies have been measured as grams of pollutant emissiongenerated by each of the three modes, are shown in Table 15.Table 15 – TTI Estimates of Emissions per Ton Mile of Cargo MovedGrams of Emission per Ton-MileMode HC CO NOx PMTruck 0.020 0.136 0.732 0.018Rail 0.024 0.064 0.654 0.016Tug-Barge 0.017 0.046 0.469 0.011Source: Texas Transportation Institute, A Modal Comparison of Domestic Freight TransportationEffects on the General Public, December 2007.Greenhouse gas emission, as measured by carbon dioxide (CO2) emission can also besubstantially lower in some port areas. The International Chamber of Shipping andInternational Shipping Federation have documented the relative emission-saving potentialfrom shipping cargo on four alternative transport modes: air, trucking, rail, and barge (Table16).Table 16 - CO2 Emissions for Alternative ModesModeCO2 Grams per Ton-KilometersAir freight 747-400 1,200 km flight 540Heavy Truck with Trailer 50Marine Cargo Vessel 2000-8000dwt 21Marine Cargo Vessel over 8000 dwt 15Source: Texas Transportation Institute, A Modal Comparison of Domestic FreightTransportation Effects on the General Public, December 2007.Current research indicates that natural gas, compared to diesel fuel, reduces emissions ofNOx by about 80%, carbon dioxide by roughly 20%, carbon monoxide by approximately75%, benzene by over 95%, and VOC by over 30% 63 . For a time during 2008, some viewed63 Calculations based on interview of Alexandre Eykerma, Wärtsilä; and James J. Winebrake et al, “Energy Useand Emissions from Marine Vessels: A Total Fuel Life Cycle Approach,” Journal of the Air and WasteManagement Association, Vol. 57, January 2007, pp. 105-109.ONR SSS Final Report 59