Research Publications

The purpose of this study was to perform a comparative lifecycle analysis of low sulfur diesel, compressed natural gas, and electric baggage tractors for United Airlines’ seven domestic hubs (SFO, LAX, DEN, IAH, ORD, EWR, and IAD). Both baggage tractor manufacturing burdens as well as fuel and electricity consumption burdens were modeled for the three different technologies. Due to a lack of baggage tractor specific fuel consumption and production data, this study relied heavily on information and assumptions in the GREET lifecycle model; MHDVs were used as proxies for determining CNG and LS diesel baggage tractor fuel consumption and emissions and an electric and ICEV pickup truck were used as proxies to model the production burdens of baggage tractors. Electricity generation mixes were approximated using NERC subregion mixes and eGrid data. The model shows that electric baggage tractors at each hub emit more vehicle lifecycle PM10 emissions compared to CNG and LS diesel baggage tractors. Electric baggage tractors at most hub airports emit lower lifecycle GHG emissions compared to CNG and LS diesel baggage tractors, with the exception of electric baggage tractors at DEN and ORD airports emitting higher lifecycle CO2 emissions compared to CNG tractors. Electric baggage tractors at DEN and ORD also emit higher SOx emissions as compared to the fossil fuel baggage tractors, and electric baggage tractors at EWR and IAH emit more SOx as compared to LS diesel. It is recommended that electric baggage tractors be used at SFO, LAX, IAH, EWR, and IAD airports, and CNG baggage tractors be used at ORD and DEN airports.