Study of Emissions from Yard Tractors Using Diesel and LNG Fuels

August 2007

Yard tractors are the workhorse of the cargo handling equipment (CHE) and there are over 1,500 in the Ports of Los Angeles and Long Beach. Because of their high numbers and frequent use, they also are the primary contributor to the emissions inventory from cargo handling equipment. Over 50% of the NOx and PM emissions associated with CHEs come from yard tractors. Based on these facts the POLB, LBCT and WestStart-CALSTART launched an investigation of the emission factors from yard tractors. There were two goals: first, measure the emission factors from a series of engines certified to ever increasingly more stringent emission standards, and second, investigate the emissions from an engine running on an alternative fuel, LNG. As direct emissions values are scarce, the report compares the results with earlier studies and EPA certification values. A number of yard tractors with various engine technologies meeting different levels of EPA emission standards were part of the planned project as shown in the table below. The test matrix represented engines meeting Tier 1 and 2 non-road (industrial) standards, on-road (automotive) standards for 2004 and an engine fueled with LNG.