Comparison of Regulated and Unregulated Exhaust Emissions From a Fleet of Multi-Fuel Solid Resource Collection Vehicles

The refuse truck segment of the heavy duty diesel vehicle population has been identified as the most fuel inefficient sector. This is predominantly due to the stop and go driving pattern associated with these trucks. Constantly evolving emissions norms are forcing large truck fleet operators to explore the economic viability of alternative fueled vehicles to combat the increasing operating costs in terms of retrofit requirements of heavy-duty diesel vehicles. The objective of this study was to determine the emissions benefits and the economic viability of introducing liquefied natural gas (LNG), and LNG-Ultra-low sulfur diesel (ULSD) dual-fueled vehicles into the solid resource collection vehicle fleet (SRCV) in the city of Los Angeles. The 12 vehicles tested in this study were part of a multi-fuel refuse truck fleet. It should be noted that these vehicles are not representative of the state-of-the-art advanced technology engines that power the present day fleets. Vehicles were exercised over the AQMD refuse truck cycle and a newly developed compaction cycle on a heavy-duty chassis dynamometer. Regulated emissions together with a whole spectrum of unregulated speciation including the analysis of 1,3 butadiene with an on-site gas chromatograph was performed. Results showed that PM distance-specific mass emissions from LNG-fueled vehicles were on an average 82% lower than diesel trucks equipped with a DPF. Chemical speciation of exhaust from different fueled trucks indicated a characteristic emissions profile specific to the fuel used in these vehicles. While emissions from LNG vehicles were characterized by carbonyls, and other lower chain hydrocarbon compounds, emissions from diesel vehicles were dominated by polyaromatic hydrocarbons (PAH) and higher chain hydrocarbons.