A report released by the University of California Riverside’s College of Engineering-Center for Environmental Research and Technology (CE-CERT), found that new ultra-low emission natural gas heavy-duty vehicles met and exceeded their certification standards during a full range of duty cycles. With the near-zero emission factors demonstrated for NGVs, it is expected that these vehicles could play an important role in providing much needed emissions reductions required for the South Coast Air Basin and California to reach federal air quality attainment standards.
“When comparing the data of the cleanest available heavy-duty diesel vehicles versus the cleanest available heavy-duty natural vehicles, it is clear that natural gas vehicles provide unmatched reductions of smog-forming emissions,” stated Dr. Kent Johnson, author of the report. “These near-zero emission natural gas vehicles are especially effective in applications that require low speeds, such as short-haul goods movement.”
Diesel-fueled medium- and heavy-duty vehicles are the number one source of smog-forming emissions of NOx in almost every single metropolitan region in the country. NOx emissions lead to the formation of ozone and small particulate matter (PM2.5), each of which contributes to significant health impacts. In areas with the most severe air quality problems – such as southern and central California – achieving healthy air quality will require a transition of heavy-duty vehicles to ones that emit zero or near-zero emissions.
The report authored by Johnson evaluated the Cummins Westport ISL G near-zero (NZ) engine emissions during typical in-use conditions. The engine was certified in the fall of 2016 by the EPA and the California Air Resources Board (CARB) to 0.02 g/bhp-hr, which is 90% cleaner than EPA’s current NOx emission standard and 90% cleaner than the cleanest available diesel engine.
The report tested the ISL G near-zero engine on duty cycles that represent operations in the South Coast Air Basin. These cycles included the urban dynamometer driving schedule, port cycles (including near dock, local and regional), refuse cycles, and central business district cycles. The report concludes that ISL G near-zero natural gas engines perform with NOx emissions below their certification level and that emissions decrease as the duty cycles decrease, meaning that in lower speed scenarios, such as stop-and-go traffic commonly found throughout the South Coast region, the emissions decreased.