University of California study evaluates ultra-low emission natural gas bus

July 27, 2017. The University of California, Riverside College of Engineering Center for Environmental Research and Technology (CE-CERT) and SoCalGas have announced the results of a new study on ultra-low emission natural gas heavy-duty engines. The study found that a Los Angeles County Metropolitan Transportation Authority (Metro) bus equipped with an ultra-low emission natural gas engine performs significantly cleaner than its certification standards across all duty cycles.

   Researchers tested the Cummins Westport ISL G near zero natural gas engine in a variety of conditions typical of a Metro bus. In all conditions, the engine performed better than California’s toughest-in-the-nation standard for smog-forming emissions. In some driving conditions emissions were practically zero.

   “We have tested two of the ISL G near-zero 8.9 liter engines, one in a refuse hauler and one in a Metro bus. In both cases, the NOx emissions were surprisingly low and 99 percent cleaner than the current standard and 99.96 percent cleaner than the 2004 standard,” said Kent Johnson, associate research engineer for CE-CERT and lead researcher on this study.

   “The near-zero engine will provide immediate NOx relief to our region at a low cost, and coupled with renewable natural gas (RNG), would provide long-term stability to our energy and climate change needs. Pursuing RNG technology is a promising and visionary pathway for California and is recommended by UCR’s RNG research center.”

   George Minter, regional vice president for external affairs and environmental strategy for SoCalGas said: “The UC Riverside data suggests that this natural gas bus is as clean as an electric bus when it comes to meeting air quality standards. And when these buses are fueled with renewable natural gas, the greenhouse gas reductions are even greater. By deploying this technology, large bus fleets like Metro’s have a tremendous opportunity to achieve clean air gains.”