New study shows natural gas engine can dramatically reduce smog from heavy-duty trucks

August 31, 2018. The University of California, Riverside College of Engineering Center for Environmental Research and Technology (CE-CERT) and Southern California Gas Co. (SoCalGas) announced the results of a new study on ultra-low emission natural gas heavy-duty engines, showing a new 11.9-liter engine achieved California's lowest smog-forming emissions standard, and maintained those emission during all types of driving. The study results underscore the ability of the near-zero truck engines to clean the air: most heavy-duty vehicles on roads today are predominantly diesel-powered and represent one of the largest sources of nitrogen oxide (NOx), or smog-forming, emissions and fuel consumption in North America. By contrast, the new near-zero emissions 12-liter engine, made by Cummins Westport, is the only heavy-duty engine in the category to not only meet, but exceed, the California Air Resources Board's cleanest optional low-NOx standard of 0.02 g/bhp-hr.

   Kent Johnson, assistant research engineer at CE-CERT, led the tests on the near-zero emissions natural gas engine. The evaluation included regulated and non-regulated emissions, ultrafine particles, global warming potential, and fuel economy. The testing was performed during in-use testing on a dynamometer that simulated various types of driving conditions, from pulling into a loading dock to regional hauling. Johnson performed similar testing on an 8.9-liter near-zero natural gas engine last year. Those results found the smaller engine had even lower emissions than California standards will require in the near future—in some driving conditions, almost zero.

   "The first study was a smaller engine intended for use in school buses and trash trucks, which are only about 30 percent of the heavy-duty inventory. The new engine is for drayage and movement of goods, or 70 percent of the inventory. This engine technology is good not only for the smaller work-force applications of transit and refuse, but also for hauling loads around Southern California," Johnson said.

   "The transportation sector accounts for more than 80 percent of smog-forming emissions in California," said Sharon Tomkins, vice president of customer solutions and strategy for SoCalGas.  "The test results from UC Riverside once again shows the latest natural gas engine technology, which is available and on the road today, will play a vital role in achieving California's clean air goals."