California Air Resources Board

Principal Investigator/Author(s): Thomas Durbin

Contractor: University of California, Riverside

Contract Number: 21RD018

Project Status: Completed Mar 2024*

Relevant CARB Programs: Climate Change, Air Pollution, Heavy-Duty Vehicles

Topic Areas: Reduced NOx Standards, Greenhouse Gas Emission Inventory

Research Summary:

Over the next 30 years, mobile source emissions must be reduced in California to meet federal and state ambient air quality standards and other health and climate goals. The 2020 Mobile Source Strategy anticipated an overall statewide nitrogen oxides (NOx) emissions reduction of 514 and 588 tons per day in 2031 and 2037 respectively, which are equivalent to 73 and 82 percent reductions from the 2017 baseline NOx emissions. The strategy also plans to reduce mobile source fuel consumption by 9.5 billion gallons of gasoline and 3.0 billion gallons of diesel equivalent in 2045. Lowering NOx from the heavy-duty fleet is a California Air Resources Board (CARB) priority within its broader mission. There is a critical need to conduct emissions measurements to better characterize Optional Low NOx engine emissions and to understand how their benefits manifest with age and across duty cycles.

The objective of this research is to characterize real-world NOx, ammonia (NH3), and carbon dioxide (CO2) emissions of Optional Low NOx engines that meet the optional 0.02 g/bhp-hr NOx standard by vocation and duty cycles from in-use trucks operating in their natural course of business in California. As part of this study, the University of California, Riverside College of Engineering, Center for Environmental Research & Technology (CE-CERT or Contractor) will deploy sensor-based on-board sensing and reporting (OSAR) systems on 100 Optional Low NOx vehicles certified to the optional 0.02 grams per brake horsepower hour (g/bhp-hr) NOx standard (CARB, 2013). The optional low NOx vehicles will be selected primarily from three vocations but not limited to: drayage trucks, refuse trucks, and delivery trucks. The OSAR systems deployed for this project will incorporate NOx, NH3, and CO2 sensors, a global positioning system (GPS), and an engine control unit (ECU) data logger for real-time data collection. The NOx sensors will include both state-of-the-art sensors and emerging technology NOx, NH3, and CO2 on-board sensors that are production-ready or in production-intent development. Additionally, one vehicle in each vocation will be instrumented with a Portable Emissions Measurement System (PEMS) to collect real-world testing for one day.

Keywords: advanced onboard sensors; NOx emissions; CO2 emissions; optional low NOx standards