California Air Resources Board

Principal Investigator/Author: Christopher Sharp

Contractor: Southwest Research Institute

Contract Number: 19RD025

Project Status: Completed

Relevant CARB Programs: Air Pollution, Heavy-Duty Low NOx

Topic Areas: Reduced NOx Standards

Research Summary:

To minimize the adverse health effects of emissions from off-road diesel engines, CARB has adopted four increasingly stringent tiers of regulations since 1995. However, it has been almost 14 years since the off-road diesel standards were last updated (Tier 4 in 2005), which now lag behind the European Stage V standards in stringency. Under current regulations, off-road diesel engines are expected to contribute 95 tons per day (tpd) oxides of NOx and 3.1 tpd PM to the California emissions inventory in 2030, making off-road diesel the single largest source of mobile emissions in California. It is imperative, therefore, that action be taken to mitigate the adverse impacts of off-road diesel emissions by adopting more stringent NOx and PM emission standards in the near term.

The objective of this project is to design, procure, age, and optimize advanced NOx and PM aftertreatment technologies for incorporation on a new Tier 4 off-road diesel engine; with the goal of reducing NOx emissions by 90 percent and PM emissions by 75 percent below Tier 4 final standards. The project will explore methods to help reduce any associated fuel economy penalties, providing CARB with an optimized low-NOx and low-PM configuration to support future Tier 5 standards.

Keywords: off-road engines, low NOx, off-road diesel, NOx standards, PM standards, mobile emissions, particulate matter, PM, emissions, heavy duty vehicle, tier 4 standards