Diesel retrofit technologies and experience for on-road and off-road vehicles

Published: 2017.06.13

Joseph Kubsh, independent consultant

Diesel engines are important power systems for on-road and off-road vehicles. These reliable, fuel-efficient, high-torque engines power the vast majority of the world’s heavy-duty trucks, buses, and off-road vehicles. While diesel engines have many advantages (e.g., good fuel efficiency, long operating lifetime), they have the disadvantage of emitting significant amounts of particulate matter (PM) and oxides of nitrogen (NOX) into the atmosphere. Companies that manufacture emission controls have responded to the challenge of reducing air pollution from the in-use diesel vehicle fleet by developing a large portfolio of retrofit emission control devices. Many of these diesel retrofit technologies are similar to the advanced emission control technologies that are now available on newer “clean” diesel engines used in highway and offroad applications including diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) for reducing diesel PM; and urea-selective catalytic reduction (SCR) systems for reducing NOX. In both the on-road and off-road sectors, diesel retrofit technologies have demonstrated their ability to significantly reduce unwanted emissions from older diesel engines at reasonable cost without jeopardizing vehicle performance.

This report summarizes important features and experiences of successful retrofit program efforts primarily in the U.S. and Europe, as well as highlighting the range of retrofit technologies that have been successfully used to reduce exhaust emissions (including diesel particulate and NOX emissions) from older, existing on-road and off-road diesel engines. This report focuses the retrofit technology discussion on the experience with high efficiency retrofit diesel particulate filters and SCR retrofits, since these retrofit technologies provide the highest reduction efficiencies for diesel particulates and NOX emissions. Diesel retrofit technology verification protocols have been established in both the U.S. and Europe to ensure retrofit technologies provide proven and durable emission reductions. Other important aspects of successful retrofit programs (in addition to using verified technologies) include an application engineering approach that selects the appropriate retrofit technology based on the vehicle/engine application, its duty cycle and available fuel quality, continued maintenance of the engine and retrofit technology, professional installation of the retrofit device, and training programs for end users. The report includes web links to a wide range of information and experience concerning retrofits on both on-road and off-road diesel engines and vehicles.

Staff contact: Zhenying Shao