Ultra-Low Sulfur Diesel Fuel
Ultra-low sulfur diesel (ULSD) is diesel fuel with 15 parts per million or lower sulfur content. The U.S. Environmental Protection Agency requires 80% of the highway diesel fuel refined in or imported into the United States (100% in California) to be ultra-low sulfur diesel. One hundred percent must be ULSD nationwide by 2010.
Currently, the vast majority of ultra-low sulfur diesel is produced from petroleum. However, biodiesel (along with some emerging advanced fuels) is inherently ultra-low sulfur and could help meet ULSD requirements in the future.
Ultra-low sulfur content in diesel fuel is beneficial because it enables use of advanced emission control technologies on light- and heavy-duty diesel vehicles. The combination of ULSD with advanced emission control technologies is sometimes called "clean diesel."
Nitrogen oxides and particulate matter are the two most harmful diesel pollutant emissions. These emissions can be controlled with the use of catalytic converters and particulate traps. However, sulfur—in amounts that used to be allowable in diesel fuel—deactivates these devices and nullifies their emissions control benefits. Using ULSD enables these devices to work properly.
Visit the Alternative Fuels and Advanced Vehicles Data Center to learn more about ultra-low sulfur diesel.