ULSD/DPF combo cuts unhealthy emissions on multiple fronts - ultra-low sulfur diesel/diesel particulate filters
Diesel Fuel News, Sept 15, 2003
by Jack Peckham
A combination of ultra-low sulfur diesel (ULSD) with catalyzed diesel particulate filters (DPFs) not only slashes "toxic" particulates and organic gases, but also helps reduce exhaust components that otherwise might cause mild lung injury or decrease lung resistance to viral infection.
U.S. Department of Energy-sponsored studies at the renowned Lovelace Respiratory Research Institute (LRRI) show that changes in diesel exhaust composition also produce a change in relative health effects, as shown in tests with laboratory rodents.
In tests, the use of a catalyzed DPF indicated a positive reduction in non-cancer health effects of diesel exhaust, beyond "toxics" reductions in many studies on DPF systems.
The studies eventually aim to produce data that would help indicate which parts of diesel exhaust can cause non-cancer health effects.
"Diesel exhaust under some conditions has been shown to produce lung inflammation and oxidative stress in healthy rodents," LRRI scientist Jake McDonald explained to Diesel Engine Emissions Reduction (DEER) workshop here.
"In addition, recent work at LRRI has shown that prior exposure to low levels of diesel exhaust decreases the ability to fight off respiratory infection. In these studies, we investigated a common virus that affects children--Respiratory Syncitial Virus (RSV)."
This virus is today the most common pathogen causing lung infections that trigger hospitalization of children under age five.
Research on how diesel exhaust changes can affect resistance to RSV may become even more significant if future health-effects investigations confirm some recent studies indicating that viral infections in young children might be related to asthma later in life.
For the emissions-effects tests, LRRI operated a Yanmar single-cylinder diesel genset engine either under constant high-load, constant low-load, or at high load with the ULSD/DPF combination.
The high load/low-load non-DPF exhausts were diluted to the same particle concentration. Tests with the DPF used the same dilution rate as with non-DPF, constant high-load test. For DPF-filtered exhaust, researchers employed a CleanAIR Systems catalyzed DPF, certified by CARB for >85% particulate matter (PM) reduction and >95% reduction of carbon monoxide (CO) and total hydrocarbons (THC).
This engine ran either on ordinary No. 2 diesel fuel (370-ppm sulfur, 29% aromatics, 47 cetane, 35.8 API gravity) or the BP-Arco "ECD" ULSD (<15-ppm sulfur, 49 cetane, 29% aromatics, 37.5 API gravity).
For each exhaust exposure test, researchers assessed particle mass, particle size distribution, and hundreds of individual gas and particle-bound components including organic compounds, metals and sulfate/nitrate.
After exposure either to diesel exhaust or filtered air for seven days at six hours/day, rodents either were injected with the RSV virus or immediately studied for lung injury without viral infections.
Tests showed that high-load engine operation produced exhaust with slightly larger particle size, less CO and less organic material than low-load condition, where organic material and smaller particles dominated.
DPF-filtered exhaust virtually eliminated the elemental (black) carbon and drastically reduced the organic carbon as well. DPF-filtered exhaust also drastically reduced CO, VOCs, and the speciated semi-volatile and heavy organics.
Exposure to high-load engine exhaust produced health effects in both the non-infected and RSV-infected rodents. Health effects decreased--but were still evident--under partial load engine operation. However, the health effects--including oxidative lung damage, lung inflammation (response to lung injury) and resistance to viral infection--weren't seen with the ULSD/DPF treated exhaust.
Following these pilot tests, LRRI will expand its investigation to include health effects of uncatalyzed DPF exhaust, lubes emissions impact during transient engine operations, and effects of spark-ignition engine exhaust.
These tests likewise could help scientists understand which exhaust components are responsible for certain health effects.
"What we're setting up is a framework for determining differences in health response to changes in exhaust composition," McDonald says. "We're asking: Can we get enough different exposure compositions, with enough different samples, to make associations with emerging statistical approaches for investigating mixtures of air pollutants?
"In addition, there are several components of exhaust including particle mass and particle size that have been implicated in increased health responses, but more evidence is necessary before we can definitively say whether either is important.
"We want to know: What are the specific exhaust components that seem to drive the health effects?" McDonald says. "We need to know this so that we can make sure our [emissions-control] regulatory approaches are handling this correctly."