With greater gas mileage come harmful carbon particulates — report

Source: Benjamin Hulac, E&E reporter • Posted: Friday, October 3, 2014

Modern engines that directly transfer fuel into vehicles’ combustion chambers have let automakers churn out high-performance cars and meet stringent government fuel efficiency targets.

But according to new research on particulate emissions from the Fuels, Engines and Emissions Research Center at Oak Ridge National Laboratory, the grass underlying these instruments — officially known as gasoline direct-injection engines, or GDIs — may not be as green as environmentalists might hope.

Gasoline direct-injection engines make up 30 percent of the new-car-sales market and are predicted to reach 50 percent market share by 2017.

Increased market penetration aside, GDI engines emit 5 to 10 times more particulates than port fuel-injected engines, an earlier engine design, according to the report.

“We’re interested in it from a fuel effect standpoint,” said the study’s lead researcher, John Storey, adding that 80 to 90 percent of the particulate matter emitted during his team’s testing was soot. The remaining particulates were organic chemicals and carcinogens, he said.

Often called “black carbon,” soot is the byproduct of wildfires, stoves, chimneys and other combustion sources. Though the majority of the world’s soot emissions originate in emerging markets, U.S. EPA estimates 52 percent of soot emissions in the United States come from mobile sources, “especially diesel engines and vehicles.”

Black carbon is widely considered one of the most potent drivers behind climate change, though estimating just how much lingers in the atmosphere is a challenging task and figures vary.

Human health hazards

“The strength of it as a climate forcer varies wildly,” Storey said of black carbon as a heat-trapping influence.

He added that the “landscape of particulate matter from vehicles” is shifting and automakers are aware of particulate emissions as a pressing topic, alluding to research papers he saw emerge beginning in 2002.

In 2007, the federal government handed down energy policies to curb emissions from diesel-propelled vehicles — which, on average, are more fuel-efficient but bigger carbon polluters than their gasoline counterparts — triggering an influx of cleaner engines and exhaust filters under diesel hoods.

Diesel truck filters, according to Storey, emit “almost zero black carbon.” Before the 2007 policies came down, he said, diesel vehicles would emit 20 to 30 times more particulates.

Storey and his colleagues’ work raises serious health concerns.

Smaller particulates can penetrate the human respiratory system, burying themselves in lung cells and even entering the bloodstream, Storey said. Particulates expelled from cars with GDI engines are smaller and more varied in size, according to a statement from the Oak Ridge Laboratory, and contain more elemental carbon than the substances spewed from diesel engines.

“Larger particles tend to be scrubbed out by your respiratory system,” he said, referring to nose hair, mucus and other natural guards against foreign microbes.

Vehicle emission standards have improved dramatically in recent decades, though the advent of diesel filters has come at the sacrifice of poorer fuel economy.

“We tend to have lower overall emissions in every category,” Storey said of America’s vehicle emissions.