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Air Quality

Published on May 29th, 2017 | by Steve Hanley

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Gas Cars Much Dirtier Than Expected

May 29th, 2017 by  


Originally published on Gas2.

For years, the conventional wisdom has been that pollution from diesel engines was far worse than from gasoline engines for two reasons: First, diesel exhaust fumes are known to contain nitrous oxide emissions. Second, they also contain particulates, small molecules that are too small to see. Both are believed to cause serious damage to human lungs.

Particulate Emissions From Gasoline Engines

Now it turns out that conventional wisdom is wrong. A study by researchers at the Materials, Science, and Technology Laboratory in Switzerland claims that particulate emissions from gasoline engines can be far greater than those from diesel engines.

The laboratory studied the emissions of 7 gas engine vehicles equipped with direct-fuel-injection systems. The research found that they emit from 10 to 100 times more particulates than modern diesel engines. In fact, they have higher particulate emissions than older diesel without particulate filters.

Wait, did you read that right? Gasoline engines spew out up to one hundred times more particulates that a modern diesel engine equipped with a particulate filter? Yes, you read that right.  Yikes. And people wonder why the incidence of asthma and other lung related diseases is on the rise!

Researchers Find Carcinogens In Gas Engine Exhaust

The researchers, led by Norbert Heeb, who has 25 years of experience analyzing emissions from diesel engines and designing filter systems, showed that the particles are the same size as those from older diesel engines. They measure between 10 and 20 nanometers and clump together into particles between 80 and 100 nanometers before they leave the exhaust system.

The gas engines were also found to discharge unburned hydrocarbons in the form of polycyclic aromatic hydrocarbons (PAHs), along with other liquid and solid toxins which accumulate on the surface of the emitted particles.

Particulates Penetrate The Lungs

Heeb says the particles are so small they penetrate lung tissue and pass into the bloodstream, bringing those toxins with them. Is this beginning to sound like the days when researchers first told the world about all the nasty stuff contained in cigarette smoke? It should, because it turns out there is a connection to smoking. The researchers also found that the exhaust gasses coming out ot the tailpipes of the cars with gas engines also contain benzo-α-pyrene, a carcinogenic produced when tobacco is burned.

A Call For Particulate Filters

He urgently suggests that carmakers begin equipping their gas-powered cars with particulate filters. “New exhaust emission technologies launched on the market typically need about 13 years to become fully effective. Only after that period of time will 9 out of 10 cars in the vehicle fleet be replaced,” he says. “So, the faster particle filters are mandatory in gasoline cars, the better it will be for everyone’s health.”

Direct Injection Is The Cause

The culprit in all of this appears to be direct-injection systems themselves. Gasoline engines do not inherently form particulates in the exhaust. In older electronic fuel injection systems with an injector located in the intake tract, fuel is added at the end of the exhaust stroke as the piston is travelling away from the combustion chamber.

In direct injection engines, the fuel is added as the piston is headed back toward the combustion chamber after the end of the intake stroke. This gives the fuel less time to evaporate, claims Heeb, which results in more more unburned hydrocarbons, which means more soot.

Direct injection allows more precisely controlling the fuel delivery process, leading to better fuel economy and lower carbon dioxide emissions. Apparently, few people have tested gas-powered cars equipped with direct-injection systems for anything other than CO2 until now.

Another Reason To Go Electric

What’s the bottom line? Just this: Thanks to the Swiss researchers, now we know that our cars are slowly killing us and the planet we live on. It is time to end the reign of the internal combustion engine and push forward with the transition from fossil fuel cars to zero-emissions electrics. Our health depends on it.

Source: TU Norway | Photo Credit: Bosch

Hat tip to Leif Hansen. 


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About the Author

Steve writes about the interface between technology and sustainability from his home in Rhode Island and anywhere else the Singularity may take him. His muse is Charles Kuralt -- "I see the road ahead is turning. I wonder what's around the bend?" You can follow him on Google + and on Twitter.



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