‘Clean diesel’ myth breaks down

The heyday of so-called “clean diesel” is fading in the aftermath of a series of emissions rigging scandals by global carmakers.

According to the Ministry of Land, Infrastructure and Transport, there were 883.9 million registered diesel cars as of last month, about 89 percent of all gasoline vehicles. When it comes to new cars registered last year, the number of diesel cars surpassed gasoline cars, albeit by only 2,931. Seven out of 10 imported vehicles sold in Korea are now diesels.

It was government incentives that propelled diesel cars to achieve such rapid growth in recent years. Starting in 2009, the government exempted tax for pollution by diesel vehicles meeting the European emissions standards on the grounds that diesel cars pollute less.

The bigger the engine displacement of a car, the bigger the tax levied upon it. Owners have been saving an annual tax payment of 100,000 won to 300,000 won ($83.92 to $251.76) thanks to this exemption, and under the current regulations, the exemption is set to last until 2019 for cars certified as compliant with Euro 5 and Euro 6 exhaust emissions standards.

The government-run system of issuing “low-pollution vehicle” certificates, meant to encourage more citizens to buy eco-friendly vehicles, including diesel, also contributed to the rise in sales of diesel cars. Owners of cars with the low-pollution mark are exempted from congestion fees and are eligible for 50 percent discounts when using a public parking space.

“It is very natural that people are led to consume in a sector where the government offers incentives,” said Jung Kwang-ho, professor at the graduate school of public administration. “That’s why it is high time that Korea revise its incentive system for diesel vehicles.”

Clean diesel dates back to 1997, when Toyota unleashed the Prius hybrid. The innovation of this model triggered interest in eco-friendly cars and led many to speculate that combustion engines, powered by fuels such as gasoline and diesel, would be entirely gone in the near future.

Meanwhile, German carmakers, with over 100 years of experience developing combustion engines, began paying attention to the efficiency of diesel engines. Even though diesel engines discharge relatively large amounts of nitrogen oxide (NOx) pollutants, they are able to deliver better fuel economy and power. German brands concluded that if they could tackle the nitrogen oxide issue through a separate device, they could create a fuel-efficient, clean car.

They came up with measures to reduce the toxic output. One was installing exhaust gas recirculation (EGR), a process of feeding exhaust gas back into the combustion chamber in a carefully regulated way. The other was adopting either lean NOx trap (LNT) or selective catalytic reduction (SCR) devices to filter the pollutants out. The problem is that these two devices require expensive platinum, which led carmakers to contemplate measures that would allow them to use as little of it as possible.

The myth of clean diesel began to crack long before the Volkswagen scandal broke last year. In 2012, the World Health Organization published a report that diesel exhaust fumes may cause lung cancer. The Health Ministry of Canada re-affirmed this finding through an independent review of the science, concluding that diesel exhaust also causes adverse respiratory, cardiovascular and immunological effects. The South Coast Air Quality Management District, which regulates air pollution in the Los Angeles Metropolitan Region, discovered 68 percent of airborne toxic risk is attributable to diesel engines. According to the Korean Ministry of Environment, 22 percent of all smog caused within the country comes from cars, and that figure goes up to 43 percent when it comes to the Seoul Metropolitan area.

“Engines discharge different kinds of pollutants,” said Lee Sang-hyun, professor of automotive engineering at Daeduk College, “and even among diesel cars, the quantity of exhausts vary according to models.”

According to a 2014 report from the Metropolitan Air Quality Management, however, the fine dust caused by the abrasion of car tires is 20 times more than the dust emitted from diesel engines.

Will clean diesel in any real sense ever be possible? Sunwoo Myungho, professor of automotive engineering at Hanyang University, said reducing NOx to a great extent is plausible but that it would likely be too expensive, in turn making diesel cars more expensive and therefore less popular.

BY LEE SOO-KI, SEO JI-EUN [seo.jieun@joongang.co.kr]