Nitrogen oxide key to battling smog

Nitrogen oxide, more than other major pollutants such as sulfur dioxide or ammonia nitrogent, should be considered as the major culprit for smog, said Wang Yuqing, deputy head of Committee of Population, Resources and Environment of China.

"As much as 80 percent of smog that has been plaguing most of the cities are secondary pollutants, including sulfate and nitrate - fine articles that are really toxic and a threat to human health," he said during a keynote speech at an international consultative conference on NOx emission management and control, which was held on March 29 in Beijing.

The meeting was co-sponsored by International Energy Conservation Environmental Protections Association, or IEEPA, a non-governmental organization dedicated to help push forward China's green transformation.

According to Wang, these pollutants are actually transformed from sulfur dioxide and ammonia nitrogen after undergoing a series of chemical reactions, a process remarkably catalyzed by nitrogen oxide, or NOx.

NOx is one of the key airborne pollutants and main cause of acid rain that comes mainly from coal consumption and emissions of motor vehicles, he added.

Air pollution has increasingly become a major concern among Chinese people, as much of the country was time and again shrouded by the blanket of smog this year and last year, with Beijing and Hebei province bearing the brunt.

Statistics show that nitrogen oxide emissions had been growing at an annual rate of 5 to 8 percent in the past few years, but then dropped slightly as of 2012 when NOx emissions stood at about 23.4 million tons, still 30 percent more than five years earlier.

Nitrogen oxide emissions, if not properly contained, are expected to hit 35.4 million tons by 2030, and will further put our health in jeopardy, according to Jiang Minglin, counselor of the State Council, the cabinet.

"One thing we cannot ignore is that motor vehicles, aside from coal consumption, contribute as much as 50 percent to total NOx emissions in mega cities such as Beijing, Shanghai and Guangzhou. That's a huge number," said Wang.

"Mobile sources of NOx, including cars, ships and trains, are difficult to control due to their strong mobility, and has become a blind spot in curbing air pollution," said Jon Li, secretary general of IEEPA.

Inland navigation and railway transportation have been booming in the past few years. Last year, nearly 30 ports saw a throughput of over 200 million tons, some even hitting 800 million tons. Meanwhile, volume of railway freight reached 3.2 billion tons in the same period.

"Behind such a rosy picture hides a huge amount of emissions that weigh heavily on the country's air quality," said Cao Dingliang, general manager of Jiangsu Lvyuan Environmental Protection Technology Co Ltd.

"We have to step up efforts in high-tech innovations to enable green transportation in a bid to contain smog and haze," he added. "Environmental protection should be part of companies' social responsibility."

The company has blazed a trail in the field with a selective catalytic reduction system that aims to reduce and purify nitrogen oxides and sulfur oxides emissions by diesel engines with large power, with the maximum conversion rate from NOx to clean gases able to reach up to 95.7 percent.