On October 26, Beijing was stricken by a third day of extremely heavy pollution within a month. The particulate matter (PM) density in the city reached over 250 micrograms per cubic meter, nearly three times the maximum amount for safe levels, according to the Beijing Municipal Environmental Monitoring Center.

The egregious smog reduced visibility at the Beijing Capital International Airport to 300 meters at around 9 am October 27, and a total of 31 flights were canceled between October 26 and the following morning, according to reports from Xinhua and State television CCTV. The foul air hit most of North China, leading to expressway congestions and closures, the news reports said.

The hazardous effects of the fast-growing vehicle fleet in China, particularly diesel-fueled commercial vehicles such as trucks and buses, have long been a cause for concern to the public, experts and officials, and have become the subject of heated discussion recently.

"To the extent that there is data available, here in Beijing, diesel vehicles are currently the largest source of PM 2.5, at about 22 to 23 percent. In Shanghai, the same is true, maybe a little bit higher," Michael Walsh, former chairman of the International Council on Clean Transportation (ICCT), said during the US-China Clean Truck & Bus Forum in Beijing on October 30.

"Motor vehicles, specifically diesel vehicles, largely buses, are significant contributors to the urban PM 2.5 [pollution] and all of the health consequences associated with it," said Walsh.

Upgrade to LNG

Beijing suffers more than most Chinese cities in terms of PM 2.5 pollution, but it is also poised as one of the frontrunners in tackling the problem.

The Chinese capital already has the world's largest liquefied natural gas (LNG) bus fleet, at 3086 units, Beijing Youth Daily reported in July, citing data from Beijing Public Transport Holdings.

And it will soon scrap another 3,000 diesel buses and replace all of them with LNG buses, Feng Xingfu, vice general manager of Beijing Public Transport Holdings, said at the clean vehicle forum October 31.

"[In the renewal program], we will even upgrade the buses which are scheduled to be scrapped in 2015 in early 2013 or at the end of this year … It's because we have found that … diesel vehicles are the biggest contributor among motor vehicles [to the PM 2.5 measurements in Beijing], even though Beijing already uses the country's best diesel," Feng said.

An emission test conducted by Tsinghua University showed that LNG buses emitted more than 90 percent fewer micro particulates than diesel buses that meet the National 4 Emission Standard, he said.

In the next 10 years, LNG buses will become a major force in Beijing's bus fleet, including pure LNG as well as natural gas-electric hybrid buses, Feng said.

Beijing has 21,018 buses, 9,353 of which, or 44.5 percent, have yet to meet the National 4 standard, the Beijing Youth Daily report said.

China had more than 1 million LNG or CNG (compressed natural gas) vehicles by the end of 2011, and by 2015, the country will have 1.5 to 1.8 million natural gas-fueled vehicles, with 100,000 to 150,000 of them being city buses, Science and Technology Daily reported, citing experts at a natural gas vehicle forum held November 1 in Chongqing.

EVs less favored

The Ministry of Finance, the Ministry of Technology, the Ministry of Industry and Information Technology and the National Development and Reform Commission launched a pilot program to push for the use of new-energy vehicles, namely pure electric and hybrid electric vehicles, in public transportation in 13 cities and regions in China in 2009. The pilot cities and regions were expanded to 25 in 2010.

China's bus fleets are pioneers in adopting green technology in the country. By the end of 2011, new-energy buses accounted for 63 percent, and over 80 percent of these buses used hybrid electric technologies, Shanghai-based Huabao Securities wrote in a research note in October.

However, Feng downplayed the prospect for new-energy vehicles, especially electric vehicles (EVs), in the bus fleet within a decade in Beijing. The city already has 1,523 new-energy buses, but he said it would be hard to achieve the target of 5,000 new-energy buses by 2015, despite the government's determination.

There are few land plots available in the city for building battery swap stations, while high battery costs and short battery life also pose insurmountable difficulties, he said.

The batteries that were installed on 50 electric buses in Beijing during the 2008 Beijing Olympics were all disposed of at the end of 2011, and the new batteries lost about one-third of their capacities in six months, news website cqn.com.cn reported Tuesday.

There were 11,949 green vehicles in the pilot cities and regions at the end of 2011, far below the target of 52,621 units for 2012, Automotive Observer magazine reported in July.

Policy impact

Feng said that diesel buses are still the most reliable form of public transportation, but as one of the bigger polluters, the bus company has an obligation to use more clean-energy vehicles.

The control technologies for cleaning up the diesel are readily available, and they have effectively reduced particulate emissions of all diesel vehicles in the US, according to Walsh of ICCT and Steve Johnson, chief engineer of commercial vehicle exhaust systems in Asia at Faurecia, the world's largest exhaust system supplier.

The major obstacle for adopting the clean technologies in China is slow policy progress, according to the experts.

Although Faurecia has been making exhaust filters that meet the Euro 4 emission standard (equivalent to National 4) in China for export, few Chinese automakers are using them because China currently implements the National 3 standard for commercial vehicles, Johnson told the Global Times.

China decided to start implementing the National 4 standard for diesel vehicles in late 2010 but has delayed it twice, to July 1, 2013.

Now it may be further postponed to 2014 because of diesel supply problems, the Beijng Times reported October 25, citing an unnamed source at a commercial automaker.

"If we don't hear anything more at the beginning of next year, then people will again assume that it won't be implemented," Stephen Dyer, a Shanghai-based partner at US consulting firm AT Kearney, told the Global Times.

Some carmakers in China developed very competitive new products early on to meet the expected new standard, but because the standard has been delayed, these companies have lost their advantage, Dyer said.

"It's had a big impact on the market," he noted.