Beijing is replacing a high proportion of diesel buses, which contribute higher emission of PM2.5 with airborne particles less than 2.5 microns in diameter, with new clean energy buses, Beijing News reported.

The city plans to buy 3,155 LNG (liquefied natural gas) buses and the vehicle is estimated to take over half of the total buses in operation by 2015, according to the Beijing Municipal Commission of Transport.

The paper said clean energy buses can reduce PM2.5 emissions by 97 percent compared with diesel buses. It conducted a test of PM2.5 emission at a bus transit hub station with Chen Guanghui, a volunteer from non-government environmental protection organization Nature University. It showed that readings of PM2.5 jumped to 557 from 80 micrograms per cubic meter in idle mode, and surged to 4,180 high after pushing down the pedal.

Same tests of a LNG bus showed that PM2.5 readings only increased from 30 to 40 micrograms per cubic meter before and after acceleration.