The Department of Environment and Natural Resources (DENR) said that the estimated 900,000 passenger tricycle units in the country operate on two-stroke engines that emit smoke that is more dangerous than those emitted by other means of transportation.
A two-stroke engine has an uncomplicated design, having fewer parts to maintain and is less expensive. However, the engine is considered highly pollutive. Since the exhaust is forced out from the combustion chamber by the inflow of the air-fuel mixture to the motion of the piston, the two-stroke engine is more likely to emit unburned gases.
To this, DENR Secretary Heherson Alvarez has pushed for amendments to standards on allowable emission of tricycles.
Under RA 8749 or the Clean Air Act, a six-percent emission limit was set for this year, which will be reduced to 4.5 percent on Carbon Monoxide (CO) for such vehicles next year. The law sets hydrocarbons (HC) at Euro I standards that measure emissions in metric units (grams/km).
Alvarez is suggesting that a four-stroke engine be used instead of the traditional two-stroke engine in passenger tricycles.
"We are trying our best to effectively cover all aspects of the Clean Air Act’s implementation. We ask tricycle owners and operators in the country to actively participate in cleaning the air," he said.
The four-stroke engine is considered the latest trend in motorcycle engines that has a higher combustion temperature, emitting only well burned gases. Its combustion occurs every two rotations of the crackshaft due to the operation of valve system.
The four-stroke engine does not emit white smoke and consumes less fuel if maintained properly. However, it has more parts to maintain and is slightly more expensive than two-stroke engines.
According to the DENR, white smoke from tricycles and motorcycles consist of unburned fuel emitting hydrocarbons in the air. Hydrocarbons are a combination of hydrogen and carbon commonly found in the aromatic component of fuel such as benzene, which is a colorless gas known for its complex and almost indestructible chemical structure.
Based on the US-Environmental Protection Agency (US-EPA), benzene is highly carcinogenic. It is emitted largely by chemical plants, industrial processes, motor vehicle emissions, and building materials.
The Department of Health had earlier warned the public on benzene’s effect although very few households were found to have significant exposure to benzene.
Another pollutant emitted by motor vehicles is carbon monoxide that affects the cardiovascular and nervous systems, and even causes heart diseases, headaches, dizziness and fatigue.