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Emissions From Automobiles
(What is coming out of the tailpipe?)

With close to one vehicle for every two people, Canada has one of the highest ratios of car ownership in the world. This scale of automobile use in Canada has a cost.

Most energy used to power automobiles comes from the burning of fossil fuels in the vehicle’s engine. This burning process produces emissions that pollute the air and contribute to climate change. In fact, one‐quarter of Canada’s greenhouse gas (GHG) emissions come from transportation activity.

Because of more effective pollution control devices and improved fuel formulations, the level of toxic and smog‐forming pollutants from vehicles is declining; however, the overall increase in the number of vehicles on the road is limiting potential improvements in air quality.

In order to make your vehicle run, chemical energy (in the form of fuel) is converted into kinetic energy (or motion) through combustion. In a perfectly ideal situation, complete combustion of fuel’s hydrocarbons with oxygen present in the air would produce only carbon dioxide and water; however, the real output is more complicated:

  • Emissions of unburned fuel enter the air as “Volatile Organic Compounds.”
  • Incomplete or partial combustion of hydrocarbons results in the release of “Carbon Monoxide.”
  • Since combustion occurs under conditions of high heat and pressure, nitrogen becomes bonded with oxygen to form “Oxides of Nitrogen.”
  • Sulphur in fuel also bonds with oxygen to form “Oxides of Sulphur.”
  • Varying amounts of “Particulate Matter” including soot and microscopic liquid droplets are also emitted.

These emissions contribute to negative environmental and health effects. Carbon Dioxide emissions create an “enhanced greenhouse effect,” causing the Earth’s temperature to rise. Various vehicle emissions (PM, NOx, VOCx, SO2, and CO) combine when exposed to heat and sunlight, creating ground level ozone – a major component of smog. Acid Rain occurs when sulphur dioxide and oxides of nitrogen react with water vapour to become sulphuric acid and nitric acid.