Air

Nitrogen oxides

Nitrogen oxides are nitrogen-oxygen compounds produced mostly by burning fossil fuels.

Air quality especially in large urban centers is affected by pollutants from the burning of fossil fuels in vehicles, homes, factories, power plants and other sources. Nitrogen oxides react with volatile organic compounds (VOCs) in sunlight, especially in the summer months, to form ground-level ozone. Ground-level ozone can:

• aggravate asthma and respiratory problems
• increase the risk of heart disease
• damage vegetation and decrease the productivity of crops

Ground-level ozone is a key ingredient in smog (a common term for urban air pollution). Smog can affect our health by irritating the eyes, nose and throat, and worsening respiratory and heart problems.

Nitrogen oxide emissions, which produce nitric acid, also contribute to acid rain.

Reducing the impacts of nitrogen oxides is a complex challenge. Industry and government continue to target efforts to reduce emissions through new equipment, fuel efficiencies and emission reduction programs. Since the 1980s, Canada’s overall nitrogen oxide emissions have increased only slightly, remaining steady at over two million tonnes a year. But Eastern Canada’s air quality is also affected by sources (vehicles, fossil fuel-burning power plants and industries) in the U.S. About half of the acid rain and smog-producing emissions affecting this region come from U.S. sources. Further action against nitrogen oxide emissions will depend on the cooperation of the U.S.

The electricity industry’s share of Canada’s nitrogen oxide emissions is about 11 per cent. Most of these are from Alberta, Saskatchewan, Ontario, Nova Scotia and New Brunswick, where fossil fuel generation is the primary or an important source of electricity.

Industry uses innovative combustion technologies to control nitrogen oxide emissions:

• Low NOx burners reduce nitrogen oxide emissions by lowering flame temperatures in boilers. The burners can achieve emissions reductions between 30 per cent and 50 per cent.
• Selective-Catalytic Reduction (SCR) processes inject an ammonia agent that reacts with nitrogen oxides, producing nitrogen and water. These processes can remove up to 80 per cent of emissions, but capital costs of this technology are high.