Air

Sulphur dioxide and nitrogen oxides

Sulphur dioxide is produced by the burning of hydrogen sulphide and other sulphur compounds found in oil and gas. Nitrogen oxides result from the burning of natural gas, oil and other fossil fuels.

Sulphur dioxide emissions, along with nitrogen oxides, combine with water in the atmosphere to form acidifying compounds. These are later deposited on the earth’s surface and can cause acidification of soil and lakes. Many areas of Western Canada have alkaline soils that tend to neutralize “acid rain” effects. In sensitive wetlands, such as nutrient-poor bog areas in northern Alberta, nitrogen oxide emissions may cause the rapid growth of bog mosses, resulting in potential changes to the ecosystem.

The industry emits sulphur dioxide from a variety of sources, including sour gas production, flaring at oil facilities, gas plants, well-testing flares and oilsands facilities. Nitrogen oxide emissions are associated with a wide range of activities, including vehicle emissions, oil sands mining and the burning of fuels during oil processing and upgrading.

Environment Canada’s National Pollutant Release Inventory reports that upstream petroleum activities contribute to 21 per cent of the sulphur dioxide and 13 per cent of the nitrogen oxide in Canada.

• air quality management
  In 1999, industry participated in a Clean Air Strategic Alliance (CASA) study of potential acidification of soil and water systems in Alberta. The study concluded there were no areas in Alberta receiving harmful levels of acid deposition. Through CASA, industry has also helped to develop a provincial management framework to maintain acidifying emissions at environmentally safe levels.
  
  Industry is a founding member of the Cumulative Environmental Management Association, an organization based in Fort McMurray, Alberta. This organization brings together stakeholders and ideas to tackle regional issues, including the impact of sulphur dioxide and nitrogen oxide emissions on soil acidification.
  
  
• sulphur recovery
  About one third of Western Canada’s natural gas production is sour gas containing hydrogen sulphide. Most of this sour gas is processed at special sulphur recovery plants using catalysts to extract elemental sulphur for sale to fertilizer manufacturers and other industries. Sulphur recovery at sour gas plants has increased to 98.9 per cent from 95 per cent in the 1970s. Sulphur emissions from larger sour gas plants decreased from 273,000 tonnes each year in 1972 to 64,000 tonnes in 2002. This improvement has occurred despite increasing growth in sour gas production in Western Canada.
  
  Oilsands mining projects near Fort McMurray, Alberta also include sulphur recovery as part of their facilities. Upgraders remove most of the sulphur from bitumen by converting it into elemental sulphur or retaining it in a coke byproduct. The remaining sulphur is released into the atmosphere as sulphur dioxide.
  
  
• flare improvements
  Sulphur dioxide is emitted by flaring at oil batteries and gas plants where volumes and concentrations of sulphur dioxide are small. Sulphur recovery guidelines require that even some small batteries divert gas to processing plants. Reductions in flaring also reduce releases of sulphur dioxide.
  
  Oilsands developers also capture emissions of sulphur dioxide and hydrocarbons formerly released into the atmosphere or flared, burning the gases in high efficiency boilers equipped with pollution controls.
  
  
• operating efficiencies
  Oil and gas producers, such as in Alberta’s oilsands industry, optimize boiler operations to improve fuel efficiencies, thereby lowering NOx emissions. Emissions are also reduced through the use of improved combustion equipment, including low NOx burners.