Definitions

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Definitions

Sulphur Dioxide (SO2)

Sulphur dioxide emissions result from the conversion of sulphur, found naturally in fossil fuels, into sulphur dioxide. Sulphur dioxide has two main environmental effects: it is a contributor to downwind acid rain and it is a contributor to fine particulate/smog.

Nitrogen Oxides (NOx)

Nitrogen Oxide emissions are produced as part of the complex combustion chemistry that occurs in a boiler. Basically, the nitrogen and oxygen present in air are broken apart and combined in different combinations under the high temperature conditions in the boiler. Nitrogen Oxides are a contributor to acid rain and smog and also play a role in reducing the earth’s ozone layer.

Carbon Dioxide (CO2)


Carbon dioxide is produced during the combustion of carbon found in fossil fuels. The combustion of carbon is one of the key sources of energy in fossil fuels but carbon dioxide is generated as a by-product. Currently, there are no commercially viable ways to capture carbon dioxide from fossil fuel generating plants. Technologies are under development but are not mature at the moment. Right now, the only way to reduce carbon dioxide emissions is to use less fuel through efficiency measures, move towards lower carbon fuels (natural gas produces less than coal) or produce more electricity using renewable energy sources such as hydro, wind, solar, etc.
Carbon dioxide is one of six greenhouse gases that are being targeted by international protocols to reduce the impacts of global warming/climate change. The main effect of greenhouse gases is to trap the earth’s heat within the atmosphere and to increase the global temperature. Global warming happens naturally as water vapour is actually the most prevalent greenhouse gas and without it the earth would be too cold to sustain life. However, human activity has added incremental greenhouse gases into the atmosphere that are expected to increase global temperatures.

Greenhouse Gases (GHG)


The Mandatory Greenhouse Gas (GHG) reporting program requires emitters of a specific size to report emissions of the six classes of greenhouse gases that are identified in the Kyoto Protocol. Of these six GHGs, four result from NSPI’s operations. They are:
  • Carbon Dioxide (CO2) resulting from combustion of carbon found in fossil fuels
  • Methane (CH4) resulting from small amounts of methane being emitted from the stacks of natural gas-fired plants such as Tufts Cove
  • Nitrous Oxide (NO2) which is created in lower temperature combustion systems such as Point Aconi
  • Sulphur Hexafluoride (SF6) which is an insulating gas that can leak from electrical equipment
These gases trap heat to different degrees. This means that an equal amount of these gases will retain different amounts of heat. To allow comparison and to determine the climate change impact of these gases, GHG emissions are reported as ‘equivalent CO2’ – which is known as CO2e. This is done through the use of multiplier factors known as “Global Warming Potentials” where each of these gases can be translated and reported as equivalent CO2.

The global warming potentials for the four GHGs NSPI reports are:
  • Carbon Dioxide = 1 (since all GHGs are reported as if they were CO2)
  • Methane = 25 (1 tonne of methane gas is equivalent to 25 tonnes of CO2)
  • Nitrous Oxides = 298 (1 tonne of Nitrous Oxides is equivalent to 298 tonnes of CO2)
  • Sulphur Hexafluoride = 22,800 (1 tonne of Sulphur Hexafluoride is equivalent to 22,800 tonnes of CO2)
  • (Source: “Climate Change 2007: the Physical Science Basis”,
  • Intergovernmental Panel on Climate Change – 100 year global warming potentials)

Mercury (Hg)


Mercury (Hg) emissions result from the combustion of naturally occurring mercury found in fossil fuels. However, the chemistry is complex and mercury can be found in many forms – some of which are easier to remove from the flue gas stream than others. Mercury is a pollutant that with high exposure can cause neurological damage and development problems in animals and humans.