Air

Electric motors drive most of the pumps on liquid petroleum transmission pipelines in Canada. Diesel powered generators are used in only a few locations not served with high-voltage electric power or as emergency backup power supplies. As a result, liquids pipelines issue few direct emissions; those that occur are mostly the result of evaporative losses from above-ground storage tanks at bulk terminals.

Natural gas transmission companies compress the gas up to 100 times atmospheric pressure for pipeline transportation. Natural gas-fueled turbine engines, similar to the engines on large jet airplanes, drive most of the compressors on natural gas transmission pipelines in Canada. Electric motors or natural gas-powered conventional (reciprocating) engines are also used for compression.

Greenhouse gases

Direct emissions of carbon dioxide result mainly from the burning of natural gas, the main fuel source used by natural gas transmission pipelines. Also, methane (the primary component of natural gas) can escape as fugitive emissions from pipeline systems through small leaks in valves, fittings and other related equipment. Methane is also vented when pipelines must be emptied prior to construction and maintenance work or by system equipment that is designed to regulate pressure in order to maintain pipeline safety.

Indirect greenhouse gas emissions result from electricity consumed by pumps on pipelines carrying crude oil and other liquid petroleum products. The method used to generate the electricity that is consumed by these pumps has a significant impact upon the amount of indirect greenhouse gas emissions since coal fired electrical generation has a much higher greenhouse gas intensity than that produced by hydroelectric generation. The viscosity (resistance to flow) of the products transported also affects indirect emissions, as products such as heavy oil and bitumen require more electric power to transport, resulting in greater indirect emissions.

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