Report - Agence canadienne d'évaluation environnementale

Chapter 5 Assessing the risks related to the
project
In this chapter, the Panel addresses the potential risks associated with the
construction of the LNG terminal and related infrastructures. The analysis was guided
by the concerns, opinions and views expressed during the public hearings, as well as
by the assessment and the criteria used by the proponent in his studies. The risks
related to the project concern three aspects: LNG tanker navigation in the seaway; the
project’s land facilities, including berthed LNG tankers; and the proposed pipeline.
The properties and related hazards of liquefied
natural gas
Chemically, LNG is essentially made up of methane in a proportion that can vary
between 85 and 95 percent on a volume basis, depending on its origin. Liquefied by
cooling at -160 ºC, and reduced to 1/600 th of its original volume in this state, with a
slightly lower density than water, LNG becomes easily storable and transportable
under close to atmospheric pressure conditions. It is clear, transparent, odourless,
non-corrosive and non-toxic.
The potential hazards of LNG are mainly linked to its very low temperature and the
cryogenic aspects that stem from it. Specifically, these hazards concern, first and
foremost, employees working in close proximity to the liquefaction and tanker loading
areas, unloading areas or storage and LNG regasification equipment facilities. There
are also risks of thermal embrittlement and damage caused to the component
materials of the facilities which are not meant to come into direct contact with the
LNG.
LNG is only flammable in its gaseous state, as is the case for other hydrocarbons.
Consequently, in the presence of an ignition source, or if the temperature is
sufficiently high to reach the point of auto-ignition, LNG will ignite, with a combustion
rate that is relatively slow 1 . Natural gas has an auto-ignition temperature of 540 ºC, a
higher temperature compared to diesel (260 ºC) and to premium grade gasoline
1. The minimal energy required to ignite LNG vapours is 0.29 millijoule (mJ). This would justify the conclusion that it
would be unlikely that LNG clouds could travel and spread over great distances without quickly igniting close to
their sources. To compare, the electric energy freed by walking on a carpet or by combing hair is in the order of
10 mJ, or 35 times the minimal energy required to ignite LNG vapours [On-line: http://archives1.iomosaic.com/
whitepapers/Managing%20LNG%20Risks.pdf].
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