40. What if there is a leak of CO2 from a pipeline?

A leak from a CO2 pipeline is highly unlikely and even tiny leaks can be very quickly detected and dealt with. However, if a leak were to occur it could have several effects. A slow leak over time would in most cases be dispersed without health effects, provided there were no other substances in the pipeline that could be dangerous. However, because CO2 is heavier than air, a slow leak of CO2 into a low lying area in exceptional circumstances (like a day when there was no wind or air movement) could result in CO2 accumulating in one spot to a dangerous level, leading to a potential hazard. However, such a leak would be very quickly detected and dealt with due to a decrease of pressure in the pipe.

A major pipeline rupture (caused by a puncture, for example) might cause an initial explosion because the pipeline is under pressure; persons close to the rupture could be injured by an explosion. Injury from the cold temperatures caused by the expansion of compressed CO2 is also possible.

People who are stuck in a small space with concentrated CO2 vapor would need supplemental oxygen, but under most weather conditions, the plume of emerging CO2 would be very visible, because water vapor in the air would condense in the suddenly cold conditions. The CO2 would emerge from the pipeline in a flow that would quickly turn solid once it came into contact with the air. This escaping CO2 would dissipate slowly as the solid turned to gas. CO2 is heavier than the air around it, and so it could collect in low lying areas, but CO2 also dissipates easily to non-toxic levels in even minor winds.

Figure 29. The CO2 pipeline from Beulah, North Dakota, to southern Saskatchewan is buried more than six feet deep to minimise the potential for ruptures. (Photograph courtesy of Dakota Gasification Company)

Most importantly, all modern pipelines (including those that supply CO2 from North Dakota to Saskatchewan in the WMP) are monitored with advanced computer systems that sense pressure reductions in the pipeline and are able to stop the flow of gas very quickly at various points along the route should any potential pressure drop occur. There has never been an injury incurred, nor leak of CO2, from the pipeline that feeds the Weyburn and Midale oilfields, and piping CO2 across long distances is commonplace in North America.