Edmonton Journal. Canadian Natural Resources (CNRL), an independent crude oil and natural gas producer, is applying a technique at its Horizon oil sands plant that uses CO2 to change the water chemistry of the tailings, resulting in accelerated settling and greatly reduced water use.

Since the system became fully operational for all tailings this winter “the amount of water we are withdrawing is only 13 to 14 per cent of what we were expected to draw from the river for our process on a daily basis,” CNRL president Steve Laut told The Journal. Using CO2, tailings silt separates much faster “and we are able to get that water back into the system, so we are recycling almost all our water,” Laut said.

CNRL plans to build a plant to capture its CO2 as a gas and inject that into the tailings, but until then the firm is bringing it from Fort Saskatchewan as a liquid in up to five tanker truckloads a day.

CNRL says that the CO2 is sequestered in the clay as it settles out in the pond at rates of between 50 and 100 percent. Studies are continuing to obtain more precise information on these rates.

The process is based on research from the federal CanmetENERGY lab in Devon, Canada.