Alberta has committed to phase in a $50-per-tonne carbon tax after the federal government approved a major pipeline proposal to Canada's Pacific coast.

The Trudeau government on Tuesday approved Kinder Morgan Canada Inc.'s $6.8-billion Trans Mountain pipeline, which would nearly triple capacity on an existing line from Edmonton to Burnaby, B.C. to about 900,000 barrels per day.

In a statement, Premier Rachel Notley said the province would phase in the levy on carbon emissions in line with federal plan to tax emissions at $50 per tonne by 2022.

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Read more: Federal government approves Trans Mountain pipeline, Line 3 expansion

Ms. Notley had previously withheld support for the federal initiative pending approval of a pipeline to export growing oil sands production to overseas markets. A provincial tax of $20 per tonne on carbon emissions is set to take effect next year. That was set to rise to $30 by 2018.