Alcoa is moving to increase the nameplate capacity of its biggest alumina refinery at Pinjarra by almost 20 per cent, according to an application lodged with the environmental watchdog.

Alcoa has applied to the Environmental Protection Authority for approval to shift bottlenecks at the Pinjarra refinery to lift its capacity to five million tonnes of alumina a year, the maximum allowed under current environmental approvals.

The nameplate capacity of the Pinjarra refinery is 4.2mtpa, but it produced 4.5mtpa in 2018 according to 40 per cent owner Alumina.

An Alcoa spokeswoman said it was in the early phase of assessing the expansion and had not made an investment decision.

Alcoa declined to say if its decision would be influenced by recent claims that Federal Labor’s plans to cut carbon emissions could savage the State’s alumina sector.

“Alcoa considers a range of factors when evaluating investment opportunities,” the spokeswoman said.

The application stated that construction was planned to start in the June quarter of 2020 with operations commencing in the December quarter of 2021.

Alcoa and Alumina also own the 2.6mtpa Wagerup and 2mpta Kwinana refineries.

Image: Aluminia Refinery, Getty Images