Primary aluminium emits on average 16.5 tonnes of CO2 per tonne of metal, according the International Aluminium Institute, based on 2019 data, making it one of the most carbon-intensive segments of the metals industry.

Below are lower-carbon aluminium brands by the major producers.

* ALCOA

ECOLUM - Primary aluminium with a total carbon footprint of under 4 tonnes of CO2, including bauxite mining and refining.

ECODURA - Aluminium billet made with minimum of 50% recycled content, lowering energy usage by 95%.

* NORSK HYDRO

REDUXA - Primary aluminium with carbon content below 4 tonnes of CO2 per tonne of metal, including emissions from bauxite mining and making products such as alloyed metal.

CIRCAL - Recycled metal with a minimum of 75% used aluminium and a footprint of less than 2.3 tonnes of CO2.

* RIO TINTO

RENEWAL - Primary metal with CO2 emissions of 4 tonnes or less of CO2 per tonne of metal.

* RUSAL

ALLOW - Primary metal with a footprint of less than 4 tonnes of CO2, based on direct and indirect smelter emissions only.

* ALCOA/RIO TINTO JOINT VENTURE

ELYSIS - Joint venture between the two groups to commercialise a new technology by 2024 to produce carbon-free aluminium, using a ceramic anode and emitting only oxygen.

(Reporting by Eric Onstad; Editing by Jan Harvey)