Oslo-listed Klaveness Combination Carriers (KCC) has clinched a long-term deal to carry caustic soda for Australian mining and metals company South32.

The combination carrier owner has signed a six-year contract of affreightment (COA) for shipments on its Cleanbu-class vessels from South32's Worsley Alumina refinery in Western Australia.

No financial details have been released, but the companies said the deal establishes a framework for how they will work together to deliver further reductions in carbon emissions in the trade.

The sustainability element of the COA includes detailed CO2 emissions reporting and the establishing of trajectories for annual CO2 reductions targets.

The two sides also stated an ambition to jointly establish a pathway towards future zero-emission freight.

KCC and other Klaveness group companies have serviced Worsley Alumina with four generations of combination carriers on a continued basis for more than 30 years.

Engebret Dahm, KCC's chief executive, said the agreement marked another important milestone in the long-standing relationship with South32.

Generational challenge

"In this next era of our relationship, together we will address the main challenge of our generation: climate change," he said.

"We have jointly set ambitions to considerably reduce shipping carbon emissions through building on KCC’s low-carbon caustic soda shipping solution, which already today provides South32 with a 30% to 40% lower carbon footprint than competing tanker vessels."

Brendan Harris, chief human resources and commercial officer at South32, said such partnerships contribute to the decarbonisation of its value chain and promote the responsible production of commodities needed in a low-carbon world.

The miner is committed to achieving net-zero operational carbon emissions by 2050.

By 2035, it wants to cut these emissions in half.

Perth-based South32 was spun out of BHP Billiton in 2015.

Last August, KCC sealed its longest COA at that point for carrying refined products with its midsize vessels.

The one-year contract was agreed with an unnamed "major international charterer" and can be extended by up to two years.

KCC’s Cleanbu fleet of eight 82,500-dwt vessels is capable of transporting both refined products and dry bulk cargoes.

The company estimated the deal translated to 12 to 18 months of employment time for one of the Cleanbu ships.