Vale said the funds will be used to acquire a minority stake in the company, and promote the technology under its "New Pact with Society" net-zero carbon mining initative.

Boston Metal, an MIT spin-off that gained early backing from Bill Gates' Breakthrough Energy Ventures fund, is developing a Molten Oxide Electrolysis (MOE) technology, which reduces metal oxides such as iron ore with the use of electricity.

"We are excited with our investment in Boston Metal - it is an important stepping stone to the development of our portfolio of innovative technologies to provide decarbonization solutions," said Rogério Nogueira, Vale's marketing director.

The Vale funding comes after the company raised US$50 million last month in a Series B funding round led by Piva Capital, BHP Ventures, and Devonshire Investors, the private investment firm affiliated with FMR, the parent company of Fidelity Investments.

MOE technology uses electricity to transform metals from a raw oxide form into high-purity molten metal products, facilitating CO2 emissions-free steel production from a wide array of iron ores in a potentially more efficient, less costly and more sustainable approach.

"Boston Metal's mission is to deliver emissions-free steel at global scale," said Tadeu Carneiro, Chairman and CEO of Boston Metal. "Iron ore and clean electricity are the primary inputs into the MOE process and will heavily influence the design of our technology and our strategy. We are thrilled to add Vale and BHP, two of the largest iron ore companies, and Energy Impact Partners, a leading energy transition investor, to our world-class syndicate of investors and partners."

Last May, Brazilian niobium supplier CBMM held trials of MOE at its plant in Araxá.

Boston Metal plans to produce metals, partner with companies, and also license its MOE to existing metals makers.