The London Metal Exchange (LME) has added standards for small-scale mining to its digital sustainability register and pledged to achieve net-zero emissions for its own operations by 2040, it said on Monday.

The 145-year-old exchange launched LMEpassport last year so miners could store sustainability credentials, such as carbon footprints and social impacts, plus other characteristics like purity, for metals trading on its platform.

The register is part of an initiative by the world's biggest market for industrial metals to clean up global supply chains and delist brands that are not responsibly sourced.

Nearly half of the LME's 443 brands have added disclosures to LMEpassport, the exchange said in a statement at the start of industry gathering LME Week.

LMEpassport will now also include standards regarding artisanal mining, which is an important source of income for about 150-million people worldwide, but it can cause environmental damage and include child labour.

"Artisanal mining is happening and excluding it from the legitimate supply chain isn't helpful for those people," said Georgina Hallett, LME chief sustainability officer.

"If we can provide proper due diligence, robust processes, then we can genuinely improve things."

Initially, the LME standards will focus on the Democratic Republic of Congo, which accounts for the bulk of global cobalt output, of which up to 35% is mined by small-scale miners, according to industry group the Cobalt Institute.

The LME also announced on Monday that it will cut its own carbon emissions to net zero by 2040.

The exchange will develop a full reduction target and roadmap, which will be submitted to a third party for validation within 24 months, it added.

The LME's owner, Hong Kong Exchanges and Clearing, said in November last year it was joining a global coalition to support a transition to lower carbon, adding that it planned to achieve a net-zero target by 2050 or earlier.