(Refiles NOV 3 story to add attribution to headline, no change to story text)

By Pratima Desai

LONDON (Reuters) -Glencore ( GLCNF ) is planning to close its Horne smelter, Canada's largest copper metal-producing operation, due to environmental issues and the millions of dollars needed to upgrade the facility, two sources with knowledge of the matter said.

The London-listed miner does not disclose copper metal production figures for its Canadian operation, but industry sources estimate annual output at more than 300,000 metric tons.

The closure of Horne would reinforce forecasts of global shortages partly due to supply disruptions including accidents at mines in Indonesia and Chile.

Expectations of deficits in coming years have buoyed copper prices, which hit a record $11,200 a ton on October 29.

"Glencore ( GLCNF ) is not currently considering the closure of the Horne smelter or CCR," a Glencore ( GLCNF ) spokesperson said in response to a Reuters request for comment.

Its Canadian copper operations include Horne and the Canadian Copper Refinery. Both are located in the province of Quebec. The two sites employ more than 1,000 workers, according to industry sources.

"Smelters currently face enormous pressures around the world, including significant financial, regulatory and operational pressure," Glencore's ( GLCNF ) spokesperson said.

"Horne and CCR are not exempt from this though both assets play an important role in the supply of critical raw materials for the North American market and abroad."

While both plants will be closed, as yet there is no date, according to the two sources, who said the operations require potentially more than $200 million to modernise.

"We are continuing to implement our emissions reduction plan by advancing studies and other works," Glencore's ( GLCNF ) spokesperson said. 

"We are also working closely with all stakeholders to map a path forward that preserves Horne's ongoing smelting operations in Canada. This includes a clear and predictable regulatory framework necessary to secure the appropriate investment."

LAWSUIT OVER ARSENIC EMISSIONS

The commodity trader is facing a lawsuit in Quebec's Superior Court from local people for Horne's arsenic emissions. The court said damages back to 2020 can be claimed.

Long-term exposure to arsenic can cause cancer.

Glencore's ( GLCNF ) plans to close Horne and CCR are not related to the case, but to the costs of making the operation environmentally safe, according to the two sources.

"Glencore Canada acknowledges the Superior Court's decision to authorise the class action lawsuit," Glencore's ( GLCNF ) spokesperson said in response to a Reuters request for comment on the lawsuit.

"As this is an ongoing legal matter that we are contesting in court, we won't be commenting publicly on the proceedings at this time. We are confident that the Horne Smelter's operations are safe for the public," Glencore ( GLCNF ) said.

Founded in 1927, the Horne smelter pioneered the recycling of electronic scrap in 1980.

Glencore ( GLCNF ) processes around 100,000 metric tons of discarded electronics annually to produce copper, nickel, cobalt, gold and silver, according to its website.

Horne also processes concentrate to make copper anode which is turned into cathode by CCR. Much of Glencore's ( GLCNF ) copper metal production in Canada goes to the United States which is a net importer.

Canada exported more than 150,000 tons of copper to the United States last year, accounting for some 17% of U.S. imports and ranking it second behind Chile which accounted for 70%.

Profits at custom smelters - those that buy copper concentrate on the open market - have dropped this year due to pressure on treatment charges from global shortages of concentrate due to mine disruptions.

Miners pay treatment and refining charges to smelters to process their concentrate into refined metal.

Treatment and refining charges have been negative on the spot market since last year meaning smelters have to pay miners for concentrate instead of being paid to process the feedstock into metal.

Glencore ( GLCNF ) sold its Pasar copper refinery in the Philippines, a custom smelter, earlier this year.