UPDATE 1-India's top copper smelter stays shut until at least May 14
* Local pollution board may appeal if smelter re-opened
* Copper imports to India rising - adviser
* May push copper concentrate processing fees even higher
NEW DELHI, May 8 (Reuters) - India's biggest copper smelter will stay shut until at least May 14 when a court will review an environmental case again, prolonging a six-week shutdown which is squeezing local supplies and boosting copper concentrate processing fees in Asia.
The Sterlite Industries' plant, which meets half of India's copper demand, was closed on March 30 after residents complained of emissions that led to breathing problems.
Justice Swatanter Kumar of the National Green Tribunal, a special fast-track environmental court, said on Wednesday an expert panel's report had to be given to all parties and set the next hearing for May 14.
The closure of the smelter, which uses imported concentrates, has pushed about 3,000 tonnes per day of concentrates onto the market.
The local environment authority said it might appeal to the Supreme Court if this court decides the plant can re-open.
"Based on the judgment, we may file an appeal with the Supreme Court," said Abdul Saleem, a lawyer for the Tamil Nadu Pollution Control Board.
In a separate case, India's top court last month fined Sterlite about $18 million for breaking environmental laws at the smelter.
The plant produces 30,000 tonnes of refined copper a month - or more than half of India's total production - and nearly half of the output goes to China.
"The closure is already having an impact, physical (copper) supplies are getting tight, and therefore imports into India are positively up," said Sandeep Daga, director at Regsus Consulting Pvt. Ltd. "Even if the plant starts, it will another 2-3 weeks to re-start production."
India's annual copper consumption was about 610,000 tonnes for the year ending March 31, according to government data. Most of its copper exports go to China, the world's biggest consumer of the metal, which used up around 9 million tonnes last year.
"Copper premiums are likely to remain high and could even possibly move up marginally as the plant will remain shut," said a Singapore-based metals trader.
"As of now there is not much of a copper cathode requirement from India but the longer the plant remains closed more and more and people will start looking to cover some of their requirement through imports," the trader added.
Cashing in on regional oversupply after the Sterlite closure, smelters across Asia have been charging the highest fees in five months to process concentrates.
"The impact of Sterlite's closure is that spot shipments have increased in Asia," said a trader at an international firm.
Spot concentrate was trading at treatment and refining charges of about $80 per tonne and 8 cents a pound to China, up by a third from $60 and 6 cents before the closure, added the trader.
The charges are paid by sellers of copper concentrates to smelters for converting the raw material into metal and then deducted from the sale price, based on London Metal Exchange copper prices .
Sterlite, a unit of London-listed resources conglomerate Vedanta Resources Plc, controlled by billionaire Anil Agarwal, has been awaiting clearances to double the capacity of the smelter to 800,000 tonnes a year.
The smelter in the coastal town of Tuticorin near the southern tip of India has long been the target of protesters and politicians who say it is a risk to the local fishing industry.