Hindustan Zinc Ltd. is preparing for a major capex programme as the Vedanta Ltd.-owned company aims to double its zinc output in the next three to four years.“I have already started an RFQ (request for quotation) inviting tenders... global tender for mining, mining designers and mining operators to work with me to see how 1 million tonne production can become 2 million,” Arun Misra, chief executive officer of India's largest zinc producer, told NDTV Profit in an exclusive interview at the Dariba Smelter Complex in Rajasthan.The project cost for this expansion would range between Rs 15,000 crore and Rs 18,000 crore and be spread over three to four years, Misra said, adding that the detailed plan for the same needs to go to the board for approval.The new capex also aims to bump up the company's silver production to 2,000 tonnes per year. The metric currently stands at 750 tonnes, and Hindustan Zinc is already targeting 1,000 tonnes of production.As part of its ongoing annual capex, the company is looking at increasing its zinc production to 1.5 million tonnes in a phased manner.Electrification Of MiningIn addition, the miner is looking to electrify all its mining equipment.“We're also introducing battery-operated vehicles and electric vehicles in the underground mines,” Misra said. “We have about 900 mining vehicles operating in eight underground mines. We have kept a budget of $1 billion to replace them over time.”The company has already introduced a set of four or five pieces of autonomous mining equipment in the Sindesar Khurd Mine —a first for an underground mine in India and a first in Asia.Lower Production CostsThe move to renewable energy and electrification of mining will open up newer markets for Hindustan Zinc, where it can supply green zinc to the steel industry, which needs to comply with Scope 3 compliance as per the Paris Agreement. Steelmakers are among the largest greenhouse gas emitters globally, and zinc is widely used in the alloy's production. “The green zinc will be sold at a premium and could fetch a premium of $30–40 per tonne,” said Misra.Government Stake SaleThe government is expected to restart the process of offer-for-sale to offload its stake in Hindustan Zinc, said Misra. It's working with the idea of restarting roadshows and coming out with tranches of shares to be offloaded in the market.The demerger is unlikely to impact the OFS process; it will provide investors with value-unlocking opportunities in the zinc and silver business, Misra said while referring to the company's recent plan to spin off its business into two. The demerger is expected to unlock $3–4 billion in value, he said, adding that approval for the same is expected by April–May this year.Hindustan Zinc's Two-Way Spinoff On The Cards, Says Chairperson — Exclusive