The country's top refiner Indian Oil Corp (IOC) and other refiners have invested billions of dollars in recent years to install delayed coker units to produce high-valued added products such as gasoline and liquefied petroleum gas.

The units produce petcoke as a byproduct, equivalent to 25-30 percent of a unit's capacity, which refiners sell to local industries. But after the Supreme Court imposed a ban on petcoke in New Delhi and three surrounding states from last month to fight pollution, refiners are having to rethink what they do with the fuel.

IOC supplied petcoke from some of its plants, mainly in northern India, to industries in Haryana, Rajasthan and Uttar Pradesh - the states where it is now banned. It is still producing petcoke but diverting it to regions where it is not banned, its chairman Sanjiv Singh said on Tuesday.

The oil ministry has also asked state refiners to consider setting up petcoke gasifiers, a government source said.

IOC is evaluating building a 2 million tonne per annum (mtpa) petcoke gasifier costing Rs 15,000 - Rs 20,000 crore ($2.3 bln-$3.1 bln) at its 300,000-barrel per day (bpd) Paradip refinery in eastern India, its chairman said.

Gas made from petcoke can be used internally in refineries and at petrochemical plants.

"Normally petcoke gasifiers are large and capital intensive. A possibility is that we can build one gasifier for two to three refineries," Singh said. IOC operates 11 refineries in India.

Reliance Industries, owner of the world's biggest oil refining complex, has set up petcoke gasifiers to produce gas for internal needs using 6.5 mtpa petcoke produced at its two refineries.