The unit has a capacity of 105,000 barrels per day (bpd) of low sulfur diesel, with sulphur content of less than 10 parts per million (ppm), Aramco said in an e-mailed statement.

The Ras Tanura refinery is Aramco’s first refinery and the Middle East largest with a crude processing capacity of 550,000 bpd.

It produces naphtha, kerosene, diesel, liquified petroleum gas (LPG) and fuel oil.

Aramco has started to upgrade some of its refineries to comply with environmental standards.

It has launched last year a clean diesel unit at its 305,000 bpd refinery jointly owned by Royal Dutch Shell in Jubail and plans to complete in 2013 another clean fuel project at its 400,000 joint refinery in Yanbu with Exxon Mobil.