KHOBAR: Saudi Aramco has signed agreements (ECA) with a Japanese-Saudi consortium to build and operate cogeneration power plants, as the state-owned giant tries to make its operations more energy efficient, it said on Wednesday.

Cogeneration saves energy and lowers carbon dioxide emissions by channeling excess heat from electricity generation for other purposes such as domestic heating or industrial processes.

Saudi Aramco signed the agreements with Marubeni Corp and JGC Corp of Japan and Saudi Aljomaih Energy & Water Co.

Once online in 2016, the plants will provide 900 megawatts of power and 1,500 tonnes of steam per hour for Aramco industrial facilities at Abqaiq, Hawiyah and Ras Tanura.

Abqaiq is home to the world's largest oil processing plant, Hawiyah has a large gas plant and Ras Tanura is the site of Aramco's first refinery and the largest in the Middle East.

Aramco, which did not state the value of the agreements, said it would hold a 50-percent stake in the plants which Marubeni, JGC and Aljomaih would build and operate for 20 years.

An industry source said Marubeni would have 25 percent, JGC 15 percent and Aljomaih 10 percent stakes in the new power stations.