RIYADH - Air Liquide Arabia (ALAR) on Tuesday began pumping hydrogen through its $400 million pipeline network in Saudi Arabia's Red Sea city of Yanbu and will supply a Saudi Aramco refinery as the kingdom seeks to shift towards cleaner fuel.

Pressure has mounted on the world's biggest fossil fuel producers to reduce their carbon emissions as concern mounts among policy-makers, investors and the general public about their impact on global warming.

Many in industry are turning to hydrogen gas, which can be used to fuel vehicles and as a means to store green energy, as part of the solution.

The Saudi Aramco Mobil Refinery (SAMREF), a joint venture between oil giant Saudi Aramco and a subsidiary of U.S. oil major ExxonMobil, will be the first company to use the Yanbu hydrogen grid, Francois-Xavier Haulle, ALAR's general manager, told Reuters by telephone.

His company, a joint venture between France's Air Liquide and Saudi Arabia's TAQA, 45.7% owned by the kingdom's sovereign wealth fund (PIF), plans to provide hydrogen (H2) to three other clients in 2020, he said.

Saudi Arabia, the world's largest crude oil exporter, told the United Nations in 2015 it would reduce expected emissions by up to 130 million tonnes a year by 2030. It did not give detail of its current emissions.

"H2 is critical to a clean, secure and affordable energy future in the kingdom. It can decarbonise a range of sectors, including long-haul transport and chemicals," Haulle said.

Haulle said his company plans to add more capacity to its hydrogen grid in Saudi Arabia, located on both the Red Sea and the Gulf coasts, from the current 200,000 normal meter cubed per hour (Nm3/hr), a measure of gas flow based on standard atmospheric conditions, at each site.

(Reporting by Marwa Rashad; Editing by Barbara Lewis) ((marwa.rashad@thomsonreuters.com; +966114868476; Reuters Messaging: marwa.rashad.thomsonreuters.com@reuters.net))