As the planet adds another 2 billion inhabitants by 2040, natural gas and unconventional resources will play a key role in meeting a 35% increase in energy demands, according to ExxonMobil’s 2013 Outlook For Energy.

In the United States, increasing energy efficiency will blunt a large portion of the demand as the nation heads toward being a net energy exporter by the end of the decade, said William Colton, ExxonMobil vice president for corporate strategic planning. Colton spoke March 13 at Rice University’s Baker Institute Center for Energy Studies.

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