By Simon Jessop

LONDON, Jan 21 (Reuters) - U.S. carbon accounting firm Gravity said it has won backing from Ansa Capital and the venture arm of fuel card company WEX WEX.N in a $13 million funding round as it looks to help energy-intensive companies track and reduce their emissions.

Countries across the world are increasingly asking companies to disclose their carbon emissions as part of efforts to curtail global warming and more boards are looking to make energy efficiency savings.

While various start-ups have sought to capture this demand, many require manual data entry that can be time consuming and costly, whereas Gravity is automated, Chief Executive and co-founder Saleh ElHattab said.

"Ultimately, behind every ton of emissions is a cost – whether it's energy spend, logistics investments, or purchased goods and services," ElHattab said in a statement.

"Gravity taps into the fact that these cost centers are already well-tracked and can be measured automatically, while connecting the task of reporting back to every company's core financial priorities of cost and risk mitigation."

New investors Communitas Capital and Buoyant Ventures joined in the Ansa-led Series A round with WEX Venture Capital. Existing investors Eclipse, Hanover, and Caffeinated Capital also took part.

The money will be used to expand Gravity's research and development efforts, as well as hire staff in the United States and European Union, it added.

"We believe Gravity will be instrumental in helping the largest emitters move beyond emissions calculation to actively managing their energy costs...on one convenient platform," said Ansa Co-Founder Marco DeMeireles, who will join Gravity's board.

(Reporting by Simon Jessop; Editing by Kirsten Donovan)

((simon.jessop@thomsonreuters.com; +44 (0) 207 542 5052; Reuters Messaging: Reuters Messaging: simon.jessop.thomsonreuters.com@reuters.net))