LONDON, Jan 19 (Reuters) - The world's biggest bond investor, PIMCO, said on Thursday it had opened its first ethical debt investment fund in Europe, the Middle East and Africa (EMEA).

The fund will invest in a range of sovereign and investment-grade corporate bonds from around the world, favouring issuers with strong environmental, social and governance (ESG) credentials.

PIMCO said it had also enhanced two socially responsible funds in the United States to incorporate a wider range of ESG considerations.

"For many investors, screening out undesirable investment categories isn't enough anymore; they want to use their investments to promote change in the world," said Andrew Balls, PIMCO's bonds CIO.

The volume of "green bonds", where proceeds are earmarked specifically for environmental projects, nearly doubled in 2016 amid signs that this niche market could in coming years make a bigger contribution to the trillions of dollars needed to tackle climate change.

(Reporting by John Geddie, editing by Larry King) ((John.Geddie@thomsonreuters.com; +44 20 7542 3486; Reuters Messaging: john.geddie.thomsonreuters.com@reuters.net))