The agency will promote the firm as 'ethical manufacturers using genuinely sustainable options'.
It was appointed to the account without a pitch. Stan director Andrew Crosbie will run the business.
'The biofuels industry has been suffering from a backlash over the past few months. It has come across a lot of criticism for the environmental damage biofuels can cause. We have been brought on board to promote the positive environmental benefits that they can create,' said Crosbie.
ESL was established in 1999 and is one of the UK's first commercial biodiesel manufacturers.
Last month the anti-biofuels lobby announced is was planning a summer of activism following government legislation (PRWeek, 18 April).