When Dutch brewer Heineken and British drinks group Diageo teamed up with a non-profit organisation to help African farmers grow sorghum, little did they realise that their social experiment would turn into a sustainable business.

Heineken and Diageo, which owns the stout brand Guinness, started work with Brussels-based European Co-operative for Rural Development more than a year ago on a five-year project to encourage farmers to produce sorghum in Ghana and Sierra Leone.