Last year, FWB helped the management team to recruit an Operations Director to support the growth and expansion of the business.
The companies gave no details of the transaction, but a person familiar with the deal said John Swire & Sons (Green Investments) had paid about £80m for Argent. The Scottish group was profitable, debt free and had turnover of more than £50m last year.
The deal marks the exit from Argent of Souter Investments, a private company controlled by the family of Brian Souter, founder of transport group Stagecoach.
Argent, which employs 70 people, makes diesel from used cooking oil from the food industry, tallow from the meat industry and grease from sewers. The company said it has been operating at its output capacity of 50m litres a year amid growing demand for “green” fuels.
Producing biodiesel from recycled waste is far less controversial than relying on specially grown crops, an approach that critics say is inefficient and puts pressure on farmland.
“We believe [Argent] can grow and prosper not only within the UK but also overseas, in particular in Asian markets with which Swire Group companies are familiar,” said Barnaby Swire of London-headquartered John Swire & Sons.
Swire will continue to operate Argent as a separate business.
Argent, which was established in 2001, uses technology developed by BDI-BioEnergy International of Austria to purify waste oils.