The study by University of Bath found that different varieties of coffee, including Robusta and Arabica, have reasonably standard composition and relevant physical properties of fuel, suggesting that all coffee waste could be a "viable" way of producing biodiesel.
Chris Chuck, Whorrod research fellow at the university, said that around eight million tonnes of coffee are produced globally each year, and ground waste coffee contains up to 20 percent oil per unit weight.
This oil also has similar properties to current feedstocks used to make biofuels. But, while those are cultivated specifically to produce fuel, spent coffee grounds are waste, and there's a real potential to produce a truly sustainable second-generation biofuel using these, he added.
Companies such as London-based bio-bean already produce biodiesel and biomass pellets from waste coffee grounds.
Rhodri Jenkins, a PhD student in sustainable chemical technologies and first author of the study, said that based on the estimates, a small coffee shop would produce around 10kg of coffee waste per day, which could be used to produce around two litres of biofuel.
If the large amounts of waste produced by the coffee bean roasting industry are scaled up, coffee biodiesel has great potential as a sustainable fuel source, Jenkins added.
The research is published in Energy Fuels.