A research team at Centre for Sustainable Chemical Technologies,University of Bath has created a new biofuel using waste coffee grounds which could be a potential source of fuel for powering vehicles on roads.
The team extracted the oil from coffee grounds by soaking them in an organic solvent and transforming the coffee grounds into biodiesel though a process called transesterification.
The biofuel was extracted from ground coffee produced in 20 different geographical locations. The study found that different types of coffee, including Arabica and Robusta have different fuel properties depending on the locations from which coffee was produced.
"Around 8 million tonnes of coffee are produced globally each year and ground waste coffee contains up to 20 per cent oil per unit weight ," explained Chris Chuck, Whorrod Research Fellow from Department of Chemical Engineering at University of Bath, in a news release.
"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. Using these, there's a real potential to produce a truly sustainable second-generation biofuel ," added Chuck.
The oil extracted from coffee was found to have a reasonably standard composition and a small variation in the relevant physical properties of the fuels. It is estimated that waste produced from the average coffee shop is about 22lb every day and was found to generate about two litres of biofuel.
Yields and properties of biodiesel can differ depending on the growth conditions of current biodiesel feedstocks, which sometimes cause them to fall out of specification while the uniformity across the board for the coffee biodiesel fuel is good news for biofuel producers and users according to Chuck.
Though the researchers believe that the biodiesel would be a small amount to fuel up cars, it could be produced in a small scale by coffee shops to fuel their cars for delivery purposes. Some firms such as London-based bio-bean already produce biodiesel and biomass from waste coffee grounds.
"We estimate that a small coffee shop would produce around 10kg of coffee waste per day, which could be used to produce around 2 litres of biofuel. There is also a large amount of waste produced by the coffee bean roasting industry, with defective beans being thrown away. If scaled up, we think coffee biodiesel has great potential as a sustainable fuel source ," said Rhodri Jenkins, the lead author of the study and a PhD student in Sustainable Chemical Technologies.
The researchers are also looking for using other types of food waste to make biofuels and hope to publish their findings later this year.
The details of the study have been published in the ACS journal Energy and Fuels.