Scientists at the University of Bath, UK have made biodiesel from coffee grounds, suggesting it could become a potential “local” alternative fuel source.

New research from the Centre for Sustainable Chemical Technologies and published in the ACS Journal Energy & Fuels showed that oil can be extracted from both fresh and waste coffee grounds by soaking them in an organic solvent, before being chemically transformed into biodiesel via a process called “transesterification”.

Dr Chris Chuck, Whorrod Research Fellow from the Department of Chemical Engineering at The University of Bath, said: “Around 8 million tonnes of coffee are produced globally each year and ground waste coffee contains up to 20% 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. Using these, there’s a real potential to produce a truly sustainable second-generation biofuel.

“The yields and properties of biodiesel can differ depending on the growth conditions of current biodiesel feedstocks, sometimes causing them to fall out of specification. The uniformity across the board for the coffee biodiesel fuel is good news for biofuel producers and users.” That means, he said, that coffee is actually a more stable, if smaller scale, alternative to current feedstock-based biodiesel.

The researchers suggest that while coffee biodiesel would be a relatively minor part of the energy mix, it could be produced on a small scale by coffee shop chains to fuel vehicles used for deliveries. These same delivery vehicles could be used to collect spent coffee grinds and take them to a central biodiesel production facility to be processed. 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: “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”.


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