March 2, 2024

I, Science

The science magazine of Imperial College

Can a new process of converting ground coffee waste in to biodiesel create an economically viable alternative fuel?

It’s five o’clock in the afternoon. On a busy South London street, people are finally making their way home after a long day in the office. Imagine John, a local restaurant owner. He serves his last guest, then waits outside for the local waste collection service. Behind him he has placed two large bags of leftover coffee grounds ready for collection. But contrary to the usual process, the coffee waste does not end up in a nearby landfill. Instead, it will be collected along with more organic waste from other nearby businesses, and taken to a refinery where it will be transformed into biodiesel.

Dr. Vesna Najdanovic-Visak, at Lancaster university, is a lecturer in Technical Engineering and head researcher of this new technology. She explains how ecologically, using waste products has many advantages compared to conventional methods of producing biofuels: “Anything that you use in fuel production which doesn’t compete with crops grown for food, is better.” Using coffee grounds therefore presents itself as an even greener alternative: “It’s a question of sustainability and a moral question as well, since many people don’t have access to enough food.”

Along with these ecological advantages, the new system is economically viable as well. Although similar methods of using coffee grounds in biofuel production have been around for a while, they doesn’t seem to be efficient enough to become a mainstream alternative given nine million tonnes of coffee waste were still sent to landfills in 2014. Dr Najdanovic-Visak’s method proposes a shortcut to the refining process. Until now, a hexane solvent was used to allow oils in the coffee grounds to diffuse. In a second step these oils were combined with the reactant methanol to produce biodiesel under high temperatures.

These steps have now been changed. “Instead of first doing extraction and then conversion into biodiesel, we fused the steps to have them happening at the same time”, explains Najdanovic-Visak. This process, called in-situ transesterification, is not only saving time, but also chemical waste in the form of hexane. And with six tonnes of coffee grounds needed to produce one ton of biodiesel, this adds up to 720,000 tonnes of biodiesel, which could be produced every year from spent coffee grounds.

For business owners, the incentive doesn’t only lie in a convenient and cheap way to get rid of undesired waste. They can also contribute to a greener approach on a daily basis, starting with the coffee that we drink first thing in the morning.

Katharina Kropshofer is studying for an MSc in Science Communication at Imperial College London

Banner image: coffee bean heart, endlessbuta