5 July 2017
A Lancaster University student’s masters’ dissertation offers new commercial possibilities for turning waste coffee grounds into biofuel.

Like many students, Hong Kong born Yee-Lam (Florence) Lee loves to spend time in coffee shops.

While sipping her daily latte, Florence worried about what was happening to all the waste coffee grounds: it was the starting of a research project which could revolutionise the efficiency of biofuel production from coffee waste.

“I noticed those spent coffee grounds being discarded in bins, which end up in the landfill.

Since I had studied environmental science for several years, I had the concept of waste as a potential resource rather than a problem,” said Florence, who was looking for a dissertation topic for her MSc Environment and Development.

She did some initial research on the internet and discovered that a few businesses were using spent coffee grounds to make biofuels on a small scale.  Florence loved the idea of making sustainable biofuels, having done her undergraduate dissertation on air pollution from commercial diesel vehicles in Hong Kong.

Florence wondered if she could find a way to improve the process of turning coffee grounds into biodiesel to make it more commercially attractive.

“In 2014 more than nine million tonnes of spent coffee grounds were sent to landfill,” said Florence. “Purpose-grown feedstocks (used to extract oils) for biodiesels are controversial because of their cost and the demand they place on land and water. However, spent coffee grounds, which have a high calorific value, offer a good low-cost alternative feedstock.”

She came up with a proposal and sent it to academics in the Lancaster Environment Centre, among them Dr Alona Armstrong, who a forwarded it to Dr Vesna Najdanovic-Visak, a colleague in the Engineering Department.

Both academics are part of the cross disciplinary Energy Lancaster, and they decided to jointly supervise Florence’s dissertation project.

‘It was a fantastic opportunity to undertake some topical research, work with one of my Energy Lancaster colleagues and enable Florence to follow her passion.’ said Alona.

Alongside studying for her degree, Florence spent five months as a biofuel intern doing experiments in the chemical engineering laboratory, guided by Vesna and Alona.

She was working on ways to consolidate the existing multi-stage biofuel production process into one step - known as in-situ transesterification. This combines extraction of the oils from the spent coffee grounds and the conversion of it into coffee biodiesel.

In the traditional process, manufacturers extract the oil by mixing spent coffee grounds with hexane and cooking the mixture at 60°C for between 1-2 hours. The hexane is then evaporated to leave behind the oils. Methanol and a catalyst are then added to make biodiesel and a glycerol byproduct – which also needs separating.

Florence’s experiments showed that it is possible to combine the two processes, using just methanol and a catalyst, so removing the need for hexane altogether and saving on chemical waste.

The new process also significantly reduces the time needed to get the same yield to just ten minutes, offering big savings on energy costs. 

“Our method vastly reduces the time and cost needed to extract the oils for biofuel, making spent coffee grounds a much more commercially competitive source of fuel,” said Vesna. “A huge amount of spent coffee grounds, which are currently just being dumped in a landfill, could now be used to bring significant environmental benefits over diesel from fossil fuel sources.

“This research was driven by Florence’s passion for coffee. She has performed very precise experimental work in my laboratory. It was a true pleasure to supervise such a dedicated and creative student.”

The process has the potential to enable 720,000 tonnes of biodiesel to be produced each year from spent coffee grounds. The work has now been published in the Journal of Environmental Chemical Engineering in a paper called ‘Kinetics of extraction and in situ transesterification of oils from spent coffee grounds’,

As well as the gaining kudos from having her research published in an international journal, Florence got the chance to represent Lancaster University at the Student Green Challenge conference in Copenhagen.

She graduated with a merit, and is now working as a Research Officer for a  think tank, the Hong Kong Sustainable Development Research Institute, focusing on multiple research areas, including:  ‘Silver Hair’ industry; middle-class economy; municipal solid waste management; constitutional development and public administration.

Learn more about studying for a masters degree at Lancaster University’s Graduate School for the Environment.