Two Aston University researchers have produced high-quality biodiesel after “feeding” and developing microalgae on leftover coffee grounds.

Dr. Vesna Najdanovic, Senior Lecturer in Chemical Engineering, and Dr. Jiawei Wang were part of a research group that grew algae, which was later processed into fuel.

In the UK alone, around 98 million cups of coffee are consumed in one day, which contributes to a huge amount of spent coffee grounds that are processed as general waste—usually ending up in incineration or landfill.

But, the scientists discovered that spent coffee grounds offer nutrients to feed and a structure to grow microalgae (Chlorella vulgaris sp.).

Consequently, they could extract superior biodiesel that creates good engine performance and low emissions and meets European and US specifications.

The study was featured in the November 2022 Renewable and Sustainable Energy Reviews issue.

Until now, algae has been developed on materials like nylon and polyurethane foam that do not offer any nutrients. The researchers, however, discovered that microalgal cells could grow on the leftover coffee with no need for any other external nutrients.

They also discovered that exposure of the algae to light for 20 hours a day and dark for four hours a day produced the finest quality of biodiesel.

“This is a breakthrough in the microalgal cultivation system. Biodiesel from microalgae attached to spent coffee grounds could be an ideal choice for new feedstock commercialization, avoiding competition with food crops. Furthermore, using this new feedstock could decrease the cutting down of palm trees to extract oil to produce biofuel. This has led to continuous deforestation and increased greenhouse gas emissions in Southeast Asia.”

—— Dr. Najdanovic, Aston University

The study was a great example of teamwork, with colleagues from Malaysia, Thailand, Egypt, South Africa, and India. 2020-21 Global Challenges Research Fund (GCRF) block grant funded by the UK Research and Innovation (Aston University) supported their research.