In his doctoral project Steven Wainaina has investigated a novel approach that transforms the food waste into high-value products that can be recycled to benefit society, and helps to preserve some of the natural resources.

A common way to manage food waste is to process it into biogas through a process known as anaerobic digestion with microorganisms. The end product of this process is called biogas.

“In my project we have used immersed membrane in bioreactors and modified the digestion process to obtain valuable organic acids, so called fatty acids, such as acetic acid, butyric acid and caproic acid, as the end products. These acids have a higher market value than biogas. Furthermore, this research demonstrated for the first time that the organic acids can be transformed into edible filamentous fungi, which can be used in the production of animal feed. The fatty acids also can be used in the production of bio plastics”, tells Steven Wainaina.

How will your research be of benefit for the society and/or the industry?

“The trend in food waste generation is expected to increase as the human population continues to increase. Innovative food waste management techniques are therefore critically needed. The results obtained in this research highlight a possible and promising alternative of recycling food waste.”

This project is an important contribution to ongoing research within anaerobic digestion technology. It proposes a unique way to enable the expansion of the possible outputs from anaerobic digestion facilities. Furthermore, it provides an important basis for further investigations that could lead to full-scale implementation. 

What would be the next step for your findings?

– The scale up of the production and separation of organic acids in membrane bioreactors is planned. Also, further research to optimize the conversion of organic acids into edible fungi is ongoing.

Title of the doctoral thesis: Developing a food waste-based volatile fatty acids platform using an immersed membrane bioreactor

Research area: Resource Recovery

The overall purpose of the project was to prove the concept of altering the anaerobic digestion of food waste from a biogas production process into a material recovery process.

This research aligns well with Sustainable Development Goal number 12 which aims to promote sustainable consumption and production, as well as the protection and management of natural resources.

Steven Wainaina publicly defended his thesis on 18 September at the Swedish Centre for Resource Recovery, University of Borås.

Main supervisor: Professor Mohammad Taherzadeh