The combustion of fossil fuels produces large amounts of dilute CO₂ that is continuously released to the atmosphere. During her PhD studies, Madhuni Madhushika Wijesooriya investigated how microorganisms can convert captured dilute carbon dioxide into renewable methane that can be used as fuel (“renewable natural gas”). Studying the process of Bio-Integrated Carbon Capture and Utilization (BICCU), the research focused on how liquid chemical agents used to capture carbon dioxide affect these microbes and the efficiency of methane production. Madhuni Madhushika Wijesooriya found that methanogens, the microorganisms responsible for methane formation, respond differently to these capture chemicals, with some being highly sensitive while others remain active at higher concentrations. She also studied how these chemicals interact with microbial cells and identified key properties that determine their compatibility with microbial activity. In addition, the research showed that microbial communities in mixed microbial cultures can change over time and that identifying specific microbial strains can support enhanced methane production. These findings contribute to a better understanding of microbial responses and support the use of microorganisms for reducing carbon emissions while producing renewable fuels from captured CO₂.

The PhD study was completed at the Department of Biological and Chemical Engineering, Faculty of Technical Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Monday, 01 June 2026 at 13:00
Place: Building 3130, room no. 303, Lecture Theatre Undervisning, Department of Biological and Chemical Engineering, Aarhus University, Gustav Wieds vej 10 D 8000 Aarhus C
Title of PhD thesis: Bio-Integrated CO₂-to Methane: Exploring the Methanogenic Responses to CO₂-Capture Agents 
Contact information: Madhuni Madhushika Wijesooriya, e-mail: mmw@bce.au.dk, tel.: +45 52729211
Members of the assessment committee:
Professor Amelia-Elena Rotaru, Department of Biology, University of Southern Denmark, Denmark
Professor Diana Machado de Sousa, Subdivision Microbiology, Wageningen University, Netherlands
Associate Professor Bekir Engin Eser, (chair), Department of Biological and Chemical Engineering, Aarhus University, Denmark 
Main supervisor: Associate Professor Michael Vedel Wegener Kofoed, Department of Biological and Chemical Engineering, Aarhus University, Denmark
Co-supervisor: Professor Lars Ditlev Mørck Ottosen, Department of Biological and Chemical Engineering, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English
The defence is public.
The PhD thesis is available for reading at the Graduate School of Technical Sciences/GSTS, Ny Munkegade 120, building 1521, 8000 Aarhus C.