Disputas: Vida Ahmadi-Olsen

Vida Ahmadi-Olsen skal forsvare avhandlingen sin for graden philosophiae doctor (ph.d.) ved Universitetet i Sørøst-Norge.

Hun har fulgt doktorgradsprogrammet i teknologi ved Fakultet for teknologi, naturvitskap og maritime fag 

Alle interesserte ønskes velkommen til prøveforelesning og disputas, enten fysisk eller digitalt.

• Les avhandlingen her.

Sammendrag

Biogas is a renewable fuel produced by microbes breaking down organic waste through anaerobic digestion (AD), supporting the green transition. However, biogas contains a large share of carbon dioxide (CO₂), which lowers its heating value and limits its application. Converting this CO₂ into methane (CH₄) adds value to the fuel product and contributes to reducing greenhouse gas emissions. Electrochemical systems enable the conversion by harnessing electrical energy to drive the reaction, but traditional approaches demand high amounts of energy and expensive electrode materials. Bioelectrochemical systems (BES) offer a promising alternative, utilizing electrode-associated microorganisms as biocatalysts to reduce energy input and improve process sustainability. These microbial catalysts lower the energy demand and contribute to a more sustainable operation. However, large-scale applications is still under development as current systems face challenges such as limited electrode durability, efficiency losses, and inconsistent performance when scaling from the laboratory to industrial scales.

This PhD project addressed these challenges by developing efficient electrode materials and reactor design, and by combining experiments with mathematical modeling. Surface treatments and coatings on stainless-steel electrodes were shown to increase CH₄ production, lower electrical energy input, and reduce electrode corrosion, making the systems more reliable. Microbial communities enriched on these electrodes worked together with the materials to achieve high CH₄ yields. At the same time, models were built to understand how voltage, microbial growth, and reactor design influence performance, and to provide predictive tools for scaling up.

The results showed that the new reactor design and electrode improvements could produce biogas with up to 96 % CH₄ content, the lowest possible energy input and with a very low mass loss rate of electrodes, proving their durability. Mathematical modeling confirmed these findings and helped predict how larger systems can operate efficiently. In summary, this PhD research work demonstrates a practical approach by enabling efficient biogas upgrading alongside wastewater treatment.