A long journey from bioanode to biocathode
Doktorsavhandling, 2018

Better utilization of renewable sources of energy and recovery of resources from waste streams are important challenges for researchers. Bioelectrochemical systems (BESs) are new technologies which e.g. could be used to produce green energy from waste sources or store renewable electricity as chemical fuels. They rely on microorganisms which can catalyse oxidation/reduction reactions on anodes/cathodes. BESs have a wide range of potential applications such as sensing, bioremediation, recovery of nutrients and metals, valorisation of wastewater organics, and production of energy carriers and other chemicals. However, further research is needed before these applications can be realized.

The goal of this thesis was to understand the effect of three different dynamic conditions and disturbances that bioanodes and biocathodes may encounter namely storage, starvation, and potential change. Storage and starvation are disturbances that can affect biological electrodes in all kinds of systems, and it is important to understand their consequences for performance. Changing electrode potential has been shown as a promising method for start-up of biocathodes from enriched bioanodes, but little is known about the long-term performance and changes in microbial community composition as the biocathode develops.

First, the possibility for storage of acetate-oxidizing bioanodes using refrigeration, glycerol freezing, and acetone dehydration was investigated. It was shown that storage of acetate-oxidizing bioanodes was possible. Bioanodes stored using refrigeration were the only electrodes that showed biological activity right after five weeks of storage. Then, starvation of acetate-and glucose-fed bioanodes was investigated. It was shown that the acetate- and glucose-fed bioanodes can survive 10 days starvation. However, the overall performance of the glucose-fed bioanodes deteriorated more after each starvation phase compared to the acetate-fed bioanodes. The conversion of acetate- and glucose-fed bioanodes to biocathodes was also compared. Immediately after the potential change, the glucose-fed bioanodes showed better cathodic activity but over time the performance converged. Then, we compared the conversion of bioanodes to biocathodes with direct start-up of biocathodes from a wastewater inoculum. Bare electrodes started-up faster compared to pre-enriched bioanodes. In the end, both types of enrichment procedures led to very similar biocathode communities, which were completely different from the bioanode communities. Indeed, for the microbial communities, it was a long journey from bioanode to biocathodes. Hydrogen appeared to be an important intermediate in the biocathode biofilms, therefore, start-up of biocathodes with pre-enriched hydrogenotrophic cultures was investigated. Hydrogenotrophic microorganisms could facilitate start-up of the biocathodes. All the microbial electrolysis cells inoculated by the enrichment cultures started to generate noticeable current directly after inoculation.

In summary, the bioelectrodes in our experiments were robust and could handle storage and starvation periods although the results depended on the experimental conditions, the feed, and the microbial communities. Conversion of bioanodes into biocathodes was less successful and resulted in a complete transition of the microbial community on the electrode. Start-up of biocathodes with hydrogen-oxidizing enrichment cultures was a more successful strategy.

Biocathode

Bioelectrochemical system

Storage

Starvation

Microbial electrolysis cell

Bioanode

Microbial fuel cell

Mixed microbial communities

Hydrogenotrophic microorganisms

SB-H6, Sven Hultins gara 6, Göteborg
Opponent: Dr. Deepak Pant, Flemish Institute for Technological Science (VITO), Belgium

Författare

Soroush Saheb Alam

Chalmers, Arkitektur och samhällsbyggnadsteknik, Vatten Miljö Teknik

Effect of start-up strategies and electrode materials on carbon dioxide reduction on biocathodes

Applied and Environmental Microbiology,; Vol. 84(2018)

Artikel i vetenskaplig tidskrift

Effects of storage on mixed-culture biological electrodes

Scientific Reports,; Vol. 5(2015)p. no. 18433-

Artikel i vetenskaplig tidskrift

SAHEB-ALAM, S., PERSSON, F., WILEN, B. M., HERMANSSON, M. & MODIN, O. Biodiversity, community composition and response to dynamic conditions of microbial electrodes enriched on acetate and glucose.

SAHEB-ALAM, S., PERSSON, F., WILEN, B. M., HERMANSSON, M. & MODIN, O. A variety of hydrogenotrophic enrichment cultures catalyse cathodic reactions.

Limited resources of fossil fuels and their negative impact on the Earth has motivated researchers, in both academia and industry, to search for renewable green energies, which contribute less to environmental stresses such as climate change and global warming. Another global problem is the management of municipal- and wastewater and other waste streams. Microbial electrochemical systems are modern sustainable green technologies that have been introduced in the last few decades and could in various forms contribute to energy generation and storage, resource recovery from waste streams, and degradation of pollutants in wastewater and the environment.  In microbial electrochemical systems, living microorganisms function as catalysts for reactions on the anode and/or the cathode. There is a variety of potential applications ranging from wastewater treatment and biogas generation to production of chemicals. Systems with bioanodes could be used to convert organic compounds to electrical current and systems with biocathodes could be used to reduce CO2 to methane, acetate, or other high-value chemicals. During the operation of such systems, biological electrodes may encounter disturbances that can affect their performance and microbial community composition. The work in this thesis assesses the effects of three disturbances, namely storage, starvation and potential changes on the biological electrodes enriched in microbial fuel cells and microbial electrolysis cells.

Drivkrafter

Hållbar utveckling

Ämneskategorier

Vattenteknik

Annan naturresursteknik

Annan kemiteknik

Energisystem

Vattenbehandling

Biokatalys och enzymteknik

Styrkeområden

Energi

Livsvetenskaper och teknik

ISBN

978-91-7597-756-0

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4437

Utgivare

Chalmers tekniska högskola

SB-H6, Sven Hultins gara 6, Göteborg

Opponent: Dr. Deepak Pant, Flemish Institute for Technological Science (VITO), Belgium