Biological transformation of geothermal gases to biomass: A case study

Abstract

Geothermal electricity generation releases waste gases, including the greenhouse gases methane and carbon dioxide. These gases are currently vented to the atmosphere or re-injected, however there is potential to turn this waste stream into commercial products. This case study profiles the first project to couple the production of a protein with geothermal gases and extremophilic microorganisms sourced from geothermal environments.
Laboratory scale-research experimentally demonstrated proof of concept, showing that a co-culture of endemic geothermal microorganisms (a bacterium and a microalga) can consume the industrial gases, carbon dioxide (CO2) and methane (CH4) as a food source for growth. This generates a biomass that is rich in protein (ca. 60%) and was shown to be non-toxic, nutritious, and digestible (in mice). The biomass produced also contains several potentially valuable components, which could be extracted to enhance commercial viability.
To advance towards commercialisation, we are scaling up from laboratory (80 L) to pilot scale (ca. 900 L) to optimise operating conditions and test with actual geothermal gases on a geothermal steam-field site. The scale-up will generate sufficient volumes to trial the biomass on larger, commercially-farmed animals and/or fish, as well as allow for fractionation experiments to explore the viability of premium products. Concurrent with the technical development, we are evaluating target markets and pathways to these markets, including regulatory requirements and analysis of the techno-economics. This paper and presentation shares the project history, goals and learnings to date.