Abstract
Subsurface energy extraction technologies could play an important role in meeting UK energy demands whilst reducing emissions and improving energy security. These technologies interact with the terrestrial subsurface, impacting the abundant and diverse resident microorganisms and the ecosystem services they provide. Furthermore, microbial growth can damage infrastructure, reduce operational efficiency, and increase the risk of industrial leaks. The aim of this thesis is to investigate changes to microbial community structure and function induced by geothermal and shale gas energy extraction in the UK.The microbiological composition of soil and rock core samples from a minewater geothermal energy observatory (UKGEOS) and flowback fluids from the only UK hydraulic fracturing site (PNR) were investigated using cultivation methods (agar plates, enrichments, microcosms) and DNA sequencing. Cultivation and DNA extraction from rock cores were unsuccessful, highlighting the technical difficulties of analysing low biomass rocks and the extreme conditions faced by subsurface microorganisms. Media enrichments of flowback fluids facilitated the identification of persistent microorganisms to species level, including taxa that exhibit biocide resistance and could cause biocorrosion. These microbial communities preferentially used guar gum over polyacrylamide for growth, suggesting polyacrylamide may be more suitable for use in some operations. Microbial growth of PNR microorganisms in the presence of glutaraldehyde confirmed biocide resistance, indicating that glutaraldehyde may not sufficiently prevent microbially induced infrastructure problems. Glutaraldehyde biodegradation also occurred with UKGEOS soil microorganisms when incubated in isolation or with guar gum, polyacrylamide, and salt. While salinity did not significantly impact biodegradation, abiotic interactions between the chemicals demonstrated that compounds considered biodegradable may behave differently in mixtures, with implications for environmental bioremediation. This research provides important information that can improve the assessment and mitigation of the environmental impacts of subsurface energy extraction and makes a valuable contribution to our limited understanding of the UK’s terrestrial subsurface biosphere.
| Date of Award | 10 Dec 2024 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Heather L Buss (Supervisor) & Tom Williams (Supervisor) |