Description
ABSTRACT
Very little is known on the ecosystem impacts of emissions from geothermal power plants. The emissions, comprising mainly of non condensable gases (NCGs) i.e. carbon dioxide, hydrogen sulphide, methane and trace elements such as arsenic, boron, antimony and mercury, have the potential to deposit and accumulate in ecosystems. At elevated levels, some NCGs can cause ecosystem stress, especially H2S and the trace elements. The aim of this thesis is to assess the effects of these elements on terrestrial ecosystems around two geothermal areas in contrasting biomes i.e. Kenya and Iceland.
Dominant plant species around each geothermal study area, Tarchonanthus camphoratus shrub in Kenya and Racomitriumlanuginosum moss in Iceland, were used as bio-indicators and concentrations of sulphur, arsenic, boron, antimony and mercury were mapped in their tissues and soils at increasing distances from the power plants along the prevailing wind direction in field surveys. Patterns of plant growth and health along the same distances and wind direction gradients were also studied to assess any potential effects related to the power plants. Controlled experiments were thereafter carried out on the same plant species to assess in detail the effects of the most abundant phytotoxic NCG, i.e. H2S gas, on plant growth and health. Results of the field surveys and experiments indicated that the main geothermally emitted component, H2S gas, deposits and accumulates in plants and soils. The measured trace element concentrations in plants and soils (from the field surveys): arsenic, boron, antimony and mercury, did not show strong patterns attributable to the geothermal power plant emissions. Further, results of the surveys in relation to geothermal power plant emissions showed weak indications of effects on Tarchonanthuscamphoratus shrub growth and health around the Olkaria geothermal power plants in Kenya. Additionally, the experiments showed that, 30 μg/L aqueous H2S (10.96 ppm in air) may be a tolerable limit for plants around geothermal power plants in Kenya. These findings serve as important baseline data toward environmental monitoring and management around both geothermal power plant area in Kenya; this information is also of utmost importance in advising the public and decision makers in Kenya on the ecosystem (terrestrial) impacts of geothermal power plant emissions.
TABLE OF CONTENTS
Title Page
Approval Page
Dedication
Acknowledgement
Abstract
Table of Content
CHAPTER ONE
1.0 Introduction
1.1 Background and Significance of Geothermal Energy in Kenya
1.2 Objectives and Scope of the Study
1.3 Scope of the Study
1.4 Organization of the Thesis
CHAPTER TWO
2.0 Literature review
2.1 Overview of Geothermal Energy
2.2 Geothermal Energy in Kenya
2.3 Environmental Impacts of Geothermal Fluid Emissions
2.4 Regulatory Framework and Environmental Management Practices
2.5 Chapter Summary
CHAPTER THREE
3.0 Methodology
3.1 Introduction
3.2 Research Design and Philosophy
3.3 Research Approach and Study Area
3.4 Data Collection Methods
3.5 Data Analysis Techniques
3.6 Regulatory Review and Stakeholder Engagement
3.7 Environmental Management Recommendations
3.8 Ethical Considerations
CHAPTER FOUR
RESULT ANALYSIS
4.0 DATA ANALYSIS, RESULT AND DISCUSSION
4.1 Introduction
4.2 Field surveys
4.3 Experiments
4.4 Data analyses
4.5 Results and Discussions
CHAPTER FIVE
5.0 Conclusions and Recommendation
5.1 Conclusion
5.2 Recommendation
5.3 References
CHAPTER ONE
1.0 INTRODUCTION
Geothermal energy has surfaced as a promising renewable energy resource, due to its capacity to deliver clean, sustainable, and dependable electricity (Anderson and Rezaie, 2019). Kenya has been a leader in Africa when it comes to developing geothermal energy. The country uses its abundant geothermal resources to power its expanding energy needs (Avci et al., 2020). Nevertheless, the investigation and utilization of geothermal resources might result in notable environmental consequences, specifically regarding the release of geothermal fluids (Jolie et al., 2021). Geothermal fluids, obtained from subterranean reservoirs during the generation of geothermal energy, comprise a diverse range of chemical constituents, such as gases, dissolved solids, and suspended particles (Meller et al., 2017). These emissions have the potential to harm natural systems, water resources, soil health, and air quality if they are not controlled (Brouwer, 2018; Manisalidis et al., 2020; Siddiqua et al., 2022). The release of greenhouse gases, the degradation of water quality from geothermal effluent discharge, and the disturbance of ecosystems through changes in land use are just a few ways in which the exploration and exploitation of geothermal resources could impact the surrounding environment (Shortall et al., 2015; Dhar et al., 2020; Soltani et al., 2021). The sustainable development of geothermal energy in Kenya depends on effective management and mitigation techniques to minimize these environmental repercussions (Gichuhi et al., 2020; Soltani et al., 2021).
This study seeks to examine the ecological consequences of geothermal fluid emissions in Kenya, acknowledging the significance of sustainable geothermal energy development. The study aims to enhance the existing knowledge on geothermal energy and its environmental concerns by analyzing the characteristics and magnitude of these emissions, as well as their potential impact on the environment.
1.1 Background and Significance of Geothermal Energy in Kenya
Among African countries, Kenya has been a pioneer in developing methods to use geothermal energy. In 1981, Kenya embarked on its path to become a geothermal energy sector leader with the commissioning of Olkaria I, the country’s first geothermal power plant (Mangi, 2018). Subsequently, the advancement of geothermal energy has been crucial in expanding Kenya’s energy sources, diminishing its dependence on fossil fuels, and fulfilling the increasing need for electricity due to industrialization and population expansion (Carvallo, et al., 2017).
Kenya possesses a remarkable geothermal potential, with an estimated capacity of over 10,000 megawatts (MW) of resources situated throughout the East African Rift System (Benti et al., 2023). In 2022, the country’s geothermal power capacity reached 863 MW, establishing it as the leading generator of geothermal energy in Africa and the eighth-largest internationally (Venomhata et al., 2023).
The Kenyan government has acknowledged the significant value of geothermal energy in attaining its national energy strategy goals of guaranteeing accessible, dependable, and enduring energy provision (Lemi, 2023). Geothermal energy offers a sustainable and environmentally friendly means of generating continuous power, while also promoting economic growth, employment opportunities, and the mitigation of greenhouse gas emissions (Soltaniet al., 2021).
Nevertheless, the investigation and utilization of geothermal resources come with environmental repercussions. Extracting geothermal fluids from underground reservoirs can lead to the emission of diverse chemical compounds, such as gases, dissolved solids, and suspended particles. These emissions have the potential to affect the quality of air, water resources, soil health, and ecological systems in the surrounding areas (Zucca et al., 2003; Wassie, 2020).
Given the ongoing growth of the geothermal energy industry in Kenya, it is imperative to comprehensively comprehend and mitigate the environmental consequences linked to the release of geothermal fluids.
1.2 Objectives and Scope of the Study
The primary objective of this study is to evaluate the environmental effects linked to the release of geothermal fluids from geothermal power facilities in Kenya. More precisely, the study seeks to:
- Analyze the content and characteristics of geothermal fluid emissions, including gases, dissolved solids, and suspended particles, originating from specific geothermal power facilities in Kenya.
- Assess the possible environmental consequences of these emissions on the quality of air, availability of water resources, condition of soil, and functioning of ecological systems in the nearby regions.
- Evaluate and examine the current regulatory framework, recommendations, and optimal methods for reducing the environmental consequences of geothermal fluid emissions in Kenya.
- Offer guidance to policymakers, geothermal energy developers, and other relevant parties on strategies to diminish the ecological impact of geothermal energy generation in Kenya.
1.3 Scope of the Study
This study focuses exclusively on evaluating the environmental consequences that arise from the release of geothermal fluids during the operation of geothermal power facilities. It excludes other possible environmental effects linked to the exploration, drilling, construction, or decommissioning stages of geothermal energy development. The study will concentrate on a specific group of geothermal power facilities in Kenya, which will be chosen to represent various geographical areas and operational features. This approach aims to obtain a thorough comprehension of the matter under investigation. The study will employ a blend of field data collecting, laboratory analysis, and literature evaluation to acquire and scrutinize pertinent information.
1.4 Organization of the Thesis
The thesis is structured into six primary chapters, in addition to references and appendices.
Chapter 1: Introduction
This chapter presents a comprehensive introduction to the research subject, encompassing the historical context and importance of geothermal energy in Kenya, the goals and extent of the study, and the structure of the thesis.
Chapter 2: Literature Review
This chapter provides a thorough examination of pertinent literature, encompassing a summary of geothermal energy, the exploration and utilization of geothermal energy in Kenya, the ecological consequences of geothermal energy emissions, and instances and optimal methods for minimizing environmental repercussions.
Chapter 3: Methodology
This chapter outlines the specific methodological approach employed for the study, encompassing information on the study region, techniques for data collecting and analysis, as well as the criteria and indicators utilized to evaluate the environmental effects of geothermal fluid emissions.
Chapter 4: Results and Discussion
This chapter covers the study’s findings, commencing with a comprehensive overview of the progress made in geothermal energy production in Kenya. Subsequently, it offers a description of geothermal fluid discharges, followed by an examination and assessment of the ecological consequences of these discharges on the atmosphere, aquatic bodies, land, and biological systems.
Chapter 5: Mitigation Measures and Best Practices
This chapter examines several tactics and measures aimed at mitigating the environmental effects caused by the release of geothermal fluids. The text examines the legislation and norms pertaining to the development of geothermal energy in Kenya. It also presents case studies and insights gained from other locations that have successfully implemented geothermal energy production.
Chapter 6: Conclusion and Recommendations
This chapter provides a concise overview of the main discoveries made throughout the study and offers suggestions for policymakers, geothermal energy developers, and other interested parties to promote the sustainable and responsible growth of geothermal energy in Kenya. Additionally, it addresses the constraints of the study and proposes avenues for future investigation.
5.1 Conclusions and Recommendation
In the field surveys presented work, there is evidence that sulphur(in the form of hydrogen sulphide gas)emitted from the geothermal power plants in Kenya(Olkaria)deposits and accumulates in terrestrial ecosystems in the vicinity of the power plants. However, the trace element concentrations: arsenic, boron,antimony and mercury, do not show such consistent and similar patterns;according to data from this study, their levels in terrestrial ecosystems in the Kenya study area cannot be attributed to the geothermal power plants.Further,because trace elements are not monitored in the emissions and their concentrations are not known, it is difficult to conclude that the measured trace element concentrations in the plants and soils may to some extent have been influenced by the power plants. This conclusion is slightly distinct from the Meditteranean studies(Baldi, 1988; Bargagliet al., 1997; Bussotti et al., 1997; Bacci et al.,2000) that report high sulphur and trace element concentrations in plants and soils near geothermal power plants with patterns indicating potentialenrichmentfromthepowerplantemissions.TheMeditteraneangeothermal systems are different. In terms of aquifer fluid phases, the Mediterranean geothermal systems are mainly dry steam dominated(Bertinietal.,2006),different from the liquid-vapour dominated geothermal systems in Kenya (Koech, 2014). The trace elements in the Kenya study context are not nearly as volatile as the H2S gas and may not have been in very high concentrations in the NCGs of the geothermal power plants in Kenya.
The plants (bio-indicators) in the field survey showed some indications of geothermal power plant effects on plant growth that corresponded to the findings of geothermally enriched sulphur in their tissues and soils. This may suggest that the effects on plants are somehow related to the excess sulphur levels in the plant tissues and soils and may be affecting plant growth. However,the influence of other environmental factors is to be considered, as for example the soil conditions were in most part significant in explaining the variations of the different element concentrations in the plants and soils.
Due to the indications of effects on plant growth noted,further field surveys are recommended for both areas for better assessments of sulphur effects on plants and especially in relation to bio-accumulation in the ecosystem.
Further long term studies are recommended to properly evaluate sulphur accumulation in plants in relation to the geothermal power plants and associated plant growth/health effects, because of the moderate to slow growing nature of the plants: T. camphoratus is reported to grow between 600–800mm/year(Orwaetal.,2009)and R.lanugiosum up to 5mm/year (Tallis, 1964; Jónsdóttir et al., 1995). For the Kenya survey, it may even be more interesting to combine the shrub assessments with other additional and sensitive bio-indicators such as lichens and mosses orsoil-microbes(Baldi,1988;Loppietal.,1998;Bargaglietal.,2002;Zouboulisetal.,2004;Storelli,2013).Further responses of T.camphoratus related to growth and physiology can also be included in the studies, including recruitment of new flowers, leaf area, leaf biomass and photosynthesis.
In an improved study design, the addition of more study transects around the power plants and a large number of replicates could provide clear information on element distribution and effects around the power plant areas to complement our findings. New study transects perpendicular to the main transects of the two field surveys are interesting to explore to get an overall picture of element distribution and plant responses over the entire geothermal area.
Furthermore,short term exposure to moderate levels of H2S deposition(30 µg/L (ppb) approximately 10.96 ppm air concentrations) does notresult in harm to the two plants. This H2S level seemed to benefit plant growth in the shrub T. camphoratus, and did not reduce R. lanuginosummoss growth. However, high exposure concentrations of H2S depositions(300µg/L(ppb)–about 109.57 ppm air concentrations) reduced R.lanuginosum growth but did not affect T.camphoratus growth. The observed effects on plant health with in the short duration of the experiment are indicative that if the experiment is conducted for a long duration, stronger and clear responses would be evident. A follow-up experiment over a longer period is thus recommended. It is important because these plants,within their natural set-up,are usually exposed(although not directly) to emissions (dry and wet deposition) over a long period of time, that is as long as the power plant operates. A detailed understanding of the effects on plant health is important for planning of mitigation measures.
5.2 RECOMMENDATION
In future experiments, the growth conditions for the R. lanuginosum canbe improved by carrying out the experiments in the field and away from any atmospheric pollution activities rather than in a growth chamber. This is due to the atmospheric sensitivity of mosses,for instance in this experimental study,growth chambers were slightly hotter than normal and may have affected R.lanuginosum growth as it is susceptible to drying on exposure to high heat.
Since more ecosystem effects were noted in Iceland than in Kenya, it is recommended that the geothermal power plant developer at Hengill inIceland fosters emission curbing mechanisms to prevent future effects of sulphur depositions interrestrial ecosystems. Reykjavík Energy,the power developer at the Hellisheidi geothermal project,is already undertaking trials of a H2S emission abatement strategy by testing the feasibility of H2Sre-injection back into the earth(Gun narssonetal.,2013).This project should be fully supported at all levels to ensure sustainable geothermal power development. In addition, monitoring of trace elements from the power plant emissions is highly recommended atthe Olkaria and Hengill geothermal power plants, as at present knowledge is lacking on which trace elements are emitted,their concentrations,amounts and fate from geothermal power plants emissions. Monitoring of the trace element levels in emissions is thus advised for mitigation of any likely associated effects.
Overall, these findings serve as a necessary yardstick in advising future geothermal projects. Especially because the target species are also common in some of the other ear marked geothermal fields for development in Kenya. For example,the species T.camphoratus is also a bundant in Suswa and Menengai geothermal area in Kenya. Furthermore, the general findings will advise policy makers, conservationists and the public on the effects of these emissions on ecosystems and the urgent need for development of air quality environmental guidelines related to geothermal power plants. This new knowledge will also increase public awareness on the effects of geothermal power plants on the environment and reduce uncertainties or ambiguities on such projects, an important aspect in increasing social confidence and possibly public acceptance and support of geothermal projects.
