Environmental Research Institute - Doctoral Theses

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Integrating air quality modelling, low-cost sensing and greenspace quantification for enhanced urban air quality and net-zero cities
(University College Cork, 2024) O'Regan, Anna Claire; Nyhan, Marguerite; Hellebust, Stig; O'Dowd, Colin; SFI Research Centre for Energy, Climate and Marine; University College Cork
Urbanisation is rapidly increasing worldwide. Currently, 55% of the global population live in urban areas and this is projected to increase to 70% by 2050. While urban areas are sites for innovation and economic growth, they are also key hotspots for poor air quality and climate-related impacts. Air pollution poses a significant risk to public health, with 96% of urban populations exposed to unhealthy levels of air pollution. As such, data on urban air quality is essential to identify pollution sources as well as spatial and temporal trends. This can support the formation of policies, ensuring compliance with regulatory limits while striving to meet the stringent World Health Organization (WHO) guidelines to protect public health. Air pollution and greenhouse gas (GHG) emissions often stem from common sources. Consequently, there is significant potential to develop policies that enhance air quality while also maximising reductions in GHG emissions. Rapid urban expansion is significantly impacting greenspace, with a notable decline observed due to increased demand for grey infrastructure. Greenspace offers many environmental benefits, including reducing air pollution and mitigating against the impacts of climate change, while also positively influencing residents’ health. As such, prioritising strategic greenspace developments is crucial. This research is driven by a need to improve our understanding of air pollution, greenspace and their associations, with an overarching aim of decarbonising cities. Firstly, a comprehensive review of global literature was conducted, identifying the current state-of-the-art in air pollution and GHG emissions modelling and monitoring efforts. Furthermore, innovative methods for quantifying urban greenspace were explored. Air pollution, specifically nitrogen dioxide (NO2), was modelled in high spatial and temporal resolution for Cork City, Ireland. The output of the dispersion model enables the identification of pollution sources while also capturing fluctuations in pollution levels over time and space. Moreover, a data fusion technique, regression kriging, was employed which integrated the urban dispersion model output with large-scale citizen science data. The citizen science data was measured using diffusion tubes at 642 locations across the study domain. The data-fusion model provided improved accuracy of air pollution levels and population exposure. Urban greenspace was quantified using 751,644 Google Street View (GSV) images, capturing a street-level view of greenspace at 125,274 locations across three major cities in Ireland. The associations between street-level greenspace, health and socioeconomics were explored. Higher levels of greenspace were associated with improved self-reported health and areas in the upper quartiles of greenspace had higher levels of income and lower levels of unemployment. Furthermore, with the advancements in air pollution sensing technologies such as ‘low-cost’ sensors, this research aimed to explore the relationship between greenspace and air pollution. This analysis demonstrated associations between higher levels of greenspace and lower levels of air pollution in urban areas. This research provides novel contributions across science and policy. It advances scientific knowledge and methodologies in air quality science and urban greenspace. Moreover, the research findings and high-resolution datasets can inform data-driven policies such as the National Clean Air Strategy (CAS) and Climate Action Plan, while also advancing UN Sustainable Development Goals including ‘Goal 11: Sustainable Cities and Communities’, ‘Goal 3: Good Health and Wellbeing’ and ‘Goal 13: Climate Action’. There is great potential to design effective strategies that strive to improve air quality and ensure optimal planning and provision of greenspace, thereby accelerating the transition to net-zero. Adopting an integrated approach in urban planning will ensure the development of cities that have good air quality, ample exposure to greenspace and net-zero emissions.
Advancing Irish energy system modelling to inform residential policy
(University College Cork, 2023) McGuire, Jason; Daly, Hannah E.; Rogan, Fionn; O'Gallachoir, Brian; Department of the Environment, Climate and Communications
Anthropogenic greenhouse gas emissions are rising, and a lack of action towards climate policy has sparked a renewed determination to act. Energy Systems Optimisation Models (ESOMs) help guide energy policymaking to meet climate goals. This thesis uses a newly developed ESOM, TIMES Ireland Model (TIM), to explore Ireland’s decarbonisation pathways. TIM incorporates empirical internal temperature variations in buildings. Building Energy Rating (BER) assessments in Ireland, based on Energy Performance Certificates (EPC), measure a building’s expected energy consumption. However, it has been observed that standard BER assessments tend to overestimate residential energy consumption in Ireland by as much as 23%. When empirical internal temperatures are used in place of BER temperature assumptions, 6% fewer thermal retrofits are required to achieve the cost-optimal decarbonisation pathway, but energy savings are 114% less in this case. The new methodology better reflects energy consumption without overestimating the effect of thermal retrofits and provides more accurate climate policy insights. The Danish Energy Agency supported this thesis by exploring the feasibility of district heating (DH) in Ireland. Ireland is a country with low DH deployment, but it has significant surplus heat. Using scenarios that considered different connection rates and maximum annual growth, this thesis consistently showed that DH saturates the heat market before 2050 in all scenarios. If DH is excluded, the average sectoral marginal CO2 emission price over the model’s time horizon is €729/tCO2. However, when DH is permitted, this cost reduces by 13% to 25%, depending on the connection rate and maximum growth constraint. A policy-focused aspect of this thesis explored Ireland’s current fabric-first policy approach to understand if it is cost-effective. Alternative decarbonisation pathways allow for variations in heat pump subsidy thresholds connected to a dwelling’s Heat Loss Indicator (HLI). The thesis also accounted for sub-optimal heat pumps, which do not achieve peak performance due to high HLIs. The findings suggest that the current fabric-first approach is stringent, requiring a BER rating of B2 or equivalent energy consumption, which is not cost-effective. Significant savings can be made, especially post-2030. For example, post-2030, the fabric-first average sectoral marginal CO2 emission price is €675/tCO2. Simply by allowing sub-optimal heat pump installation, this reduces to €312/tCO2. Adjusting the HLI threshold to 2.3 W/K/m² could further reduce this cost to €273/tCO2. This research offers a detailed exploration of the Irish residential sector, emphasizing the complex interactions among different energy sectors and advocating for a more coherent energy planning approach. For policymakers, it is essential to better understand residential energy consumption, embrace district heating through spatial energy system planning, and reevaluate the fabric-first approach. By doing so, Ireland could effectively achieve its climate goals more cost-effectively.
Decarbonisation of whiskey distilleries in a circular economy: investigating biorefinery systems for valorisation of distillery by-products
(University College Cork, 2024) Hackula, Anga Awonke; Wall, David; O'Shea, Richard; Murphy, Jerry; Irish Research Council
Decarbonisation of industrial processes is necessary to mitigate the detrimental impacts of anthropogenic climate change. Innovative technological solutions are sought that will allow for both a reduced carbon footprint and increased security of supply. The whiskey production industry produces by-products that are currently used linearly for animal feed. This thesis examines the use of by-products generated from whiskey production to enact a circular economy philosophy, which may be of further benefit to a distillery. This was achieved by examining various technologies, namely anaerobic digestion (AD), dark fermentation, and pyrolysis, in a cascading biorefinery concept. Central to the evaluation of the whiskey by-product valorisation through anaerobic digestion was the development of a novel two-phase anaerobic digestion system, termed a leach bed reactor – expanded granular sludge bed (LBR-EGSB). Several design modifications, including the implementation of a cost-effective siphon-actuated leachate attenuation system, advanced the configuration beyond comparable designs. The LBR-EGSB could successfully convert the by-products into volatile fatty acids (VFAs) and methane-rich biogas (75 %vol). The LBR-EGSB was compared to traditional anaerobic digesters for energy production capabilities, showing similar biomethane potential, which could satisfy approximately 44 % of the thermal energy demand of a large distillery operating in Ireland. Furthermore, the research investigated the potential of a biorefinery utilising dark fermentation, whereby the whiskey by-products were converted into biogenic carbon dioxide for use in beer carbonation, biohydrogen for use as transport or heating fuel, and VFAs for use as bioplastic beer packaging. A 50 million-litre whiskey distillery could satisfy approximately half of the carbon dioxide requirement of the Irish brewing industry. Biohydrogen was found to be best suited as a transport fuel. The VFAs could be processed into bioplastics which could completely satisfy beer packaging demand in Ireland. Continuous VFA production and demand-driven biogas production to generate electricity during peak demand hours were also evaluated. The systems analysed were a two-phase continuously stirred tank reactor (CSTR) and the designed LBR-EGSB. Both systems exhibited continuous VFA production (up to 10.4 g. L-1Leachate) and rapid biogas production, achieving peak biogas flow rates within 30 minutes. A theoretical evaluation of processing butyric acid into biobutanol, to be blended with diesel, could produce a more sustainable transport fuel than diesel, reducing distillery-associated transport emissions by 16 %. Additionally, the novel use of whiskey barrel-derived biochar was compared to commercial carbonaceous materials, revealing its efficacy in enhancing biohydrogen and biomethane production by 15% and reducing methane production lag time, thereby advancing the understanding of pyrolysis parameters' impact on anaerobic digestion. Overall, this thesis demonstrates that integrating AD systems, biochar application, and innovative biorefinery concepts can significantly enhance the sustainability of whiskey distilleries, proposing a pathway for modern circular economy strategies and decarbonisation of the whiskey distillery industry.
Exploring the microbial ecology and energetics of wild and domesticated Atlantic salmon (Salmo salar)
(University College Cork, 2023) Schaal, Patrick Daniel; McGinnity, Philip; Reed, Thomas; Llewellyn, Martin; Biotechnology and Biological Sciences Research Council; Science Foundation Ireland; Higher Education Authority
Since the inception of Atlantic salmon (Salmo salar) aquaculture in the 1970s, millions of domesticated fish have escaped from aquaculture facilities into the wild. This phenomenon raises concerns about the ecological and genetic consequences of farmed fish interbreeding with their wild counterparts. The fitness of hybrid offspring from such interactions has long been recognised as diminished compared to pure wild salmon populations, thereby posing a substantial threat to the overall health and robustness of Atlantic salmon populations. This study takes a comprehensive approach to investigate the impact of domestication on two vital aspects of Atlantic salmon biology: gut microbial communities and metabolism. Both traits have been identified as critical determinants of fish health and well-being. To disentangle the genetic effects from confounding environmental factors, this study employed common garden experiments. These experiments involved rearing fish with diverse genetic backgrounds, including wild, domesticated and reciprocal hybrids, together from the eyed-egg stage through both freshwater and marine phases. This design allowed us to simulate farmed escape and hybridisation events that naturally occur in the wild. The first data chapter examines the drivers and sources that shape gut microbial assembly over time in juvenile Atlantic salmon in a natural river system. The study shows that the major contributors to the salmon intestine's microbial taxa come from macroinvertebrates, a potential food source, rather than the water column. Moreover, results suggest a possible role of host genetics in driving inter-individual differences in gut microbial community composition, leading to distinct microbiota assemblages between farmed, wild and hybrid fish. Neutral modelling further revealed that the majority of gut taxa are transient, underscoring the dynamic nature of these microbial communities and emphasizing the need to distinguish between transient and resident taxa within the gut environment. The second data chapter examines the seasonal dynamics of gut microbial communities and energetics in juvenile Atlantic salmon, considering potential variations among farmed, wild and hybrid fish. The study unveils genetic factors as significant influencers of metabolic flexibility in Atlantic salmon. Wild fish exhibit lower metabolic rates in winter and higher rates in summer compared to farmed salmon, indicating their adaptability to seasonal environmental changes. This metabolic flexibility potentially enhances their chances of survival in variable wild environments compared to their farmed counterparts, which might exhibit less adaptability due to artificial selection for commercially favoured traits. Furthermore, our research unveils shifts in gut microbial communities during the winter months, particularly among the offspring of wild fish, possibly attributable to reduced feeding activity. This reduced activity, in turn, might be associated with their generally lower metabolic demands in winter. The third data chapter assesses whether survivability, gut microbial structure and metabolic rate of Atlantic salmon reared in marine sea pens are affected by amoebic gill disease (AGD), a parasitic infection that poses a significant challenge to Atlantic salmon reared in aquaculture facilities, and if those effects vary between fish from farmed, wild and hybrid origins. Wild fish exhibited substantially higher mortality rates compared to their farmed counterparts, while hybrids fell in between. All fish, regardless of genetic origin, showed significantly lower metabolic rates with increased AGD infection rates. In addition, gut microbial diversity significantly declined in AGD-infected fish. In summary, our study significantly contributes to our understanding of the complex interactions between host genetics, environmental factors and gut microbiota in Atlantic salmon. It offers indications that the domestication process in Atlantic salmon has influenced both host-associated microbiota and metabolism. As aquaculture continues to expand, these findings underscore the need for comprehensive conservation strategies to safeguard the ecological integrity of wild Atlantic salmon populations in the face of evolving aquaculture practices and the potential consequences of farmed fish escape events.
Enhanced modelling of transport decarbonisation and policy pathways for Ireland
(University College Cork, 2023) O'Riordan, Vera; Rogan, Fionn; Daly, Hannah E.; O'Gallachoir, Brian; Climate and Energy Modelling Services
The release of increasing human-induced greenhouse gas emissions and the corresponding global temperature rise has prompted a growing political consensus on a decarbonised future to prevent any sustained economic or environmental harm. Many countries are using energy system modelling tools to develop strategies and policy measures to deliver timely and effective reductions of harmful greenhouse gas emissions across all energy-related sectors. Ireland, with ambitious legally binding carbon budgets, and decarbonisation targets for transport, is a country in the process of assessing and addressing key transport decarbonisation challenges faced by high-emitting countries. This thesis - with its scientific contributions on transport emissions, methodological advancements for transport and multi-sector energy systems simulation modelling, and policy recommendations on how effective measures have been in the past or could be in the future - serves as a small, but novel, piece of this process. The thesis updates the Irish Car Stock Model to investigate the importance of taxation policy using a novel bottom-up stock simulation approach. The simulation model evaluates the 2008 car tax policy in Ireland and finds that while the policy was effective at reducing CO2 emissions, it had a high cost of carbon abatement, between €1,500 – 2,200 per tCO2. The thesis develops the Irish Passenger Transport Emissions and Mobility (IPTEM) model, which for the first time, calculates the overall passenger transport demand in Ireland by trip purpose, trip distance, and mode type. The methodological advancement is in the combination of passenger transport demand from all modes of transport and information from the National Travel Survey, national transport providers, and the Irish Car Stock Model. The study finds that 82% of passenger transport demand is met by cars in Ireland, and the main reason for travel is for work (30%), shopping (19%), and companion journeys (16%). The study also finds that 40% of emissions come from journeys less than 8 kilometres. In Chapter 4, this thesis develops a new model, the LEAP Ireland ASI (Avoid-Shift-Improve) model which projects emissions and demand for passenger and freight transport up to 2030. It is novel in its application of the Avoid-Shift-Improve framework for scenarios focused on reducing the need to travel in the first instance (“Avoid”), then on modal shifting towards increased public transport use and active travel (“Shift”), and then on scenarios focused on improving the fuels used to ones with a lower carbon intensity (“Improve). These scenarios are modelling in combination with one another and the interaction between the policies is also determined. In Chapter 5, the thesis develops a new methodology for simulation modelling to project carbon dioxide emissions, how different scenarios could reduce carbon dioxide emissions, and how these fit in with sectoral emissions ceilings within carbon budgets. The thesis tracks past sectoral emissions and simulates the mitigation potential of a suite of scenarios for transport, residential, electricity, services, and industry sectors. The LEAP Ireland model developed in Chapter 5 can simulate the impact of additional policies, track policy performance, and simulate mitigation potential. The data sources, methodology, and carbon budget analysis are outlined in this novel simulation modelling framework designed to support countries with their carbon budgeting commitments. This thesis also examines the interaction effect between these policy scenarios and discusses their combinations' synergistic and antagonistic effects. The contribution of this thesis is the improvements made to the modelling methods and more robust evidence base for developing sound decarbonisation transport policy measures by shifting the focus beyond car efficiency and electrification.

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