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Integrating mineral wastes in the anaerobic digestion of OFMSW for improved recovery of renewable energy
Get PDFPhD ThesisThis thesis investigated the effects of mineral wastes (MW) on laboratory-scale anaerobic reactors treating organic wastes. Different MW resources were used, incineration bottom ash (IBA), fly ash (FA) and boiler ash (BA), taken from a municipal solid waste incineration (MSWI) plants, as well as a cement-based waste (CBW) from construction demolition wastes. The hypothesis was that these MW would provide trace elements (TEs) deficient in the organic fraction of municipal solid waste (OFMSW), and offer moderate alkalinity to prevent reactor acidification of mesophilic anaerobic digestion of the OFMSW. The control and operation of batch biomethane potential (BMP) reactors and continuous stirred tank reactors (CSTRs; single-stage and two-stage reactors), was studied under different feeding regimes, different organic loading rates and hydraulic/solid retention times, in order to determine potential benefits of mineral waste amendments and aqueous trace metal supplements on anaerobic digestion efficiency, methane productivity and process stability.
Co-digestion of different solid MW and organic wastes in single-stage CSTR using a liquid-recycled feeding method (LRFM) enhanced process stability (pH of 6.8 – 7.2), increased methane production by 25 - 45%, and yielded 450 – 520 mL CH4/g VS (near to the theoretical maximum) compared to the control. Whereas draw-and-fill feeding method (DFFM) also enhanced digestibility but to a lesser degree. Pre-treatment of the OFMSW with the MW at 37oC improved substrate hydrolysis, and enhanced the performance and stability of the DFFM digestion processes further to values similar to those of LRFM reactors. Amending two-stage CSTRs with aqueous MW extracts provided the reactors with the necessary trace elements deficient in the OFMSW, maintained alkalinity and pH, and hence enhanced hydrogen/methane production and processes stability of both acidogenic and methanogenic reactors.
Amendments of IBA, BA and CBW provided trace metals that supported anaerobic digestion processes without adverse effects; however, the metals released from FA provided much lower enhancement of the digestion processes, as some trace metal concentrations were within the toxic range for methanogenic processes.
To elucidate and compare the effect and importance of commercial TE supplementation and substrate co-digestion techniques in improving organic waste anaerobic digestion, especially for the single-stage reactors with high organic loading rates, different CSTR feed compositions were studied. Different feedstocks were investigated including synthetic organic waste (SOW), SOW supplemented with TE, SOW supplemented with wheat straw (WS) and
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SOW supplemented with WS and TE. Results showed that high methane yields (450 - 550 mL/g VS), higher microbial numbers and process stability at higher OLRs, were achieved in all reactors having TE supplementation compared to the equivalent reactors without TE supplementation.
From analysis of molecular microbial data, the effect that different feeding methods, reaction times and WS co-digestion had on reactor performance was found to be associated directly with microbial community selection and stability. Different feeding regimes altered the microbial communities; Methanoculleus (hydrogenotrophic) and Methanosaeta (acetoclastic) were the most abundant methanogenic genera in the LRFM reactors, and the more metabolically versatile Methanosarcina genus dominated under DFFM. Interestingly, at 25% WS supplementation, the Methanosarcina were found to be acetoclastic (based on indicative coenzyme F420 measurements), but with no WS amendment with highest NH3-N levels the F420 values indicated a predominantly hydrogenotrophic metabolism. These results suggest that, WS co-digestion reduced biological stress on the anaerobic community by reducing the net concentration of ammonia in the feedstock
Rapid aqueous mineralisation of carbon dioxide in a scalable process with brines
Get PDFPhD ThesisAqueous mineralisation is a form of mineral carbonation process that reacts CO2 with
reactants in aqueous phase to produce carbonates that fix CO2 permanently. A target
to reach net-zero CO2 emissions by 2050 has been set, in a bid to control the global
surface temperature rise to within 1.5 °C and slow down the rate of climate change.
Carbon capture and utilisation (CCU) is a portfolio technology that converts captured
CO2 into products (e.g. chemicals, fuels, polymers and construction materials) which
can offset the capture and sequestration costs. CO2 mineralisation processes perform
fundamental advantages with thermodynamically favoured and abundant availability of
feedstock among these CCU techniques.
The aim of this study is to develop a feasible technology to enable the scale-up design
of aqueous mineralisation at optimal processing conditions, to achieve complete
carbonation of the calcium content of the brine. An additional goal was to correlate
processing conditions to morphological and mineralogical properties of the precipitated
carbonates, to aid in scale-up of a process that produces highest value products for
specific industries. Compared with the energy-intensive process of gas-solid
accelerated mineralisation, aqueous carbonation remains an attractive option requiring
milder process parameters, and such processes offer more opportunities for
intensification through chemical additives, catalysts, process integration, use of
alternative energy sources, reactor design, among other innovations.
This thesis presents a strategy to sequester CO2 using alkaline desalination brines.
Desalination brine is an attractive source of calcium and magnesium for mineral
carbonation since the ions are dissolved in the solution which is ready to react with
CO2. An alternative approach to conducting rapid and continuous CO2 mineralisation
process in a tubular reactor is revealed which is favoured for scaling-up for industrial
application. Different basic substances were utilised to synergistically boost CO2
solubility in the brine while neutralising the acidification following precipitation of
alkaline earth metals, and blast furnace (BF) slags, sodium hydroxide and low
concentration of MEA were implemented in this study. Nickel nanoparticle catalyst is
introduced to accelerate the carbonation reaction. Moreover, a three-phase analytical
model is established for the scale-up application. A one-dimensional time-dependent
plug-flow model is developed to determine CO2 gas-to-liquid mass transfer rate,
aqueous solution chemical speciation, fluid pressure, and carbonation efficiency within
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the tubular reactor, as a function of reactor length and residence time, under different
process conditions.
Moreover, a basic solid substance to replace the alkaline solution was developed, and
more importantly, it can be recycled for several cycle usage. Hydrotalcite (HT) treated
as a dechlorination agent rather than buffering the mineralisation reaction, and chloride
ions were removed from the brine, increasing its pH, and then conducted the
mineralisation reaction. It indicates that hydrotalcite can be easily regenerated, and its
memory effect property guarantees high efficiency after several cycles. Gaseous CO2
and Na2CO3 solution were tested as the recharging agents, to replace the chloride
anions from the spent HT interlayers and intercalate with HCO3
- or CO3
2-
, followed by
a calcination process to produce the reusable calcined-HT. Multiple reaction cycles
were carried out to evaluate the regenerative and reusable property.
The results showed that the tubular reactor could achieve full (100%) conversion of
calcium from the brine and CO2 from the gas phase by adjusting the parameters to
optimum conditions for both NaOH and MEA, thus proving to be an efficient process
with high atom economy. Furthermore, calcium conversion efficiency is increased by
about 10% in the present of 30 ppm nickel nanoparticles addition. The model explored
the mass transfer of CO2 across the gas-liquid interface in a Taylor flow reactor that
can predict the speciation, bubble size and other parameters of the outlet during the
reaction in the tubular reactor. The overall mass transfer coefficients were obtained
with various CO2 flowrates and MEA concentrations. Modelled results showed that the
bubble length decreased with higher MEA concentration due to the rapid chemical
reaction. The overall mass transfer coefficients increased with higher CO2 flowrates.
Modelled data are also in agreement with the experimental data. With the benefit of
the model, the ionised species distribution in the carbonation process can be predicted
and that can be used to determine the optimal reactor size for scale up.
Compared to previous studies on brine carbonation using NaOH and MEA as pHbuffering additives, the method of using the solid adsorbent calcined hydrotalcite can
facilitate the regeneration process, likely reducing processing complexity, cost and
energy demand. It was found that the chloride removal efficiency remains over 70%
after five cycles, and calcium utilisation efficiency of the brine carbonation process can
surpass 90%. In addition, the value-added carbonate produced from this process is
pure CaCO3, which can be a commercial product that can offset the operational costs.
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This work indicates technical feasibility of the mineralisation process with alkaline brine
solutions and represents a first step towards developing a scalable technology that can
be used with a variety of brines to achieve sustainable CO2 mineralisation
Living microalgae-textile and cyanobacteria-loofah biocomposites for intensified carbon capture, utilisation and storage
Get PDFPhD ThesisMicroalgae and cyanobacteria have been intensively studied as biological routes for carbon
capture. Conventionally, they are cultivated in suspension within open ponds or enclosed
photobioreactors (PBR); however, these systems suffer from many drawbacks including large
land and water consumption, slow mass transfer rates, and high risk of contamination. This
thesis presents a biocomposite culture system to overcome these disadvantages by immobilising
cells onto solid supports (textiles and loofah sponge) using non-toxic hydrogel and latex-based
binders.
The performance of Chlorella vulgaris (a eukaryote microalga) textile-based hydrogel
top coated biocomposites were tested in semi-batch CO2 absorption tests, resulting in enhanced
CO2 capture. The highest CO2 absorption rate was 1.82 ± 0.10 g CO2 g-1
biomass d-1 from coated
cotton biocomposites, followed by 1.55 ± 0.27 g CO2 g-1
biomass d-1 from uncoated cotton
biocomposites. There was some degradation of the cotton, which could limit operational
lifetime of the biocomposites.
Loofah-based Synechococcus elongatus (prokaryote cyanobacterium) latex-based
biocomposites had CO2 absorption rates of 0.68 ± 0.18 and 0.93 ± 0.30 g CO2 g-1
biomass d-1 for S.
elongatus strain PCC 7942 (PCC) and CCAP 1479/1A (CCAP) respectively; however, cell
outgrowth occurred midway through the trials.
The formulations of synthetic latex binders were adjusted using different styrene/butyl
acrylate blends and a coalescence agent (i.e. TexanolTM), increasing CO2 uptake rates by 14-20
and 3-8 fold for CCAP and PCC relative to their suspension controls. The CCAP biocomposites
lasted in excess of 12 weeks whereas the PCC biocomposites experienced cell leaching after
four weeks.
A simplified techno-economic analysis was conducted, revealing that water and energy
consumption were significantly reduced compared to raceway ponds, flat plate PBRs and
biofilm-based PBRs
Applying Machine Learning to enhance payments systems security
Get PDFPh. D. Thesis.During the last two decades, the economic losses because fraudulent card payment transactions have tripled. The significant percentage of losses is because of fraud on e-commerce
transactions. Nowadays, there is a clear trend to use more and more mobile devices to make
electronic purchases, and it is estimated that this trend will continue in the coming years.
In the card payment scheme, big financial institutions process millions of transactions every
day; thus, they can model the processed transactions to predict fraud. On the other hand,
merchants process a much lower number of transactions, but they have access to valuable
information that they can collect from the devices that users utilise during the transaction.
In this thesis, we propose a series of measures to enhance the security of these two scenarios
based on past transactional data and information collected from the users’ device. Most of
the approaches proposed so far to model processed transactions were based on supervised
Machine Learning techniques. We propose a fraud detection system for card payments based
on an unsupervised machine learning technique; thus, the system may be able to recognise
new patterns of fraud.
On the other hand, we are looking far ahead, and because of the increment of use of mobile
devices to conduct payments, we propose a series of measures to enhance the security of the
mobile payment system. We have proposed a user identification and verification systems
for smartphones. We base the identification and verification systems on motion data, so the
systems will not require any explicit action from users
What is school like? An exploration of the experiences of school from the perspectives of adoptive parents and adopted children
Get PDFD. App. Ed. Psy. Thesis.Most adopted children in the UK today are adopted from Local Authority (LA) care having been removed from their birth families due to trauma, abuse, loss and neglect. The impact of the early adversities is likely to affect the child’s ability to access education. It is important that educational professionals are aware of the potential long-term impact of early adversities on adopted children, and adapt their approach to supporting them. This thesis explores the education of adopted children. It is comprised of three chapters: a systematic literature review, a bridging document and a piece of empirical research.
The systematic literature review focuses on adoptive parents’ experiences of their child’s school. A meta-ethnography was conducted to synthesise five qualitative papers. A model was developed to express the synthesis suggesting sharing information and knowledge and understanding of adoption and pre-adoption experiences facilitated trust between school staff and adoptive parents, and ensured the child’s unique needs were met in the classroom. This also enabled adoption to be made salient within the school curriculum. Furthermore, a greater understanding and acknowledgement of the different types of adoptive families enabled diversity to be discussed in lessons, thus supporting the adopted child to feel included in school and the wider school community.
The bridging document offers commentary on the literature review and the development of the empirical research and discusses my philosophical position, methodological decisions and ethical considerations of the empirical research.
The empirical research aimed to fill the gap in the area of researching educational experiences from the perspective of adopted children. Semi-structured interviews were carried out with three secondary school aged adopted children. Interviews were transcribed and analysed using Interpretative Phenomenological Analysis in order to capture the lived experiences of the participants. Three superordinate themes were identified: Relationships, Adoptive Status and Inclusion. These superordinate themes are discussed in consideration of the findings of the Systematic Literature Review and wider research.
The findings of this research reflect wider research highlighting the importance of relationships with staff and peers in addition to the child’s adoptive status to their sense of self and identity, including the importance of having agency over the disclosure of their adoptive status.
These findings have relevance to Educational Psychologists (EPs) who can support schools to facilitate relationship development, highlighting relational approaches and the positive impact these can have on children’s sense of belonging in school. It is important to raise the profile of adoption in educational psychology research. To date, very little has been written about the role of the EP in relation to adopted children and their experiences of school, and this piece of research adds to this gap in the field
The Human Givens approach : a review of independently published research and an exploration of its application in supporting whole school SEMH practice within a secondary school
Get PDFDAppEdPsy ThesisThe prevalence of Social, Emotional Mental Health (SEMH) difficulties both globally and in the UK is acknowledged to be a growing concern (Mental Health Foundation, 2016). Upward trends in SEMH difficulties experienced by the UK population are said to have been further impacted upon by the current Coronavirus pandemic and young people have been found to be at particular risk of increased levels of ‘mental distress’ as a result of the pandemic (Pierce et al., 2020). Furthermore, the Good Childhood Report 2020 (The Children's Society, 2020), has highlighted that children aged 10-15 in the UK are reporting declining rates of overall life satisfaction and happiness with their: appearance, friendships and school.
Schools have been described as having a ‘central role’ in supporting the mental health and wellbeing of Children and Young People (CYP), with the Department for Education stating that schools should have a consistent, whole school approach to mental health and wellbeing. Educational Psychologists (EPs) are professionals who work to support the mental health and wellbeing of CYP in a variety of ways. The Human Givens (HG) approach has been used as a basis for some EP therapeutic practice and is described as a holistic and practical approach that outlines what CYP, families and communities need to be ‘emotionally healthy’.
The first part of this research systematically reviews existing independently published research in relation to the HG approach. It aims to explore potential outcomes of using a HG approach, to support those engaging in therapy/ intervention in relation to their SEMH. Six papers in total were selected for review and analysed using Thematic Synthesis. Four subgroups of direct benefits to individuals in engaging in HG therapy/ intervention were identified namely; ‘Improved Wellbeing’, ‘Improved Coping Ability’, ‘Increased Connection to Others’ and ‘Receipt of Informed Support’. These subgroups consist of nine themes, which are outlined and explored in more detail. The Systematic Literature Review identified a gap within the current literature in relation to independently published research concerning the HG approach and highlighted recommendations for future research made within existing papers, to explore the possible application of the HG as a whole school approach (WSA) to SEMH.
The Empirical Project utilises Collaborative Inquiry (CI) as a method of working with a group of secondary school staff to develop a WSA to supporting SEMH, based on the HG approach. The process of CI is outlined alongside a description of how the HG approach was applied by participants in their school context, to develop a WSA to supporting SEMH. Abbreviated Grounded Theory was used to analyse the transcript of a focus group with participants reflecting on the HG approach and the process of CI. Elements of the HG approach that may support its use as the basis for a WSA to
SEMH are suggested as; ‘HG as an accessible approach’, ‘HG providing a focus on needs (as opposed to behaviour)’, ‘HG as the basis for individualised action’ and ‘HG as providing a shared wellbeing language’. The Abbreviated Grounded Theory then outlines a framework for use when consulting with schools to develop a psychologically informed WSA to SEMH. This framework relates to both the psychological theory used to underpin the WSA and the process used by school to implement the WSA.
Rose: ‘…we’re a school, we’re children and human beings at the heart of what we do, yet somewhere along the way we’ve lost our way, in terms of what we do, why we’re doing it…
Single cell dynamics in bacterial populations for the production of heterologous proteins
Get PDFPh. D. Thesis.Rising healthcare costs and increased population longevity have urged research and the
development of methods for the production of biopharmaceuticals. A third of the total sale of
biopharma are microbial recombinant products. Recently, a central feature of the microbial
populations in fermenters is that of heterogeneity at single cell level.
Considering the cellular heterogeneity, population level analysis used for bioprocess
optimisation and control is misleading. Individual biological entities, their properties and their
interaction with one another and the environment determine the overall behaviour monitored
at population level. As far as protein production, the cellular variability is important for
industry, because the yield affects the bioprocess’ profitability and viability.
To predict cellular behaviour, cells in balanced growth are required. The fermentation
methods that give balanced growth are batch and continuous. The present thesis investigates
heterologous protein production in E. coli at single cell level. Most measurements at single
cell level to unravel heterogeneity use fluorescence, hence the expression system includes
green fluorescent protein (GFP).
The main areas of this thesis are fermentations characteristics at single cell level in host and
recombinant E. coli at different growth rates on glucose or glycerol substrate. The techniques
used to quantify heterogeneity are flow and image cytometry. This work gives new insights
into the cellular heterogeneity that exists in bioreactors and the extent of which it affects the
bioprocess. Focusing on cellular physiology and metabolism of cells used for recombinant
protein production, this work may further facilitate the use of bacteria as cell factories.
Keywords: Escherichia coli, Single Cell, Flow Cytometry, MicroscopyEPSR
The role of alternative coffee production network actors in creating a climate-resilient producer community in northern Peru
Get PDFPh. D. Thesis.This thesis critically examines climate change adaptation in Peru. By considering the case of the
coffee-growing region of San Ignacio, northern Peru, it seeks to address the following central
research question: “In what ways does participation in alternative trading networks shape
smallholder coffee farmers’ ability to adapt to climate change?” The study draws upon the
Global Production Networks (GPN) analytical framework, in addition to bodies of knowledge
in the arenas of climate change adaptation and voluntary certification standards, in order to
evaluate the power relations, knowledge and practices through which smallholder coffee
farmers in Peru are adapting to challenges associated with climate change. The methodological
approach used in this research is qualitative, drawing on field diaries, ethnographic observations
and farm visits. Fieldwork took place between October 2013 and March 2014 and included
interviews with coffee farmers and co-operative staff members from three different cooperatives, farmer field schools, local and national government representatives and NGOs.
The thesis makes three key contributions. First, it demonstrates how the challenges of climate
change are tackled by coffee producer communities in the context of power relations operating
through contemporary trading networks, neoliberal private standards and civil society projects
on environmental justice. Second, it places lived experiences of the coffee farmers centre stage,
in order to evaluate how environmental and economic risk is, and could be, managed in this
particular sector and in this specific locality. The latter has unique characteristics in terms of the
terrain-, climate- and socio-political-based contexts inherent with a country which is so diverse
and home to so many microclimates. Third, it argues that being embedded in an alternative
trading network benefits farmers’ ability to adapt to climate change through both upgrading and
strategic coupling. However, power dynamics, tensions and knowledge flows within the
network are inhibiting the farmers’ agency and ability to reduce their vulnerability to climate
change, to adopt adaptation practices effectively and ultimately to create a climate-resilient
producer community. It is argued that such tensions, power dynamics and knowledge flows
contributed to the coffee leaf rust crisis in 2012/13. These contributions raise important issues
of interest for production network actors involved in designing climate change adaptations for
– and channelling support to – smallholder coffee farmers, as well as for farmers affected by
climate change in other localitiesESR
Evaluation and application of methodology for omic imputation into genome-wide association studies of complex human traits to infer potential causal mechanisms
Get PDFPh. D. Thesis.To date, genome-wide association studies (GWAS) have been successful at
identifying associations between common genetic variants and complex traits.
However, little is known about the mechanisms by which trait-associated variants
identified through GWAS affect the traits. One method developed to address this
problem is the transcriptome-wide association study (TWAS), in which known
relationships between genotypes and gene expression are leveraged to impute gene
expression levels into GWAS samples. These imputed gene expression levels are
then tested for association with traits to identify potentially causal trait-associated
genes. Here, I investigated a number of ways of improving TWAS to enable the
detection of more trait-associated genes, before extending the TWAS approach to
investigate other omics measurements. First, to identify the best software for
conducting TWAS, a range of packages were compared through application to data
from the Geuvadis and Wellcome Trust Case Control Consortium projects. Overall,
the investigated packages predicted gene expression with similar accuracy and
detected similar expression-trait associations, although some tested a broader set of
genes, so were preferable. Following this, the accuracy with which gene expression
could be predicted from genotype data was investigated by comparing different
statistical modelling approaches using data from the Geuvadis project. Overall, the
expression of most genes could not be predicted accurately using any approach, but
the best estimates were achieved when using approaches that assumed sparsity.
Furthermore, prediction accuracy was improved by increasing sample size and by
carefully matching training and testing data in terms of ancestry and tissue. Finally,
the TWAS approach was extended to investigate the prediction of other omics
measurements from genotype data. By generating prediction models for these omics
measurements and applying these models to publicly available GWAS data, many
associations between omics measurements and complex traits were detected,
improving understanding of the mechanisms underlying GWAS risk lociEconomic and Social Research Counci
Safeguarding young people : an exploratory study of how practice develops
Get PDFDAppEdPsy ThesisA Serious Case Review undertaken by a Local Safeguarding Children Board in England found that adolescent neglect was insufficiently understood by professionals working with children and vulnerable adults. A new practice framework was chosen by the Local Authority to address this finding and is in the process of being implemented through training delivered to all who work within Children’s Services. Research evidence, however, suggests that the transfer of learning from training into practice can be relatively low. Informed by the Serious Case Review and previous research evidence, the aim of this thesis was to consider how the development of safeguarding practices by people working within schools and Further Education setting could be supported.
A systematic literature review explored the question: how is safeguarding training embedded into practice by professionals working with young people? Narrative synthesis of data from six papers revealed tentative findings linked to four themes: Learning, Perception of training effectiveness, Training design, and Organisation. The review highlighted that previous research considering the transfer of training has largely ignored: the agency of human beings; the potential influence of their specific context on their agency and practice; and the social nature of human learning.
Consequently, an empirical study was designed to explore how Designated Safeguarding Leads (DSL) from education settings describe their experience of developing their safeguarding practice. Semi-structured interviews were employed as the means of data generation and analysis was conducted using Interpretive Phenomenological Analysis. Three overarching themes emerged that encapsulate the informants described experience. The findings suggest that the DSL role is challenging and complex, with developments in practice largely attributable to experience and personal motivation. Analysis also indicates that there is a desire for improved training opportunities that incorporate connection with safeguarding colleagues. Findings are discussed with reference to existing literature, and implications for future research and practice are offered