5,858 research outputs found
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Ensuring Access to Safe and Nutritious Food for All Through the Transformation of Food Systems
A Decision Support System for Economic Viability and Environmental Impact Assessment of Vertical Farms
Vertical farming (VF) is the practice of growing crops or animals using the vertical dimension via multi-tier racks or vertically inclined surfaces. In this thesis, I focus on the emerging industry of plant-specific VF. Vertical plant farming (VPF) is a promising and relatively novel practice that can be conducted in buildings with environmental control and artificial lighting. However, the nascent sector has experienced challenges in economic viability, standardisation, and environmental sustainability. Practitioners and academics call for a comprehensive financial analysis of VPF, but efforts are stifled by a lack of valid and available data.
A review of economic estimation and horticultural software identifies a need for a decision support system (DSS) that facilitates risk-empowered business planning for vertical farmers. This thesis proposes an open-source DSS framework to evaluate business sustainability through financial risk and environmental impact assessments. Data from the literature, alongside lessons learned from industry practitioners, would be centralised in the proposed DSS using imprecise data techniques. These techniques have been applied in engineering but are seldom used in financial forecasting. This could benefit complex sectors which only have scarce data to predict business viability.
To begin the execution of the DSS framework, VPF practitioners were interviewed using a mixed-methods approach. Learnings from over 19 shuttered and operational VPF projects provide insights into the barriers inhibiting scalability and identifying risks to form a risk taxonomy. Labour was the most commonly reported top challenge. Therefore, research was conducted to explore lean principles to improve productivity.
A probabilistic model representing a spectrum of variables and their associated uncertainty was built according to the DSS framework to evaluate the financial risk for VF projects. This enabled flexible computation without precise production or financial data to improve economic estimation accuracy. The model assessed two VPF cases (one in the UK and another in Japan), demonstrating the first risk and uncertainty quantification of VPF business models in the literature. The results highlighted measures to improve economic viability and the viability of the UK and Japan case.
The environmental impact assessment model was developed, allowing VPF operators to evaluate their carbon footprint compared to traditional agriculture using life-cycle assessment. I explore strategies for net-zero carbon production through sensitivity analysis. Renewable energies, especially solar, geothermal, and tidal power, show promise for reducing the carbon emissions of indoor VPF. Results show that renewably-powered VPF can reduce carbon emissions compared to field-based agriculture when considering the land-use change.
The drivers for DSS adoption have been researched, showing a pathway of compliance and design thinking to overcome the ‘problem of implementation’ and enable commercialisation. Further work is suggested to standardise VF equipment, collect benchmarking data, and characterise risks. This work will reduce risk and uncertainty and accelerate the sector’s emergence
Growth trends and site productivity in boreal forests under management and environmental change: insights from long-term surveys and experiments in Sweden
Under a changing climate, current tree and stand growth information is indispensable to the carbon sink strength of boreal forests. Important questions regarding tree growth are to what extent have management and environmental change influenced it, and how it might respond in the future. In this thesis, results from five studies (Papers I-V) covering growth trends, site productivity, heterogeneity in managed forests and potentials for carbon storage in forests and harvested wood products via differing management strategies are presented. The studies were based on observations from national forest inventories and long-term experiments in Sweden. The annual height growth of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) had increased, especially after the millennium shift, while the basal area growth remains stable during the last 40 years (Papers I-II). A positive response on height growth with increasing temperature was observed. The results generally imply a changing growing condition and stand composition. In Paper III, yield capacity of conifers was analysed and compared with existing functions. The results showed that there is a bias in site productivity estimates and the new functions give better prediction of the yield capacity in Sweden. In Paper IV, the variability in stand composition was modelled as indices of heterogeneity to calibrate the relationship between basal area and leaf area index in managed stands of Norway spruce and Scots pine. The results obtained show that the stand structural heterogeneity effects here are of such a magnitude that they cannot be neglected in the implementation of hybrid growth models, especially those based on light interception and light-use efficiency. In the long-term, the net climate benefits in Swedish forests may be maximized through active forest management with high harvest levels and efficient product utilization, compared to increasing carbon storage in standing forests through land set-asides for nature conservation (Paper V). In conclusion, this thesis offers support for the development of evidence-based policy recommendations for site-adapted and sustainable management of Swedish forests in a changing climate
Hunting Wildlife in the Tropics and Subtropics
The hunting of wild animals for their meat has been a crucial activity in the evolution of humans. It continues to be an essential source of food and a generator of income for millions of Indigenous and rural communities worldwide. Conservationists rightly fear that excessive hunting of many animal species will cause their demise, as has already happened throughout the Anthropocene. Many species of large mammals and birds have been decimated or annihilated due to overhunting by humans. If such pressures continue, many other species will meet the same fate. Equally, if the use of wildlife resources is to continue by those who depend on it, sustainable practices must be implemented. These communities need to remain or become custodians of the wildlife resources within their lands, for their own well-being as well as for biodiversity in general. This title is also available via Open Access on Cambridge Core
Optical Frequency Domain Interferometry for the Characterization and Development of Complex and Tunable Photonic Integrated Circuits
[ES] Esta tesis aborda la caracterización de circuitos fotónicos integrados (PIC) usando interferometrÃa óptica en el domino de las frecuencias (OFDI). OFDI tiene una implementación razonablemente simple e interroga al dispositivo bajo test (DUT) proporcionando su respuesta en el dominio del tiempo, en la que los distintos caminos ópticos seguidos por la luz se manifiestan en contribuciones que contienen información de posición, amplitud y fase. Junto con un "setup" OFDI construido en nuestros laboratorios y estructuras de test integradas que involucran anillos resonantes, interferómetros, etc., proponemos e implementamos técnicas para obtener parámetros ópticos cruciales tales como el Ãndice de grupo, dispersión cromática, rotación de polarización y pérdidas de propagación en guÃas de onda. También para caracterizar acopladores ópticos. Se realizan evaluaciones directas de fase óptica en diferentes experimentos para, entre otras aplicaciones, caracterizar efectos de calor en chips. En la culminación de la tesis, se aborda la integración conjunta de los interferómetros de OFDI junto con el DUT, concibiéndolo como una estructura de caracterización integrada. El uso de guÃas de onda integradas proporciona una alta estabilidad y adaptación al DUT, además de un mecanismo inherente de compensación de la dispersión. Se realiza un análisis y prueba de concepto experimental caracterizando un "arrayed waveguide grating" en tecnologÃa de nitruro de silicio. Seguidamente, se da un paso adelante proponiendo una arquitectura interferométrica de tres brazos novedosa que permite reducir la complejidad de la medida. Se lleva a cabo una validación experimental amplia usando distintos equipos de laboratorio, acoplamiento horizontal y vertical al chip, y diferentes DUTs en tecnologÃas de nitruro de silicio y "silicon-on-insulator".[CAT] Aquesta tesi aborda la caracterització de circuits fotònics integrats (PIC) usant interferometria òptica al domini de les freqüències (OFDI). OFDI té una implementació raonablement simple i interroga el dispositiu sota test (DUT) proporcionant la seva resposta en el domini del temps, en què els diferents camins òptics seguits per la llum es manifesten en contribucions que contenen informació de posició, amplitud i fase. Juntament amb un "setup" OFDI construït als nostres laboratoris i estructures de test integrades que involucren anells ressonants, interferòmetres, etc., proposem i implementem tècniques per obtenir parà metres òptics crucials com ara l'Ãndex de grup, dispersió cromà tica, rotació de polarització i pèrdues de propagació en guies d'ona. També per caracteritzar acobladors òptics. Es fan avaluacions directes de fase òptica en diferents experiments per, entre altres aplicacions, caracteritzar efectes de calor en xips. A la culminació de la tesi, s'aborda la integració conjunta dels interferòmetres d'OFDI juntament amb el DUT, concebent-ho com una estructura de caracterització integrada. L'ús de guies d'ona integrades proporciona una alta estabilitat i adaptació al DUT, a més d'un mecanisme inherent de compensació de la dispersió. Es realitza una anà lisi i prova de concepte experimental caracteritzant un "arrayed waveguide grating" en tecnologia de nitrur de silici. Seguidament, es fa un pas avant proposant una arquitectura interferomètrica de tres braços nova que permet reduir la complexitat de la mesura. Es du a terme una validació experimental à mplia usant diferents equips de laboratori, acoblament horitzontal i vertical al xip, i diferents DUTs en tecnologies de nitrur de silici i "silicon-on-insulator".[EN] This PhD thesis covers the characterization of complex photonic integrated circuits (PIC) by using Optical Frequency Domain Interferometry (OFDI). OFDI has a fairly simple implementation and interrogates the device under test (DUT) providing its time domain response, in which the different optical paths followed by light manifest in contributions with position, amplitude and phase information. Together with a working OFDI setup built in our laboratory and integrated test structures involving devices such as ring resonators, interferometers, etc., we propose and implement techniques to get crucial optical parameters such as waveguide group refractive index, chromatic dispersion, polarization rotation, and propagation loss. Also, to characterize optical couplers. Direct optical phase assessment is made in different experiments permitting, amongst others, the characterization of on-chip heat effects. In the culmination of the thesis, the co-integration of the OFDI interferometers with the DUT is addressed, conceiving it as an integrated characterization structure. The use of integrated waveguides provide high stability and adaptation to the DUT, as well as an inherent dispersion de-embedding mechanism. It is provided analysis and experimental proof of concept with an arrayed waveguide grating as DUT in a silicon nitride platform. A considerable leap forward is then taken by proposing a novel three-way interferometer architecture, reducing the measurement complexity. Wide experimental validation is carried out using different laboratory equipment, horizontal and vertical chip coupling, and different DUTs in silicon nitride and silicon-on-insulator.Bru Orgiles, LA. (2022). Optical Frequency Domain Interferometry for the Characterization and Development of Complex and Tunable Photonic Integrated Circuits [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181635TESI
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DOUBLE EMULSIONS RELEVANT TO FOOD SYSTEMS: FABRICATION, CHARACTERIZATION, AND APPLICATIONS
Systems of the W/O/W type continue to be of growing interest to food scientists and technologists for two main reasons. First, there is the possibility of preparing a reduced-fat emulsion product by the replacement of a conventional oil-in-water emulsion by the equivalent W/O/W emulsion having a lower actual oil content but a similar in-mouth perceived texture. Second, there is the capability to encapsulate and protect a sensitive hydrophilic bioactive compound. However, it is always a bottleneck to obtain robust formulations using economically viable ingredients and processing operations. To improve its performance for practical applications in food production, efforts have been made to overcome the difficulties. Herein, we examined the impact of crystallizing the oil phase on the ability of W/O/W emulsions to encapsulate and retain a model hydrophilic bioactive. The results showed that the texture and stability of the W/O/W emulsions prepared in this study were highly dependent on their composition. The concentrations of both hydrophilic and hydrophobic stabilizers had to be optimized to produce emulsions that contained relatively small droplets, (initially) had relatively low viscosities, and that were stable to coalescence and phase separation. Our results provide some useful insights into the formulation of double emulsions for the encapsulation of hydrophilic bioactive agents. In addition, two novel applications of double emulsion have been investigated to provide insight for food production market. One is to protect natural color (anthocyanin) from pH-induced color changes, the other one is to study the impact of fat crystallization on the resistance to osmotic stress, which could be a potential for temperature-triggered release
Techno-economic analysis for local hydrogen production for energy storage and services
The energy industry is quickly changing, with more renewable energy technologies emerging
and sustainable sources growing in their capacities, which is slowly reducing the need for
fossil fuel sourced energy supply. But with it come challenges, with energy storage becoming
increasingly more important to help balance the gap between the energy supply and demand.
The interest in hydrogen has accelerated in recent years as it can be used for several end uses,
for example power-to-power, power-to-gas and power-to-fuel. It could therefore potentially
decarbonise several industries, not just the energy sector. For hydrogen produced by
renewables through water electrolysis to become competitive, the issues of low roundtrip
efficiencies, high costs and the need of scaling up a new infrastructure needs to be addressed.
This research project is a collaboration between University of Edinburgh and Bright Green
Hydrogen (BGH). BGH is a non-for-profit company that created and launched the
Levenmouth Community Energy Project (LCEP) in 2014 (operational from 2017) to explore
electrolytic hydrogen’s ability to decarbonise energy supplies. The LCEP consists of: 750 kW
wind turbine, 48 kW roof PV, 112 kW ground PV, 250 kW PEM electrolyser, 100 kW PEM
fuel cell, two 60 kW hydrogen refuellers and a total of 17 hydrogen vehicles of three different
models. This project used the data, information and observations from the LCEP to build an
energy system model that included hydrogen with real-world aspects. The model was used to
explore different ways that the economics and self-reliance for energy of small-scale hydrogen
systems can be improved by conducting a techno-economic analysis on a number of
alterations. The electrolyser control system was improved to help the electrolyser behave more
energy efficiently, components were changed in sizing and a Lithium-ion battery was added
into the model to help optimising the main electrolyser’s performance.
The first novelty of this work was a new electrolyser model that was developed specifically to
account for energy consumption and hydrogen production at low load, which appeared
frequent and significant in this type of system. The model was found to represent the plant
data better than existing ones. One general conclusion from this work was the impact of
operation at low load, which is difficult to avoid at all times and yet should be minimised for
good technical and economic performance.
The second contribution to knowledge in this work is the methods and findings of the technoeconomic
assessment. Several possible improvements were explored to find a balance in
techno-economic performance of the small-scale hydrogen production facility.
It was found that a control system that made adequate use of forecast weather and energy
supply data was critical for effective and efficient use of the electrolyser, without excessive
shutdown time and parasitic loss at times of low energy supply.
In addition, changes in the respective capacities of the components (electrolyser, storage, solar
energy supply) for the same demand could result in significant improvements in economic
performance, and so could the incorporation of batteries within the system in support of the
electrolyser. Batteries helped both electrolyser standby load (to help with grid independence)
and hydrogen production (to improve electrolyser’s output). However, there is a balance
between battery storage size and system benefits.
In the particular case of the LCEP as built, the system struggled to perform well while it had
two end uses (energy storage for buildings and fuel for vehicles) without more energy and
hydrogen supply. Also, the main electrolyser was oversized for its needs, resulting in poor
capacity utilization and high parasitic load. But a significantly smaller electrolyser with
sufficient storage had a notable technical benefit to the system.
Finally, there were several adjustments that could lead to a technically well-performing smallscale
hydrogen system, but none that made it economically feasible. Capital costs, operating
costs, maintenance costs, major replacement costs and durability of components are still major
factors that need to be addressed for hydrogen at this scale to be feasible.
However, this work clearly identified required areas of progress to achieve economic viability
without subsidies, in particular, improving the longevity of the electrolyser and fuel cell stacks
would alone enable a positive Net Present Value. In addition, recent and ambitious policy
decisions and more widely deployed demonstration projects can stimulate volumes of
productions of these components, and the significant cost reductions that these would allow
Preparación de fibras y otros materiales de carbono para adsorción de CO2 en post-combustión
Finalmente, otro carbón activo, GAL, y una tela de carbón activada, CAD, se sintetizaron por activación quÃmica con ácido fosfórico de lignina y tela vaquera. Los distintos materiales se han caracterizado utilizando diversas técnicas y procedimientos, tales como adsorción-desorción de N2 a -196 ºC, adsorción de CO2 a 0 ºC, XPS, DTP y SEM. Para la evaluación de los materiales en la aplicación de interés se han realizado experimentos de adsorción, en equilibrio y en columna lecho fijo, en un rango amplio de condiciones experimentales e incluyendo las temperaturas, presiones y composiciones tÃpicas de los procesos de post-combustión. También se ha estudiado el potencial de regeneración de varios de los materiales mediante ciclos de adsorción-desorción.
Los resultados obtenidos han sido muy prometedores, alcanzándose capacidades de adsorción y selectividades comparables a las de otros materiales complejos incluso a temperaturas elevadas. Cabe destacar, además, que la presencia de H2Ov, o bien no afecta de manera significativa al rendimiento de los materiales analizados; o bien, podrÃa actuar de forma sinérgica y mejorar su capacidad de adsorción. Por otro lado, se ha conseguido profundizar y establecer relaciones muy interesantes entre las caracterÃsticas estructurales del material (porosidad, quÃmica superficial, morfologÃa, etc.) y la capacidad de adsorción en diferentes condiciones; y se han calculado diversos parámetros termodinámicos y cinéticos importantes para futuras etapas de diseño.La adsorción de CO2 sobre sólidos porosos en sistemas de post-combustión constituye una de las alternativas prioritarias para reducir y estabilizar su concentración a los niveles exigidos. Entre los adsorbentes estudiados, los materiales de carbono resultan especialmente interesantes debido al carácter hidrofóbico (mayor estabilidad en presencia de humedad) y menor calor de adsorción (facilidad de regeneración) que generalmente presentan. En el contexto de desarrollo sostenible, su obtención a partir de residuos biomásicos conllevarÃa beneficios sinérgicos adicionales, al capturarse CO2 y valorizarse un residuo simultáneamente. Sin embargo, las condiciones tÃpicas de las corrientes de post-combustión suponen un verdadero reto y sus capacidades de adsorción y selectividades aún deben ser mejoradas para su implementación real. Ambos parámetros están intrÃnsecamente relacionados con las propiedades fisicoquÃmicas y estructurales del material, por lo que los esfuerzos se están orientando a clarificar su influencia, asà como a desarrollar nuevos materiales carbonosos con las caracterÃsticas óptimas.
En esta lÃnea, el objetivo principal de esta Tesis Doctoral ha sido caracterizar y evaluar una serie de materiales de carbono diferentes como adsorbentes de CO2 en condiciones de post-combustión. En concreto, se han preparado seis materiales de carbón a partir de cuatro tipos de residuos lignocelulósicos con alto potencial de valorización, abundantes y de bajo coste: fibras de carbón por electrospinning, FCL, y un carbonizado granular, GCL, a partir de lignina Alcell®; dos carbones activos, GAS y GAWBa, por activación fÃsica de hueso de aceituna y residuo de aglomerado de madera, respectivamente. GAWBa fue, además, impregnado con acetato de bario en una etapa posterior para dotarlo de un cierto número de grupos básicos superficiales
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