Dissertations / Theses on the topic 'Biocrust'

Le zone aride sono tra le aree più sensibili al cambiamento globale e i modelli prevedono un incremento della loro superficie nei prossimi decenni. La morfologia del terreno ha un ruolo chiave nella distribuzione dell'acqua e delle sostanze nutritive nelle zone aride e nella determinazione della loro composizione. Questi ambienti sono composti da vegetazione e suolo nudo, molte volte colonizzato da biocroste, che si prevede subiranno cambiamenti nella composizione. Il telerilevamento è stato evidenziato come uno strumento importante per il monitoraggio delle zone aride. Si tratta di un approccio molto efficace in termini di costi per identificare gli hotspot di biodiversità, prevedere i cambiamenti nella loro composizione e valutare le relazioni che tali cambiamenti hanno con la morfologia del terreno. Utilizzando specifiche tecniche di analisi delle immagini a seconda del caso di studio, il telerilevamento si è dimostrato utile per il monitoraggio di zone aride ben differenziate, ma non in caso di composizione mista. Pertanto, l’obiettivo principale di questa tesi di dottorato è stato quello di studiare come la composizione eterogenea e il funzionamento delle zone aride sono influenzati dalla morfologia del terreno integrando l’utilizzo di diversi sensori di telerilevamento e piattaforme. Sono stati utilizzati dati provenienti da immagini RGB, termiche ad infrarosso (TIR), multi- e iperspettrali ad altissima risoluzione spaziale acquisite in laboratorio e in campo utilizzando piattaforme aeree, UAV e stazionarie. Sono stati definiti i seguenti obiettivi specifici: - Valutare se le tecniche Structure from Motion (SfM) possono essere utilizzate in zone aride dalla superficie complessa per ricavare la morfologia del terreno da immagini UAV; - Sviluppare una tecnica riproducibile per mettere in relazione le azioni antropiche con i cambiamenti nello stato di salute delle comunità vegetali in ecosistemi aridi utilizzando tecniche di analisi object-based; - Valutare se l'eterogeneità spettrale dei licheni può essere utilizzata per stimare la loro α-diversità utilizzando immagini iperspettrali; - Sviluppare una metodologia per valutare l’influenza della morfologia del terreno sulla distribuzione delle biocroste in zone aride utilizzando informazioni acquisite esclusivamente mediante UAV; - Valutare se le immagini TIR possono essere usate per stimare l'umidità del suolo in zone aride eterogenee. Questa tesi di dottorato comprende una valutazione delle tecniche SfM a diverse scale e della loro applicabilità a diversi livelli. Affronta lo sviluppo di una nuova metodologia per monitorare la vegetazione in un ecosistema dipendente dalle acque sotterranee, dove la loro salute è fondamentale per il funzionamento dell'ecosistema. Inoltre, l'utilizzo di immagini iperspettrali acquisite a distanza ravvicinata ha permesso di stimare la α-diversità dei licheni che formano le biocroste utilizzando la loro diversità spettrale. Questo ha portato ad una migliore comprensione del comportamento spettrale delle biocroste a seconda della loro composizione, permettendo di sviluppare una metodologia per produrre mappe accurate della copertura del suolo in un ecosistema eterogeneo e di relazionare l'effetto della morfologia del terreno sulla composizione degli ambienti aridi.
Drylands are among the most sensitive areas to actual global change and their cover will increase in the next decades. Terrain has a key role in the distribution of water and nutrients in drylands and shaping their composition. These environments are composed by vegetation and bare soil, many times colonized by biocrusts, which are expected to suffer compositional changes. Remote sensing has been highlighted as an important tool for dryland monitoring. It is a very cost-effective approach to identify biodiversity hotspots, predict changes in their composition, and to evaluate the relationships these changes have with the terrain. Using the proper image analysis according to the study case, remote sensing has proved to be useful for monitoring well differentiated drylands, but not when dryland components are mixed. Thus, the main aim of this dissertation was to study how heterogeneous dryland composition and functioning is affected by the terrain using different multiple remote sensing sensors and platforms. Data from very high spatial resolution RGB, thermal infrared, multi- and hyperspectral imagery, retrieved in the laboratory and in the field using airborne, UAV and stationary platforms were used. The next specific objectives were set: - Evaluating whether SfM techniques can be used in drylands with complex surfaces to derive their terrain from UAV imagery; - Developing a reproducible technique to relate human actions to changes in the health of dryland scarce vegetation communities by using object-based image analysis; - Testing whether the spectral heterogeneity of lichens can be used to estimate their α-diversity using hyperspectral imagery; - Developing a methodology to evaluate the control that terrain has on dryland biocrusts’ distribution using information solely retrieved from UAV; - Testing if TIR imagery can estimate soil moisture in heterogeneous drylands. This PhD thesis comprises an evaluation of SfM techniques at different scales and their applicability at different levels. It also comprises a novel methodology to monitor vegetation in a ground-water dependent ecosystem, where their health is key for the ecosystem’s functioning. Moreover, the application of close-range hyperspectral imagery allowed to estimate the α-diversity of biocrust-forming lichens using their spectral diversity. This led to a better understanding of the spectral behaviour of biocrusts depending on their composition and allowed to develop a methodology to produce accurate maps of land cover in a dryland ecosystem of heterogeneous composition and to relate the effect of terrain atrributes on dryland composition.

Biocrusts and the ecosystem services they provide are becoming more susceptible to fire as exotic annual grass invasions facilitate the spread of desert wildfires. Further, precipitation patterns across the western United States are predicted to change over the next century, and have the potential to dramatically influence fire regimes and the recovery of burned biocrusts. Despite these changes to desert fire and precipitation cycles, our understanding of post-fire biocrust recovery is limited, especially regarding the first two years after fire. To investigate biocrust recovery, we created burn manipulations (i.e., unburned and burned) and tracked crust form and function over two years in one cold and one hot desert ecosystem (UT, USA). We evaluated the entire bacterial community, but focused on Cyanobacteria species that confer soil stability and N fixation capabilities to biocrusts. Specifically, we quantified shifts in biocrust bacterial community composition using target metagenomics of 16S rDNA; monitored biocrust moss and lichen cover; measured N fixation potential; and assessed soil infiltration rates and soil stability. We found little evidence that biocrust form or function recovered from fire within two years. Based on pyrosequencing results, fire altered biocrust community composition in interspace and shrub biocrusts. Cyanobacteria species were almost completely eliminated by fire, constituting 9-21% of unburned plots and less than 0.01% of burned interspace and shrub biocrust communities. Based on cover estimates, no lichen or moss species survived the fire or recovered within two years. N fixation potentials decreased by at least six-fold in burned interspace biocrusts, representing a reduction in soil N inputs into already N-limited desert soils. Soil infiltration rates also drastically declined in burned biocrusts and remained depressed, but only remained depressed for one year. To investigate the interactions between biocrust recovery, fire, and precipitation, we nested precipitation treatments manipulating the amount of monthly rainfall (i.e., ambient, plus 30% and minus 30%) within burn treatments during the second year. Soil NH4+ was the only parameter to be affected by precipitation, and exhibited a positive relationship with precipitation magnitude at the end of one year. Our results demonstrate that fire is a strong destabilizer of the bacterial components of biocrust communities and that the ecosystem services provided by crusts recover at different rates, with N dynamics recovering more slowly than soil ecohydrology.

Les gisements de Terres Rares (REEs) d'argile à adsorption ionique sont l'un des principaux réservoirs de REEs dans le monde. Ils sont principalement distribués dans le Jiangxi, le Guangdong et d'autres provinces du sud de la Chine. Au cours des dernières décennies, leur production a causé de graves dommages environnementaux et laissé une grande superficie de résidus miniers, tels une menace constante sur l'environnement. Les principaux problèmes de ces résidus sont une mauvaise structure physique, une fertilité extrêmement faible, une pollution et une toxicité élevées. Ces facteurs défavorables entravent la colonisation des organismes et la restauration des services écosystémiques. Par conséquent, la restauration de la structure et des fonctions du sol et de l'écosystème sont une question majeure. La succession naturelle et la phytoremédiation sont des stratégies de gestion de ces résidus miniers. Le processus de formation du sol et le mécanisme de succession écologique dans ces différentes stratégies sont différents. Compte tenu du coût et du temps nécessaires, la comparaison de ces approches est essentielle. Le but de cette thèse est d'étudier : 1) la structuration et l'évolution des fonctions du sols et des écosystèmes de stériles miniers en succession naturelle; 2) les effets de différentes stratégies de phytoremédiation et 3) l'évaluation comparative de la qualité des sols et de l'environnement écologique dans le cadre de la succession naturelle et de la phytoremédiation. (1) Dans la succession naturelle, les fonctions pédologiques et écologiques progressent considérablement au fil du temps. En outre, nous avons constaté qu'il y avait trois modèles d'évolution complètement différents au début de la succession (sol nu, croûtes biologiques et végétation vasculaire) et que la relation entre eux est évolutive. La genèse d'agrégats du sol, en particulier les macroagrégats biogéniques, impacte l'accumulation de nutriments, le comportement des REEs et la diversité des micro-organismes. (2) De plus, les macroagrégats associés aux croûtes biologiques (BC) et associés aux racines de plantes vasculaires (RS) échantillonnés sur des résidus de REEs se révèlent être différents. Les modalités BC et RS avaient des concentrations en nutriments significativement plus élevées. La concentration de REEs la plus élevée a été observée pour BC, tandis que la plus faible a été observée pour RS, ce qui suggère que les REEs se redistribueraient entre différents horizons selon la restauration biotique. Fait intéressant, les micro-organismes autotrophes étaient concentrés dans BC, tandis que les bactéries rhizosphériques hétérotrophes favorisant la croissance des plantes étaient concentrées dans RS. Ces résultats montrent que le mécanisme et l'efficacité de la restauration entre les différentes approches sont significativement différents. (3) Différentes stratégies de phytoremédiation ont été testées par des expériences de terrain. Par rapport aux résidus nus, l'ajout d'amendement induit une augmentation significative de la fertilité chimique et favorise la formation de macroagrégats, réduisant ainsi la disponibilité des REEs. De plus, les modifications introduisent de nouvelles bactéries (p. ex. Burkholderia), qui modifient certaines caractéristiques biologiques des résidus et favorisent la circulation des éléments nutritifs. Nos expériences sur le terrain ont prouvé l'efficacité et la durabilité des amendements que nous avons conçus, mais cet effet semble avoir disparu à 16 mois. En conclusion, nos recherches montrent que la nature, en tant qu'« ingénieur », améliore sans interruption la qualité du sol et de l'environnement écologique, tandis que les efforts de phytoremédiation, s'ils améliorent considérablement la fonction du sol et de l'environnement écologique, ont un effet qui s'affaiblit avec le temps, ce qui nécessite une observation à plus long terme
Ion-adsorption REE deposits are one of the main reservoirs of REEs worldwide, mainly distributing in southern China. In the past decades, the production of REEs has caused serious environmental damage and left over a large area of tailings which continuously threaten the surrounding environment. The main obstacles for ecological restoration of such tailings are poor physical structure, low nutrients, high pollution of REEs and Al. These unfavourable factors hinder the colonization of organisms and the restoration of ecosystem services. Therefore, how to restore the structure and function of soil and ecosystem has become a major issue. Natural succession and phytoremediation provide an option for restoration of mine tailings. However, so far less is understood in terms of the mechanisms of soil formation and ecological succession of REE tailings under different strategies. Therefore, the objectives of this thesis are to: 1) study the evolution mechanism of structure and function of tailing soils and ecosystem in natural succession; 2) study the restoration effects of various phytoremediation strategies; and 3) assess the soil and ecological environment quality under natural succession and phytoremediation. The main findings are as follows. (1) In natural succession of a 15-year chronosequence, soil and ecological functions are significantly increasing over time. There are three completely different evolution patterns (i.e. visual bare, biocrust and vascular vegetation) in the early stage of succession. The evolution between biocrusts and vascular plants occurs from the initial mutual promotion to the later competition. The formation of large aggregates (> 0.25 mm) is mainly controlled by the electrostatic interaction of minerals and biological activities, which improves the diversity of microorganisms and accumulation of nutrients, and controls the migration of REEs. (2) The macroaggregates associated with biocrusts (BC) and with vascular plant root soils (RS) show different morphologies, that is, longitudinal stratification of biocrust and interlacement within the rhizosphere. Both BC and RS are significantly enriched in nutrients. The highest REE concentration is observed in BC while the lowest is found in RS, suggesting that REEs could be redistributed among different horizons by biotic processes. Interestingly, autotrophic microorganisms are more concentrated in the BC, while heterotrophic rhizosphere growth-promoting bacteria are preferentially distributed in the RS. These results show that, although in the same site, the mechanism of soil formation and recovery of soil function under different evolution patterns are quite different. (3) In consideration of time and efficiency, different phytoremediation strategies (i.e. amendment and plantation of pioneer plant Miscantus sinensis and commercial grasses) were conducted by a plot experiment. Compared with bare tailings, the addition of amendment induces a significant increase in nutrients, promotes the formation of macroaggregates, and reduces the availability of REEs. In addition, phytoremediation introduces nitrogen fixing bacteria (e.g. Burkholderia), which change the biological characteristics of tailings and promote nutrient cycling. Our results have proved the effectiveness and sustainability of the amendment input. Nevertheless, the plant effect is not significantly visible within only a 16 month-experiment in this study. In conclusion, this research shows that nature, as an “engineer”, is uninterruptedly improving the soil and ecological environment quality, while phytoremediation efforts can significantly enhance the soil and ecological environment function but the effect weakens with time, which requires longer-term observation

This thesis describes fractional distillation as an upgrading method for improving the quality of hydrothermal liquefaction (HTL) biocrude as a green-based biofuel. Firstly, as a part of the biomass to fuel pathway, aqueous phase recycling in the HTL process increased the yield of biocrude production and reduced the nitrogen content. Secondly, fractional distillation improved the biocrude quality (e.g., lower nitrogen content, viscosity, etc), co-processing ability (with conventional fuels) and improved stability during storage. Finally, the learnings from fractional distillation facilitated more accurate process modelling of biocrude assisting biocrude application in the current fossil fuel supply chain.

Drylands represent the planet's largest terrestrial biome and evidence suggests these landscapes have large potential for creating feedbacks to future climate. Recent studies also indicate that dryland ecosystems are responding markedly to climate change. Biological soil crusts (biocrusts). soil surface communities of lichens, mosses, and/or cyanobacteria. comprise up to 70% of dryland cover and help govern fundamental ecosystem functions, including soil stabilization and carbon uptake. Drylands are expected to experience significant changes in temperature and precipitation regimes, and such alterations may impact biocrust communities by promoting rapid mortality of foundational species. In turn, biocrust community shifts affect land surface cover and roughness-changes that can dramatically alter albedo. We tested this hypothesis in a full-factorial warming (+ 4 degrees C above ambient) and altered precipitation (increased frequency of 1.2 mm monsoon-type watering events) experiment on the Colorado Plateau, USA. We quantified changes in shortwave albedo via multi-angle, solar-reflectance measurements. Warming and watering treatments each led to large increases in albedo (> 30%). This increase was driven by biophysical factors related to treatment effects on cyanobacteria cover and soil surface roughness following treatment-induced moss and lichen mortality. A rise in dryland surface albedo may represent a previously unidentified feedback to future climate.

Hydrothermal Liquefaction (HTL) has been the cornerstone of research in biofuels production with the recent advances utilising algae biomass as biofuels precursor. HTL technology offers a more cost-effective pathway in transforming algae into biofuel than other technology (such as pyrolysis and torrefaction), as it obviates the drying step. However, one of the main challenges in implementing algae-derived biocrude oils as transport fuels is the higher nitrogen content (5 – 7 wt%) than fossil fuels (~0.3 – 0.5 wt%). Nitrogen content in the biocrude oils is associated with the nitrogenous compounds (such as pyrazines) formed through carbohydrates and proteins reactions. To date, the chemistry understanding of nitrogenous species formation under HTL conditions is not well-established. The objective of this thesis is to study and analyse nitrogenous distribution in reaction products emerging from HTL involving carbohydrates and proteins. Arising from the foregoing, the research develops alternative reaction pathways to pyrazine formation to achieve an elevated understanding of the chemistry of nitrogenous species in biofuels. Included is a quantitative estimate of kinetic parameters, such as rate constants and activation energy. One key outcome of this research is the development of an analytical methodology for the quantitative estimation of pyrazines in a product mixture of HTL of carbohydrates and proteins. Scientific findings presented in this chapter provide a deep understanding of the nitrogenous species, including reaction pathways, nitrogen distribution, and kinetic parameters of sugars – alanine and sugar – ammonium interactions under HTL conditions. The impacts of these findings on biofuel industries are outlined and several recommendations for future research in sustainable biofuel development and production are proposed.

This thesis explored hydrothermal co-liquefaction of algae and bagasse with a focus on the reduction of nitrogen and sulphur contents in the biocrude. Surrogate fuels mimicking the nitrogen and sulphur contents of algae biocrude were developed and tested in an engine to understand their effect on engine performance and emissions. This work provided a better understanding of the combustion of N-containing fuels and an insight into the future use of algal biocrude in combustion engines.

The demand of renewable fuels is increasing. Catalytic Fast Pyrolysis is a growing technology that could supply with high quality bio crude that can be used in the already existing infrastructure. The process of choice in this paper to implement this technology is insitu circulating fluidized bed using saw dust as feed. Two cases are designed and then modelled in ASPEN Plus. The first case uses steam as fluidizer and the second uses recycled pyrolysis gas as fluidizer. Both cases are found to be self-sustainable with biomass as the only energy source. According to the parameter study, this is only true for biomass feed up to 40% moisture content.
Efterfrågan om förnyelsebara bränslen ökar. Catalytic Fast Pyrolysis är en växande teknologisom skulle kunna förse med bio-crude av hög kvalité för att användas med dagensinfrastruktur. Den process som valdes för att implementera denna teknologi är in-situcirculating fluidized bed med sågspån som inmatning. Två fall blev utformade och sedanmodellerade i ASPEN Plus. Det första fallet använder sig av ånga som flödare och andrafallet använder sig av återvunnen pyrolysgas. Båda fallen var självförsörjande med endastbiomassa som energikälla. Enligt parameterstudien stämmer detta endast för biomassa medmindre än 40% fuktinnehåll.

This work tackles a feasibility analysis on the electrocatalytic hydrogenation of palmitic acid as model compound for the interested hydrothermal liquefaction's (HTL) biocrude. It represents an upgrading study in order to produce high quality bio-oil or even biofuels. The aim was to confirm the possibility to attack this very unreactive molecule electrochemically, performing the target reaction of hydrogenation in lab-scale systems. Furthermore, also a qualitative analysis on the product and on the possible reaction scheme has been done. Due to the lack of literature, further study must be done in order to confirm exactly the reaction pathways and the specific products, as well as to investigate the kinetics and the efficient parameters of the reaction. HTL is a promising process for the treatment of wet biomass without costly and energy expensive pre-treatments. The derived biocrude is an important source of energy. On the other hand, electrocatalytic processes for bio-based chemicals upgrading rely on a very high energy efficiency and a good versatility in term of space, cost and easy implementation, as well as low impacts due to the possible integration with delocalised renewables energy sources. The aim of this study was born with the necessity to integrate these two processes in order to have a feasible and cost-effective processes for the direct production of biofuels.

Extraction of oil and gas in Utah’s Uintah Basin results in large quantities of wastewater, or produced water, with nutrients and residual organic chemical that represent a significant resource for producing energy-related and value-added products. Produced water was obtained as a biomass producing nutrient source from industries operating in Utah’s Uintah Basin. Within the Uintah Basin (defined as Uintah and Duchesne Counties within Utah) approximately 93 million barrels of water were produced in 2013 while only 11% of the water was disposed of through evaporation, with the national average at 2%. The rest is reinjected into the subsurface. The goal of this project was to design a system that utilizes produced water as a nutrient source for growing microalgae biomass in a biofilm form using a Rotating Algal Biofilm Reactor (RABR). The biomass would then be harvested and converted into biocrude oil using hydrothermal liquefaction (HTL). The objectives were to (1) cultivate biomass on produced water, (2) optimize the reactor to reduce energy costs to operate while increasing biomass productivity, and (3) increase feedstock quality for HTL. The RABR was constructed out of polystyrene disks, and experimentation was carried out to optimize rotational speed of the reactor. Two strains of algal biomass were identified as biofilm formers and grown using produced water as the nutrient source. The biomass was then utilized as a HTL feedstock that gave an average yield of 34.5% ash free dry weight.

This Ph.D. project has been addressed to evaluate the potential of microalgal technology for biofuel production. Different steps of the process, as well as technologies and concepts have been analyzed experimentally and by process simulations in order to assess the sustainability of the production of biofuel from microalgae. An experimentation work on microalgae cultivation in untreated wastewaters is reported, including the selection of the optimal wastewater process stream, the nutrients removal efficiencies and the removal rates. Also, the effects of temperature, day/night irradiation and bacterial competition in steady-state biomass production are evaluated in order to integrate both technologies. Downstream processing has been investigated with respect to anaerobic digestion and hydrothermal liquefaction (HTL) of microalgae biomass. The production of biogas is evaluated using whole and de-oiled microalgae, as a function of inoculum typology and biomass concentration, and the effect of the solvent used for oil extraction is tested. For HTL, the recovery and reuse of the water process is investigated, by recycling it into the HTL system, testing the effects of temperature and the number of recycles on the product yields. An energy analysis of the entire process, considering several process routes and conditions is presented to verify and optimize its energy profits with respect to EROEI, and eventually a process which is energetically self-sufficient is proposed. Finally a techno-economic analysis of a large-scale plant of biocrude is reported, where data from experimental results and process simulations are used to calculate the oil selling price to achieve revenues from the production of biofuel from microalgae.
I biocarburanti provenienti da biomassa microalgale sono considerati come una delle alternative migliori e più a breve termine per produrre energia pulita. Le microalghe sono microorganismi capaci di convertire l’energia solare in energia chimica che può essere sfruttata come combustibili di diverse tipologie sia liquida sia gassosa. L’obiettivo della ricerca presentata in questa Tesi é di valutare il potenziale della tecnologia per la produzione di olio da microalghe, analizzando diverse alternative e concetti sia in modo sperimentale che tramite simulazioni del processo. Il Capitolo 1 é una discussione introduttiva sulla situazione mondiale delle microalghe, recenti studi e gli ultimi risultati riportati su questa tecnologia. Dal punto di vista sperimentali, nei Capitoli 2 e 3 di questa tesi si sono approfonditi, la coltivazione di microalghe in acque reflue e la capacità che presentano alcune specie di microalghe di crescere in acque reflue non trattate, verificata con la microalga Chlorella protothecoides. La crescita é stata valutata in acque provenienti da diversi step del di trattamento delle acque, per selezionare la stream ottimale per la crescita delle microalghe. Inoltre, é stata testata la efficienza nella rimozione di nutrienti e i tassi di rimozione in acque reflue reali. Nel Capitolo 2 si riportano anche la produzione di biomassa in stato stazionario con alimentazione continua del effluente. Nel Capitolo 3 sono stati studiati gli effetti della temperatura, l’irradiazione in ciclo giorno/notte e la competizione batterica sulla crescita di C. protothecoides, e la rimozione dei nutrienti con l’obiettivo d’integrare entrambe tecnologie in un approccio realistico. É stato infine proposto uno schema modificato dell’impianto di depurazione. Il Capitolo 4 presenta il lavoro sperimentale per la valutazione della capacità di produzione di biogas da microalghe e le loro velocità di degradazione nel processo di digestione anaerobica: sono state testate diverse condizioni come la tipologia del’inoculo batterico e la concentrazione della biomassa algale all’inizio delle prove. Inoltre, questo capitolo riporta anche la ricerca nel recupero del contenuto energetico dalla biomassa residua dopo l’estrazione di olio, dimostrando che il metodo di estrazione dell’olio é un fattore importante. La produzione di biogas e sua corrispondente frazione di metano sono stati testati considerando l’effetto della miscela di solvente usato nella estrazione, e i risultati sono stati confrontati con quelli della biomassa microalgale prima della estrazione. Il Capitolo 5 é focalizzato sulla conversione di biomassa mediante il processo di liquefazione idrotermica (HTL) che viene svolto a temperature tra 200 C e 375 C (la pressione é quella necessaria per mantenere l’acqua in stato liquido), ed é caratterizzato da alte rese. Tuttavia, uno dei sottoprodotti é una fase acquosa con alto contenuto di componenti organici che deve essere trattata adeguatamente per evitare ulteriori costi. In questo capitolo si riporta il lavoro sperimentale svolto con l’obiettivo di recuperare e riutilizzare l’acqua di processo mediante un riciclo nel sistema stesso. Inoltre si é misurato l’effetto della temperatura e del numero di ricicli nelle rese di produzione di olio, gas, residuo solido e la fase acquosa e la composizione dei prodotti. Nel Capitolo 6 si riporta l’analisi energetica del processo per la produzione di biocrudo: lo studio é stato svolto considerando diverse tipologie e condizioni di processo, i quali sono stati modellati e simulati dal simulatore di processo Aspen PlusTM, col fine di verificare e ottimizzare i profitti energetici rispetto all’analisi del EROEI, e di proporre un processo energeticamente autosufficiente. Dei diversi processi studiati per ottenere energia della biomassa quello che utilizza la combustione di biomassa dopo estrazione dell’olio é risultato il più favorevole in termini energetici. In particolare, due casi di questo processo sono stati confrontati con un caso base, variando la provenienza dei requisiti energetici (calore ed elettricità), fornendoli sia da fonti esterne che dal processo steso. In ultimo, nel Capitolo 7 si riporta una valutazione tecnica di un impianto per la produzione di biodiesel da microalghe in cui si propone una nuova configurazione della sezione di crescita, un fotobioreattore ibrido, il Closed Pond Reactor (CPR). L’intero processo é stato simulato Aspen PlusTM e ottimizzato per ottenere i migliori benefici in termini energetici. La progettazione e il dimensionamento delle attrezzature tecnologiche sono stati effettuati per ottenere una stima realistica dei costi, considerando sia CAPEX (costi di capitale) e OPEX (costi operativi). Nell’analisi economica si é valutata, la redditività del processo su scala industriale e sono stati calcolati i prezzi di vendita corrispondenti dell’olio e del biodiesel necessario per rendere la produzione economicamente sostenibile.

This project modelled a thermal liquefaction industrial facility for biofuel production from sugarcane bagasse using the process modelling software ASPEN Plus. Techno-economic models of liquefaction, pyrolysis and gasification processes were completed to assess the comparative feasibility of these thermochemical biofuel production processes. Model liquefaction biocrudes, were developed in ASPEN Plus using simulated distillation data and this method's utility in modelling biocrudes was validated.

This thesis is a comparative study on thermochemical conversion of biomass and waste feedstocks into fuels and is divided into two streams. The first investigates the use of wet microalgae feedstocks, using hydrothermal liquefaction (HTL), to produce biocrude. The second stream explores the use of dry waste tyre feedstocks using Green Distillation Technology (GDT), a modified pyrolysis process, to make tyre oil. An experimental investigation of the physicochemical properties of biocrude oil and tyre oil is made. Finally, the impact of the both fuels on a diesel engine was investigated.

abstract: Desert organisms lead harsh lives owing to the extreme, often unpredictable environmental conditions they endure. Climate change will likely make their existence even harsher. Predicting the ecological consequences of future climate scenarios thus requires understanding how the biota will be affected by climatic shifts. Biological soil crusts (biocrusts) are an important ecosystem component in arid lands, one that covers large portions of the landscape, improving soil stability and fertility. Because cyanobacteria are biocrust’s preeminent primary producers, eking out an existence during short pulses of precipitation, they represent a relevant global change object of study. I assessed how climate scenarios predicted for the Southwestern United States (US) will affect biocrusts using long-term, rainfall-modifying experimental set-ups that imposed either more intense drought, a seasonally delayed monsoon season, or a shift to smaller but more frequent precipitation events. I expected drought to be detrimental, but not a delay in the monsoon season. Surprisingly, both treatments showed similar effects on cyanobacterial community composition and population size after four years. While successionally incipient biocrusts were unaffected, mature biocrusts lost biomass and diversity with treatment, especially among nitrogen-fixing cyanobacteria. In separate experiments, I assessed the effect of rainfall with modified event size and frequency after a decade of treatment. Small, frequent rainfall events surprisingly enhanced the diversity and biomass of bacteria and cyanobacteria, with clear winners and losers: nitrogen-fixing Scytonema sp. benefited, while Microcoleus vaginatus lost its dominance. As an additional finding, I could also show that water addition is not always beneficial to biocrusts, calling into question the notion that these are strictly water-limited systems. Finally, results interpretation was severely hampered by a lack of appropriate systematic treatment for an important group of biocrust cyanobacteria, the “Microcoleus steenstrupii complex”. I characterized the complex using a polyphasic approach, leading to the formal description of a new family (Porphyrosiphonaceae) of desiccation resistant cyanobacteria that includes 11 genera, of which 5 had to be newly described. Under the new framework, the distribution and abundance of biocrust cyanobacteria with respect to environmental conditions can now be understood. This body of work contributes significantly to explain current distributional patterns of biocrust cyanobacteria and to predict their fate in the face of climate change.
Dissertation/Thesis
Doctoral Dissertation Microbiology 2020

abstract: Biological soil crusts (biocrusts) are topsoil communities of organisms that contribute to soil fertility and erosion resistance in drylands. Anthropogenic disturbances can quickly damage these communities and their natural recovery can take decades. With the development of accelerated restoration strategies in mind, I studied physiological mechanisms controlling the establishment of cyanobacteria in biocrusts, since these photoautotrophs are not just the biocrust pioneer organisms, but also largely responsible for improving key soil attributes such as physical stability, nutrient content, water retention and albedo. I started by determining the cyanobacterial community composition of a variety of biocrust types from deserts in the Southwestern US. I then isolated a large number of cyanobacterial strains from these locations, pedigreed them based on their 16SrRNA gene sequences, and selective representatives that matched the most abundant cyanobacterial field populations. I then developed methodologies for large-scale growth of the selected isolates to produce location-specific and genetically autochthonous inoculum for restoration. I also developed and tested viable methodologies to physiologically harden this inoculum and improve its survival under harsh field conditions. My tests proved that in most cases good viability of the inoculum could be attained under field-like conditions. In parallel, I used molecular ecology approaches to show that the biocrust pioneer, Microcoleus vaginatus, shapes its surrounding heterotrophic microbiome, enriching for a compositionally-differentiated “cyanosphere” that concentrates the nitrogen-fixing function. I proposed that a mutualism based on carbon for nitrogen exchange between M. vaginatus and its cyanosphere creates a consortium that constitutes the true pioneer community enabling the colonization of nitrogen-poor, bare soils. Using the right mixture of photosynthetic and diazotrophic cultures will thus likely help in soil restoration. Additionally, using physiological assays and molecular meta-analyses, I demonstrated that the largest contributors to N2-fixation in late successional biocrusts (three genera of heterocystous cyanobacteria) partition their niche along temperature gradients, and that this can explain their geographic patterns of dominance within biocrusts worldwide. This finding can improve restoration strategies by incorporating climate-matched physiological types in inoculum formulations. In all, this dissertation resulted in the establishment of a comprehensive "cyanobacterial biocrust nursery", that includes a culture collection containing 101 strains, isolation and cultivation methods, inoculum design strategies as well as field conditioning protocols. It constitutes a new interdisciplinary application of microbiology in restoration ecology.
Dissertation/Thesis
Doctoral Dissertation Liberal Studies 2019

abstract: Biological soil crusts (biocrust) are photosynthetic communities of organisms forming in the top millimeters of unvegetated soil. Because soil crusts contribute several ecosystem services to the areas they inhabit, their loss under anthropogenic pressure has negative ecological consequences. There is a considerable interest in developing technologies for biocrust restoration such as biocrust nurseries to grow viable inoculum and the optimization of techniques for field deployment of this inoculum. For the latter, knowledge of the natural rates of biocrust dispersal is needed. Lateral dispersal can be based on self-propelled motility by component microbes, or on passive transport through propagule entrainment in runoff water or wind currents, all of which remain to be assessed. I focused my research on determining the capacity of biocrust for lateral self-propelled dispersal. Over the course of one year, I set up two greenhouse experiments where sterile soil substrates were inoculated with biocrusts and where the lateral advancement of biocrust and their cyanobacteria was monitored using time-course photography, discrete determination of soil chlorophyll a concentration, and microscopic observations. Appropriate uninoculated controls were also set up and monitored. These experiments confirm that cyanobacterial biological soil crusts are capable of laterally expanding when provided with presumably optimal watering regime similar to field conditions and moderate temperatures. The maximum temperatures of Sonoran Desert summer (up to 42 °C), exacerbated in the greenhouse setting (48 °C), caused a loss of biomass and the cessation of lateral dispersal, which resumed as temperature decreased. In 8 independent experiments, biocrust communities advanced laterally at an average rate of 2 cm per month, which is half the maximal rate possible based on the instantaneous speed of gliding motility of the cyanobacterium Microcoleus vaginatus. In a span of three months, populations of M. vaginatus, M. steenstrupii, and Scytonema spp. advanced 1 cm/month on average. The advancing crust front was found to be preferentially composed of hormogonia (differentiated, fast-gliding propagules of cyanobacteria). Having established the potential for laterally self-propelled community dispersal (without wind or runoff contributions) will help inform restoration efforts by proposing minimal inoculum size and optimal distance between inoculum patches.
Dissertation/Thesis
Masters Thesis Biology 2017

In arid and semi-arid deserts, soils are commonly covered with biological soil crusts. The study of arid biocrusts and their ecological function has become increasingly common in the literature over the last several decades. Interestingly, no mention is made of biological soil crusts in forested ecosystems, raising the question as to whether they exist in these areas and if they do, why they have yet to be recognized as such? Through the use a parallel logic, this study finds that biocrusts do indeed exist in forests, a novel relationship in forest ecology and seeks to determine if there exist ecophysical explanations for the abundance and distribution throughout the forest landscape. This study examined the effects of climate variables and substrate types on the abundance, distribution and overall cover of forest soil biocrust at fifty-two sites in southern Oregon, U.S.A. Sites were randomly selected within established buffer zones in the Siuslaw, Rogue-Sisikyou, Umpqua, and Fremont-Winema National Forests. The methods of Belnap et al 2001 were tested and then modified for application in forested ecosystems. Data were collected on the relative abundance and distribution of biocrust morphological groups across available substrates, community biocrust morphology, aspect, elevation and soil texture, pH and organic matter content. Site-specific data on average annual precipitation and minimum/maximum temperatures was collected using the PRISM Climate Model. This study found substrate colonization by specific morphological groups mixed across the study; though dominant communities were observed for each substrate present, substrate availability appears to be confounded by a number of variables (climate, stand age and structure and litter layer) not controlled for in this study. Biocrust community morphologies varied across sites, primarily influenced by the surface texture of the substrate and morphology of the individual. Relatively smooth surfaces (rock, bare soil) often resulted in smooth biocrust morphologies, whereas rough surfaces (dead wood, bare soil) tended to result in a rolling morphology. Litter layer directly influenced the relative proportion of substrates colonized, notably affecting dead wood and mineral soil biocrusts. Total biocrust cover increased as precipitation increased as did biocrust preference for dead wood substrates while mineral soil remained unchanged and rock surfaces were negatively represented. Aspect generally followed the anticipated distribution of total biocrust cover with the highest cover on N and NW aspects and lowest on the W aspect. Increases in elevation were negatively related to overall biocrust cover. Soil texture was not found to be directly related to overall biocrust cover, attributed in part to the highly adaptive nature of the biocrust community. Soil organic matter (SOM) influenced total biocrust cover with positive correlations between total cover and increasing SOM content. Soil pH increased as expected across the precipitation range (17 to 159 in/yr) of the transect. Total biocrust cover was found to trend with soil pH, but is believed to be attributed to the parallel relationship between precipitation and pH, rather than pH alone given the relative moderate pH range (4.39 to 6.54) of the study. The distribution and abundance of forest soil biocrusts is strongly influenced by precipitation. The confounding influence of precipitation to litter layer depth and organic matter content (through gradients of vegetative productivity) and soil pH further are concluded to influence substrate preference by morphological groups. Across the variables examined, similarities between the two communities (arid and forest) in response to climate and soil chemistry show parallel relations, justifying the formal establishment of biological soil crust community in forested regions. The differences between communities related to the presence of trees validate the establishment of forest soil biocrusts as distinct community in both form and ecological function with the forests.
Graduation date: 2013

Research Doctorate - Doctor of Philosophy (PhD)
The utilisation of biomass has drawn widespread attention due to the fast depletion of fossil energy resources and environmental challenges. Biocrude oil, derived from pyrolysis or liquefaction of lignocellulosic biomass, contains a high level of oxygen leading to some detrimental properties (high viscosity, high corrosivity, low heating value and low thermal stability). Therefore, hydrodeoxygenation of the biocrude is necessary to remove the oxygen atoms and produce value-added fuels and chemicals. Hydrodeoxygenation (HDO) is a two-step process which involves the hydrogenation and deoxygenation. The hydrogenation commonly occurs in the presence of metal sites, and the acid sites play a crucial role in the deoxygenation. Therefore, the HDO catalysts are routinely composed of metals (such as Pt, Pd, Ru, and Ni) and supports (ZrO₂, Al₂O₃ and zeolites). Due to the complexity of biocrude oil, a model compound (guaiacol), which possesses two different oxygen-containing groups, was employed in this study. In the first step, the Ru/BEA and Ru/ZSM-5 with varied Si/Al ratios were studied to examine the influence of supports with varying acidity and pore size on HDO of biocrude oil and guaiacol in a batch-type reactor operated at 4.0 MPa hydrogen. It was observed that a decrease in the Si/Al ratio of the support generated an increase in the yield of cyclohexane and a decrease in the yield of 2-methoxycyclohexanol in HDO of guaiacol. Both Ru/BEA and Ru/ZSM-5, possessing low Si/Al ratios, displayed a high activity for HDO for guaiacol while only Ru/BEA catalyst exhibits a high activity for HDO of biocrude oil. Catalyst characterisation shows that the Ru/BEA catalyst, with a low Si/Al ratio, not only possesses strong B acid sites but also contains extensive mesoporosity. Notably, these mesopores appear to facilitate the hydrogenation, deoxygenation, and ring-opening of large oxygenated and condensed-ring hydrocarbons in biocrude oil which then leads to a high yield of cycloalkanes. As expected, the Ru/Al₂O₃ and Ru/SiO₂ catalysts exhibit a high hydrogenation activity but a low deoxygenation activity in the HDO of guaiacol and biocrude oil due to the absence of B acid sites. These results suggest that the larger pore support, with strong B acid sites, engendered the observed HDO activity. The reaction pathway for the main components of biocrude oil was proposed based on the observed reaction product distribution. Although Ru-based catalysts display a high HDO activity, the high cost could hinder their wide application in industry. Therefore, metallic Ni, which is low cost, non-sulfided, and has the advantage of high hydrogenation activity was employed as the main metal phase in this project. The influence of catalyst pore size and shape selectivity on the catalytic hydrodeoxygenation (HDO) of biocrude oil has been investigated by comparing the activity of nickel catalysts on the supports of different pore sizes towards model compounds of increasing dimension. Five model compounds (guaiacol, anisole, phenanthrene, pyrene, and 1,3,5-trimethoxybenzene), and five zeolite supports (small-pore ZSM-5, medium-pore MOR, large-pore Beta and Y, and mesoporous Al-MCM-41) have been investigated. Hydrodeoxygenation and hydrogenation activities were determined on the basis of the yield of the associated cycloalkanes. All catalysts show a high HDO activity for small molecules (anisole and guaiacol) while the catalysts with medium and large pore supports display high HDO activity for 1,3,5-trimethoxybenzene. Furthermore, the large pore catalysts (Ni/Y and Ni/Beta) exhibit high hydrogenation activity for phenanthrene, while only the extra-large pore size catalyst (Ni/Y) presents good hydrogenation and HDO activities for all model compounds. The mesoporous Ni/Al-MCM-41 catalyst shows low HDO and hydrogenation activities for large model compounds, which can be ascribed to its low metal dispersion and low concentration of acid sites. In addition, the Ni/Beta and Ni/ZSM-5 were also tested in HDO of biocrude oil. Ni/Beta catalyst displays a higher yield of cycloalkanes than that of Ni/ZSM-5, which confirms that the selection of catalyst support can have impact on the product distribution in HDO of biocrude. The BEA supported Ni catalyst, which possesses high concentration of acid sites and mesopores, displays a high HDO activity for guaiacol and biocrude oil, however, results from batch reactor cannot provide the information about turnover frequency of active sites. Therefore BEA zeolite, with different Si/Al ratios (12.5, 25, 175) and varying metal loadings (2.3 ~23.4 wt%), was studied in a flow reactor to examine the influence of catalyst acidity and the structure of Ni on the performance, with particular emphasis on the change in product selectivity. The ratio of cyclohexane formation rate to the concentration of acid sites in reduced catalysts was found to be roughly constant when HDO of guaiacol in a flow reactor over 15.7 wt% Ni/BEA catalysts with different acid site concentrations, demonstrating the deoxygenation activity increases with increasing number of acid sites. On the other hand, the materials with the majority of isolated Ni sites (prepared by ion exchange) showed no cyclohexane yield at 230 degree. However, at higher temperatures, the formation of cyclohexane was observed, as a result of a consecutive reaction where catechol was generated by acid sites and subsequently reduced to cyclohexane on isolated Ni sites. With respect to catalysts with higher Ni-loading, the selectivity towards cyclohexane increases with an increased Ni loading up to 15.7 wt%. This is attributed to the formation of larger Ni nanoparticles upon H₂ reduction. A higher concentration of nickel hydrides compared to isolated Ni sites was observed by H₂-TPD and H₂-FTIR. The nickel hydrides are believed to be crucial intermediates in the hydrogenation reaction. Based on the product distribution over catalysts containing mainly isolated Ni sites and the Ni nanoparticles, two different reaction pathways were proposed. Traditionally, catalysts with high metal loadings are indispensable for improved catalytic performance. Supported metal catalysts are typically prepared by incipient wetness impregnation, which inevitably gives rise to inhomogeneous metal distribution and leads to large metal particles formed via agglomeration. Therefore, highly dispersed Ni/BEA catalysts prepared via ion-exchange-deposition-precipitation (IDP) utilising careful pH control were conducted. In comparison, catalysts prepared by incipient wetness impregnation (IWI) and deposition-precipitation (DP) methods were also investigated and IDP catalysts were shown to have higher dispersion. A significantly increased selectivity toward hydrocarbons was observed over these carefully prepared catalysts. The presence of nickel hydrides was confirmed by H₂-TPD and H₂-FTIR. IDP catalyst exhibits a higher metal dispersion and higher concentration of nickel hydrides than impregnated and DP catalysts, while larger Ni nanoparticles formed in impregnated catalysts show a higher concentration of nickel hydrides per surface Ni. The guaiacol conversion was not significantly affected by the catalyst preparation method, while the product selectivity was altered. Higher cyclohexane formation rate was detected over IDP catalysts compared to DP and impregnated catalysts. Besides, cyclohexane formation rate presents a positive linear correlation with the concentration of nickel hydrides, suggesting nickel hydrides play a crucial role in the hydrodeoxygenation reaction. The factors affecting catalyst deactivation during HDO in a continuous-flow reactor were investigated in order to gain insight into the deactivation mechanism of BEA-supported Ni catalyst. Phenolic-OH group moieties accelerate catalyst deactivation through the production of condensed-ring compounds, which then leads to the blockage of pores. In contrast, the yield of cycloalkane did not change with time-on-stream when using toluene, cyclohexanol and anisole as feeds, suggesting aromatic-ring, alkyl-OH and aromatic-OCH₃ have negligible effect on catalyst deactivation. Operation at low weight hour space velocity (WHSV) values increase the yield of cycloalkane and reduce the rate of catalyst deactivation. High metal loadings can increase selectivity to cyclohexane, however, the production of condensed-ring products is also enhanced, which is likely to be the result of an increased concentration of surface cyclohexane carbocations. Furthermore, high metal loadings play a limited role in preventing the catalyst from deactivation. In addition, the activity and stability of catalysts were positively affected by an increase in reaction temperature (up to 230°C). Based on the product distribution observed, a coupling reaction pathway (leading to the formation of condensed-ring products and cycloalkanes) is proposed.