Oxidation and pyrolysis of methane and methyl formate in a plug flow reactor: computational and experimenal studies

Biodiesel represents a possible substitute to the fossil fuels; for this reason a good comprehension of the kinetics involved is important. Due to the complexity of the biodiesel mixture a common practice is the use of surrogate molecules to study its reactivity. In this work are presented the experimental and computational results obtained for the oxidation and pyrolysis of methane and methyl formate conducted in a plug flow reactor. The work was divided into two parts: the first one was the setup assembly whilst, in the second one, was realized a comparison between the experimental and model results; these last was obtained using models available in literature. It was started studying the methane since, a validate model was available, in this way was possible to verify the reliability of the experimental results. After this first study the attention was focused on the methyl formate investigation. All the analysis were conducted at different temperatures, pressures and, for the oxidation, at different equivalence ratios. The results shown that, a good comprehension of the kinetics is reach but efforts are necessary to better evaluate kinetics parameters such as activation energy. The results even point out that the realized setup is adapt to study the oxidation and pyrolysis and, for this reason, it will be employed to study a longer chain esters with the aim to better understand the kinetic of the molecules that are part of the biodiesel mixture.

Experimental and computational study of methane and methyl formate pyrolysis and oxidation in a flow reactor

A study of the pyrolysis and oxidation (phi 0.5-1-2) of methane and methyl formate (phi 0.5) in a laboratory flow reactor (Length = 50 cm, inner diameter = 2.5 cm) has been carried out at 1-4 atm and 300-1300 K temperature range. Exhaust gaseous species analysis was realized using a gas chromatographic system, Varian CP-4900 PRO Mirco-GC, with a TCD detector and using helium as carrier for a Molecular Sieve 5Å column and nitrogen for a COX column, whose temperatures and pressures were respectively of 65°C and 150kPa. Model simulations using NTUA [1], Fisher et al. [12], Grana [13] and Dooley [14] kinetic mechanisms have been performed with CHEMKIN. The work provides a basis for further development and optimization of existing detailed chemical kinetic schemes.

Power Transient Analysis of Experimental Devices for Jules Horowitz Material Testing Reactor (JHR)

The objective of this thesis is the power transient analysis concerning experimental devices placed within the reflector of Jules Horowitz Reactor (JHR). Since JHR material testing facility is designed to achieve 100 MW core thermal power, a large reflector hosts fissile material samples that are irradiated up to total relevant power of 3 MW. MADISON devices are expected to attain 130 kW, conversely ADELINE nominal power is of some 60 kW. In addition, MOLFI test samples are envisaged to reach 360 kW for what concerns LEU configuration and up to 650 kW according to HEU frame. Safety issues concern shutdown transients and need particular verifications about thermal power decreasing of these fissile samples with respect to core kinetics, as far as single device reactivity determination is concerned. Calculation model is conceived and applied in order to properly account for different nuclear heating processes and relative time-dependent features of device transients. An innovative methodology is carried out since flux shape modification during control rod insertions is investigated regarding the impact on device power through core-reflector coupling coefficients. In fact, previous methods considering only nominal core-reflector parameters are then improved. Moreover, delayed emissions effect is evaluated about spatial impact on devices of a diffuse in-core delayed neutron source. Delayed gammas transport related to fission products concentration is taken into account through evolution calculations of different fuel compositions in equilibrium cycle. Provided accurate device reactivity control, power transients are then computed for every sample according to envisaged shutdown procedures. Results obtained in this study are aimed at design feedback and reactor management optimization by JHR project team. Moreover, Safety Report is intended to utilize present analysis for improved device characterization.

Investigation of a superthermal ultracold neutron source based on a solid deuterium converter for the TRIGA Mainz reactor

Research in fundamental physics with the free neutron is one of the key tools for testing the Standard Model at low energies. Most prominent goals in this field are the search for a neutron electric dipole moment (EDM) and the measurement of the neutron lifetime. Significant improvements of the experimental performance using ultracold neutrons (UCN) require reduction of both systematic and statistical errors.rnThe development and construction of new UCN sources based on the superthermal concept is therefore an important step for the success of future fundamental physics with ultracold neutrons. rnSignificant enhancement of today available UCN densities strongly correlates with an efficient use of an UCN converter material. The UCN converter here is to be understood as a medium which reduces the velocity of cold neutrons (CN, velocity of about 600 m/s) to the velocity of UCN (velocity of about 6 m/s).rnSeveral big research centers around the world are presently planning or constructing new superthermal UCN sources, which are mainly based on the use of either solid deuterium or superfluid helium as UCN converter.rnThanks to the idea of Yu.Pokotilovsky, there exists the opportunity to build competitive UCN sources also at small research reactors of the TRIGA type. Of course these smaller facilities don't promise high UCN densities of several 1000 UCN/cm³, but they are able to provide densities around 100 UCN/cm³ for experiments.rnIn the context of this thesis, it was possible to demonstrate succesfully the feasibility of a superthermal UCN source at the tangential beamport C of the research reactor TRIGA Mainz. Based on a prototype for the future UCN source at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRMII) in munich, which was planned and built in collaboration with the Technical University of Munich, further investigations and improvements were done and are presented in this thesis. rnIn parallel, a second UCN source for the radial beamport D was designed and built. The comissioning of this new source is foreseen in spring 2010.rnAt beamport D with its higher thermal neutron flux, it should be possible to increase the available UCN densities of 4 UCN/cm³ by minimum one order of magnitude.

Biofilm formation by the anaerobic pathogen Clostridium difficile

Clostridium difficile is an obligate anaerobic, Gram-positive, endospore-forming bacterium. Although an opportunistic pathogen, it is one of the important causes of healthcare-associated infections. While toxins TcdA and TcdB are the main virulence factors of C. difficile, the factors or processes involved in gut colonization during infection remain unclear. The biofilm-forming ability of bacterial pathogens has been associated with increased antibiotic resistance and chronic recurrent infections. Little is known about biofilm formation by anaerobic gut species. Biofilm formation by C. difficile could play a role in virulence and persistence of C. difficile, as seen for other intestinal pathogens. We demonstrate that C. difficile clinical strains, 630, and the strain isolated in the outbreak, R20291, form structured biofilms in vitro. Biofilm matrix is made of proteins, DNA and polysaccharide. Strain R20291 accumulates substantially more biofilm. Employing isogenic mutants, we show that virulence-associated proteins, Cwp84, flagella and a putative quorum sensing regulator, LuxS, Spo0A, are required for maximal biofilm formation by C. difficile. Moreover we demonstrate that bacteria in C. difficile biofilms are more resistant to high concentrations of vancomycin, a drug commonly used for treatment of CDI, and that inhibitory and sub-inhibitory concentrations of the same antibiotic induce biofilm formation. Surprisingly, clinical C. difficile strains from the same out-break, but from different origin, show differences in biofilm formation. Genome sequence analysis of these strains showed presence of a single nucleoide polymorphism (SNP) in the anti-σ factor RsbW, which regulates the stress-induced alternative sigma factor B (σB). We further demonstrate that RsbW, a negative regulator of alternative sigma factor B, has a role in biofilm formation and sporulation of C. difficile. Our data suggest that biofilm formation by C. difficile is a complex multifactorial process and may be a crucial mechanism for clostridial persistence in the host.

Methane production through anaerobic digestion of dedicated energy crops

Methane yield of ligno-cellulosic substrates (i.e. dedicated energy crops and agricultural residues) may be limited by their composition and structural features. Hence, biomass pre-treatments are envisaged to overcome this constraint. This thesis aimed at: i) assessing biomass and methane yield of dedicated energy crops; ii) evaluating the effects of hydrothermal pre-treatments on methane yield of Arundo; iii) investigating the effects of NaOH pre-treatments and iv) acid pre-treatments on chemical composition, physical structure and methane yield of two dedicated energy crops and one agricultural residue. Three multi-annual species (Arundo, Switchgrass and Sorghum Silk), three sorghum hybrids (Trudan Headless, B133 and S506) and a maize, as reference for AD, were studied in the frame of point i). Results exhibit the remarkable variation in biomass yield, chemical characteristics and potential methane yield. The six species alternative to maize deserve attention in view of a low need of external inputs but necessitate improvements in biodegradability. In the frame of point ii), Arundo was subjected to hydrothermal pre-treatments at different temperature, time and acid catalyst (with and without H2SO4). Pre-treatments determined a variable effect on methane yield: pre-treatments without acid catalyst achieved up to +23% CH4 output, while pre-treatments with H2SO4 catalyst incurred a methanogenic inhibition. Two biomass crops (Arundo and B133) and an agricultural residue (Barley straw) were subject to NaOH and acid pre-treatments, in the frame of point iii) and iv), respectively. Different pre-treatments determined a change of chemical and physical structure and an increase of methane yield: up to +30% and up to +62% CH4 output in Arundo with NaOH and acid pre-treatments, respectively. It is thereby demonstrated that pre-treatments can actually enhance biodegradability and subsequent CH4 output of ligno-cellulosic substrates, although pre-treatment viability needs to be evaluated at the level of full scale biogas plants in a perspective of profitable implementation.

Mikrobiologie der Fermentation in NawaRo-Biogasanlagen unter besonderer Berücksichtigung des Abbaus von Propionsäure

In NawaRo-Biogasanlagen (BGA) kann es durch das Angebot an leicht fermentierbaren Kohlenstoff¬quel¬len zu einer bakteriell bedingten Übersäuerung durch unerwünschte kurzkettige Fettsäuren kommen. Häufiger kommt es zur Akkumulation von Propionsäure. Methanogene Archaea können bei niedrigen pH-Werten nicht mehr wachsen. Somit kann der gesamte Prozess der mikrobiellen Bildung von Biogas zum Erliegen kom¬men, was für die Biogasbetreiber zu erheblichen finanziellen Verlusten führt. Das Ziel dieser Disserta¬tion war die Aufklärung der anaeroben bakteriellen Population, die in Biogasanlagen Propionsäure ab¬bauen kann. Aus Propionat entsteht dabei Acetat und Wasserstoff. Da dieser anaerobe Prozess endergon verläuft, kann Propionsäure anaerob nur abgebaut werden, wenn der Wasserstoffpartialdruck niedrig ge¬halten wird. Diese Aufgabe erfüllen in Biogasanalgen methanogene Archaea. Die sog. sekundären Gärer leben somit in synthropher Kultur mit methanogenen Archaea.rnIn dieser Arbeit wurden die Mikroorganismen von Propionsäure-abbauenden Anreicherungskulturen aus vier NawaRo-BGA‘s identifiziert und ihr Substrat- und Produktspektrum analysiert. Die Anreicherungskul¬turen wurden vom Prüf- und Forschungsinstitut e. V. in Pirmasens zur Verfügung gestellt. Durch Analyse der bakteriellen 16S rDNA-Sequenzen der erhaltenen stabilen Propionsäure-abbauenden Mischkulturen wurde gezeigt, dass sich unter den Bakterien hauptsächlich Verwandte von den Clostridiales, aber auch Bacteroides sp., δ-, ε- so¬wie γ-Proteobakterien, Spirochäten, Synergistales und ungewöhnlicher Weise auch Thermotogales befanden. Aus Propionsäure-abbauenden Mischkulturen und aus Fermentern mesophiler NawaRo-Biogasanlagen wurden anaerobe Bakterien und methanogene Archaea angereichert und isoliert. Es wurden aus den Propionsäure-abbauenden Mischkulturen Stämme in Reinkultur erhalten, die entsprechend der 16S rDNA-Analyse als Clostridium sartagoforme Stamm Ap1a520 und Proteiniphilum acetatigenes Stamm Fp1a520 identifiziert wurden. Sowohl aus Fermentern und Nachgärern von drei NawaRo-BGA‘s als auch aus zwei Laborfermentern des Leibniz-Instituts für Agrartechnik in Potsdam-Bornim e.V. (ATB) wurden Reinkulturen von methanogenen Archaea erhalten. Diese konnten den Species Methanobacterium formicicum, Metha¬noculleus bourgensis, Methanosarcina barkeri, Methanosarcina mazei, Methanosarcina sp., Methanosaeta concilii und Methanomethylovorans sp. zugeordnet werden. Damit wurden in dieser Arbeit unter anderem die typischen bisher nur durch molekularbiologische Methoden identifizierten Species methanogener Ar¬chaea aus unterschiedlichen Fermentern in Reinkultur erhalten. Dabei wurde gezeigt, dass die specifically amplified polymorphic DNA-PCR (SAPD-PCR) eine geeignete Methode darstellt, Stämme der gleichen Art methanogener Archaea voneinander zu unterscheiden. Die Methanproduktion der kultivierten methanoge¬nen Archaea wurde gaschromatographisch analysiert. Es zeigte sich, dass die hydrogenotrophe Metha¬nogenese der effizientere und ergiebigere Weg zur Bildung von Methan ist. Mit der Bestimmung der Zellzahl des Isolates Methanoculleus bourgensis Stamm TAF1.1 bei gleichzeitiger Messung der Methanbildung wurde gezeigt, dass die Methanbildung nicht zwangsläufig mit dem Wachstum korreliert. Ne-ben Pflanzenfasern beinhalteten das hergestellte Reaktorfiltrat in den Kultivierungsansätzen Acetat, die essentielle Aminosäure Valin und den Zuckeralkohol Glycerol. Gezielte Misch¬kul¬turen von sekundären Gärern mit methanogenen Isolaten ergaben einen fördernden Einfluss auf diese Bak¬terien durch hydrogenotrophe Archaea. Diese Bakterien bauten Substrate ab oder bildeten Produkte, die sie unter den gegebenen Bedingungen ohne hydrogenotrophe Archaea nicht umsetzen konnten.

Development and application of a thermo-hydraulic model supporting the design and the deterministic safety analysis in a sodium cooled fast reactor

Il CP-ESFR è un progetto integrato di cooperazione europeo sui reattori a sodio SFR realizzato sotto il programma quadro EURATOM 7, che unisce il contributo di venticinque partner europei. Il CP-ESFR ha l'ambizione di contribuire all'istituzione di una "solida base scientifica e tecnica per il reattore veloce refrigerato a sodio, al fine di accelerare gli sviluppi pratici per la gestione sicura dei rifiuti radioattivi a lunga vita, per migliorare le prestazioni di sicurezza, l'efficienza delle risorse e il costo-efficacia di energia nucleare al fine di garantire un sistema solido e socialmente accettabile di protezione della popolazione e dell'ambiente contro gli effetti delle radiazioni ionizzanti. " La presente tesi di laurea è un contributo allo sviluppo di modelli e metodi, basati sull’uso di codici termo-idraulici di sistema, per l’ analisi di sicurezza di reattori di IV Generazione refrigerati a metallo liquido. L'attività è stata svolta nell'ambito del progetto FP-7 PELGRIMM ed in sinergia con l’Accordo di Programma MSE-ENEA(PAR-2013). Il progetto FP7 PELGRIMM ha come obbiettivo lo sviluppo di combustibili contenenti attinidi minori 1. attraverso lo studio di due diverse forme: pellet (oggetto della presente tesi) e spherepac 2. valutandone l’impatto sul progetto del reattore CP-ESFR. La tesi propone lo sviluppo di un modello termoidraulico di sistema dei circuiti primario e intermedio del reattore con il codice RELAP5-3D© (INL, US). Tale codice, qualificato per il licenziamento dei reattori nucleari ad acqua, è stato utilizzato per valutare come variano i parametri del core del reattore rilevanti per la sicurezza (es. temperatura di camicia e di centro combustibile, temperatura del fluido refrigerante, etc.), quando il combustibile venga impiegato per “bruciare” gli attinidi minori (isotopi radioattivi a lunga vita contenuti nelle scorie nucleari). Questo ha comportato, una fase di training sul codice, sui suoi modelli e sulle sue capacità. Successivamente, lo sviluppo della nodalizzazione dell’impianto CP-ESFR, la sua qualifica, e l’analisi dei risultati ottenuti al variare della configurazione del core, del bruciamento e del tipo di combustibile impiegato (i.e. diverso arricchimento di attinidi minori). Il testo è suddiviso in sei sezioni. La prima fornisce un’introduzione allo sviluppo tecnologico dei reattori veloci, evidenzia l’ambito in cui è stata svolta questa tesi e ne definisce obbiettivi e struttura. Nella seconda sezione, viene descritto l’impianto del CP-ESFR con attenzione alla configurazione del nocciolo e al sistema primario. La terza sezione introduce il codice di sistema termico-idraulico utilizzato per le analisi e il modello sviluppato per riprodurre l’impianto. Nella sezione quattro vengono descritti: i test e le verifiche effettuate per valutare le prestazioni del modello, la qualifica della nodalizzazione, i principali modelli e le correlazioni più rilevanti per la simulazione e le configurazioni del core considerate per l’analisi dei risultati. I risultati ottenuti relativamente ai parametri di sicurezza del nocciolo in condizioni di normale funzionamento e per un transitorio selezionato sono descritti nella quinta sezione. Infine, sono riportate le conclusioni dell’attività.

Nanoparticle preparation process using novel microjet reactor technology for enhancing dissolution rates of poorly water soluble drugs

In this study a novel method MicroJet reactor technology was developed to enable the custom preparation of nanoparticles. rnDanazol/HPMCP HP50 and Gliclazide/Eudragit S100 nanoparticles were used as model systems for the investigation of effects of process parameters and microjet reactor setup on the nanoparticle properties during the microjet reactor construction. rnFollowing the feasibility study of the microjet reactor system, three different nanoparticle formulations were prepared using fenofibrate as model drug. Fenofibrate nanoparticles stabilized with poloxamer 407 (FN), fenofibrate nanoparticles in hydroxypropyl methyl cellulose phthalate (HPMCP) matrix (FHN) and fenofibrate nanoparticles in HPMCP and chitosan matrix (FHCN) were prepared under controlled precipitation using MicroJet reactor technology. Particle sizes of all the nanoparticle formulations were adjusted to 200-250 nm. rnThe changes in the experimental parameters altered the system thermodynamics resulting in the production of nanoparticles between 20-1000 nm (PDI<0.2) with high drug loading efficiencies (96.5% in 20:1 polymer:drug ratio).rnDrug releases from all nanoparticle formulations were fast and complete after 15 minutes both in FaSSIF and FeSSIF medium whereas in mucodhesiveness tests, only FHCN formulation was found to be mucoadhesive. Results of the Caco-2 studies revealed that % dose absorbed values were significantly higher (p<0.01) for FHCN in both cases where FaSSIF and FeSSIF were used as transport buffer.rn

Mikrobielle Prozesskontrolle in Biogasanlagen durch Monitoring der Kohlenstoff-Isotopenverhältnisse im Gasbereich

Der zunehmende Anteil von Strom aus erneuerbaren Energiequellen erfordert ein dynamisches Konzept, um Spitzenlastzeiten und Versorgungslücken aus der Wind- und Solarenergie ausgleichen zu können. Biogasanlagen können aufgrund ihrer hohen energetischen Verfügbarkeit und der Speicherbarkeit von Biogas eine flexible Energiebereitstellung ermöglichen und darüber hinaus über ein „Power-to-Gas“-Verfahren bei einem kurzzeitigen Überschuss von Strom eine Überlastung des Stromnetzes verhindern. Ein nachfrageorientierter Betrieb von Biogasanlagen stellt jedoch hohe Anforderungen an die Mikrobiologie im Reaktor, die sich an die häufig wechselnden Prozessbedingungen wie der Raumbelastung im Reaktor anpassen muss. Eine Überwachung des Fermentationsprozesses in Echtzeit ist daher unabdingbar, um Störungen in den mikrobiellen Gärungswegen frühzeitig erkennen und adäquat entgegenwirken zu können. rnBisherige mikrobielle Populationsanalysen beschränken sich auf aufwendige, molekularbiologische Untersuchungen des Gärsubstrates, deren Ergebnisse dem Betreiber daher nur zeitversetzt zur Verfügung stehen. Im Rahmen dieser Arbeit wurde erstmalig ein Laser-Absorptionsspektrometer zur kontinuierlichen Messung der Kohlenstoff-Isotopenverhältnisse des Methans an einer Forschungsbiogasanlage erprobt. Dabei konnten, in Abhängigkeit der Raumbelastung und Prozessbedingungen variierende Isotopenverhältnisse gemessen werden. Anhand von Isolaten aus dem untersuchten Reaktor konnte zunächst gezeigt werden, dass für jeden Methanogenesepfad (hydrogeno-troph, aceto¬klastisch sowie methylotroph) eine charakteristische, natürliche Isotopensignatur im Biogas nachgewiesen werden kann, sodass eine Identifizierung der aktuell dominierenden methanogenen Reaktionen anhand der Isotopen-verhältnisse im Biogas möglich ist. rnDurch den Einsatz von 13C- und 2H-isotopen¬markierten Substraten in Rein- und Mischkulturen und Batchreaktoren, sowie HPLC- und GC-Unter¬suchungen der Stoffwechselprodukte konnten einige bislang unbekannte C-Flüsse in Bioreaktoren festgestellt werden, die sich wiederum auf die gemessenen Isotopenverhältnisse im Biogas auswirken können. So konnte die Entstehung von Methanol sowie dessen mikrobieller Abbauprodukte bis zur finalen CH4-Bildung anhand von fünf Isolaten erstmalig in einer landwirtschaftlichen Biogasanlage rekonstruiert und das Vorkommen methylotropher Methanogenesewege nachgewiesen werden. Mithilfe molekularbiologischer Methoden wurden darüber hinaus methanoxidierende Bakterien zahlreicher, unbekannter Arten im Reaktor detektiert, deren Vorkommen aufgrund des geringen O2-Gehaltes in Biogasanlagen bislang nicht erwartet wurde. rnDurch die Konstruktion eines synthetischen DNA-Stranges mit den Bindesequenzen für elf spezifische Primerpaare konnte eine neue Methode etabliert werden, anhand derer eine Vielzahl mikrobieller Zielorganismen durch die Verwendung eines einheitlichen Kopienstandards in einer real-time PCR quantifiziert werden können. Eine über 70 Tage durchgeführte, wöchentliche qPCR-Analyse von Fermenterproben zeigte, dass die Isotopenverhältnisse im Biogas signifikant von der Zusammensetzung der Reaktormikrobiota beeinflusst sind. Neben den aktuell dominierenden Methanogenesewegen war es auch möglich, einige bakterielle Reaktionen wie eine syntrophe Acetatoxidation, Acetogenese oder Sulfatreduktion anhand der δ13C (CH4)-Werte zu identifizieren, sodass das hohe Potential einer kontinuierlichen Isotopenmessung zur Prozessanalytik in Biogasanlagen aufgezeigt werden konnte.rn

Development of a biorefinery scheme for the valorization of olive mill wastewaters and grape pomaces

In the Mediterranean area, olive mill wastewater (OMW) and grape pomace (GP) are among the major agro-industrial wastes produced. These two wastes have a high organic load and high phytotoxicity. Thus, their disposal in the environment can lead to negative effects. Second-generation biorefineries are dedicated to the valorization of biowaste by the production of goods from such residual biomasses. This approach can combine bioremediation approaches to the generation of noble molecules, biomaterials and energy. The main aim of this thesis work was to study the anaerobic digestion of OMW and GP under different operational conditions to produce volatile fatti acids (VFAs) (first stage aim) and CH4 (second stage aim). To this end, a packed-bed biofilm reactor (PBBR) was set up to perform the anaerobic acidogenic digestion of the liquid dephenolized stream of OMW (OMWdeph). In parallel, the solid stream of OMW (OMWsolid), previously separated in order to allow the solid phase extraction of polyphenols, was addressed to anaerobic methanogenic digestion to obtain CH4. The latter experiment was performed in 100ml Pyrex bottles which were maintained at different temperatures (55-45-37°C). Together with previous experiments, the anaerobic acidogenic digestion of fermented GP (GPfreshacid) and dephenolized and fermented GP (GPdephacid) was performed in 100ml Pyrex bottles to estimate the concentration of VFAs achievable from each aforementioned GPs. Finally, the same matrices of GP and not pre-treated GP (GPfresh) were digested under anaerobic methanogenic condition to produce CH4. Anaerobic acidogenic and methanogenic digestion processes of GPs lasted about 33 days. Instead, the anaerobic acidogenic and methanogenic digestion process of OMWs lasted about 121 and 60 days, respectively. Each experiment was periodically monitored by analysing volume and composition of produced biogas and VFA concentration. Results showed that VFAs were produced in higher concentrations in GP compared to OMWdeph. The overall concentration of VFAs from GPfreshacid was approximately 39.5 gCOD L-1, 29 gCOD L-1 from GPdephacid, and 8.7 gCOD L-1 from OMWdeph. Concerning the CH4 production, the OMWsolid reached a high biochemical methane potential (BMP) at a thermophilic temperature (55°) than at mesophlic ones (37-45°C). The value reached was about 358.7 mlCH4 gSVsub-1. In contrast, GPfresh got a high BMP but at a mesophilic temperature. The BMP was about 207.3 mlCH4 gSVsub-1, followed by GPfreshacid with about 192.6 mlCH4 gSVsub-1 and lastly GPdephacid with about 102.2 mlCH4 gSVsub-1. In summary, based on the gathered results, GP seems to be a better carbon source for acidogenic and methanogenic microrganism compared to OMW, because higher amount of VFAs and CH4 were produced in AD of GP than OMW. In addition to these products, polyphenols were extracted by means of a solid phase extraction (SPE) procedure by another research group, and VFAs were utilised for biopolymers production, in particular polyhydroxyalkanoates (PHAs), by the same research group in which I was involved.

Biogas and bio-hydrogen: production and uses. A review

The first part of this essay aims at investigating the already available and promising technologies for the biogas and bio-hydrogen production from anaerobic digestion of different organic substrates. One strives to show all the peculiarities of this complicate process, such as continuity, number of stages, moisture, biomass preservation and rate of feeding. The main outcome of this part is the awareness of the huge amount of reactor configurations, each of which suitable for a few types of substrate and circumstance. Among the most remarkable results, one may consider first of all the wet continuous stirred tank reactors (CSTR), right to face the high waste production rate in urbanised and industrialised areas. Then, there is the up-flow anaerobic sludge blanket reactor (UASB), aimed at the biomass preservation in case of highly heterogeneous feedstock, which can also be treated in a wise co-digestion scheme. On the other hand, smaller and scattered rural realities can be served by either wet low-rate digesters for homogeneous agricultural by-products (e.g. fixed-dome) or the cheap dry batch reactors for lignocellulose waste and energy crops (e.g. hybrid batch-UASB). The biological and technical aspects raised during the first chapters are later supported with bibliographic research on the important and multifarious large-scale applications the products of the anaerobic digestion may have. After the upgrading techniques, particular care was devoted to their importance as biofuels, highlighting a further and more flexible solution consisting in the reforming to syngas. Then, one shows the electricity generation and the associated heat conversion, stressing on the high potential of fuel cells (FC) as electricity converters. Last but not least, both the use as vehicle fuel and the injection into the gas pipes are considered as promising applications. The consideration of the still important issues of the bio-hydrogen management (e.g. storage and delivery) may lead to the conclusion that it would be far more challenging to implement than bio-methane, which can potentially “inherit” the assets of the similar fossil natural gas. Thanks to the gathered knowledge, one devotes a chapter to the energetic and financial study of a hybrid power system supplied by biogas and made of different pieces of equipment (natural gas thermocatalitic unit, molten carbonate fuel cell and combined-cycle gas turbine structure). A parallel analysis on a bio-methane-fed CCGT system is carried out in order to compare the two solutions. Both studies show that the apparent inconvenience of the hybrid system actually emphasises the importance of extending the computations to a broader reality, i.e. the upstream processes for the biofuel production and the environmental/social drawbacks due to fossil-derived emissions. Thanks to this “boundary widening”, one can realise the hidden benefits of the hybrid over the CCGT system.

A New Reactor Concept for Efficient Solar-Thermochemical Fuel Production

We describe and analyze the efficiency of a new solar-thermochemical reactor concept, which employs a moving packed bed of reactive particles produce of H2 or CO from solar energy and H2O or CO2. The packed bed reactor incorporates several features essential to achieving high efficiency: spatial separation of pressures, temperature, and reaction products in the reactor; solid–solid sensible heat recovery between reaction steps; continuous on-sun operation; and direct solar illumination of the working material. Our efficiency analysis includes material thermodynamics and a detailed accounting of energy losses, and demonstrates that vacuum pumping, made possible by the innovative pressure separation approach in our reactor, has a decisive efficiency advantage over inert gas sweeping. We show that in a fully developed system, using CeO2 as a reactive material, the conversion efficiency of solar energy into H2 and CO at the design point can exceed 30%. The reactor operational flexibility makes it suitable for a wide range of operating conditions, allowing for high efficiency on an annual average basis. The mixture of H2 and CO, known as synthesis gas, is not only usable as a fuel but is also a universal starting point for the production of synthetic fuels compatible with the existing energy infrastructure. This would make it possible to replace petroleum derivatives used in transportation in the U.S., by using less than 0.7% of the U.S. land area, a roughly two orders of magnitude improvement over mature biofuel approaches. In addition, the packed bed reactor design is flexible and can be adapted to new, better performing reactive materials.

A New Reactor Concept for Efficient Solar-Thermochemical Fuel Production

We describe and analyze the efficiency of a new solar-thermochemical reactor concept, which employs a moving packed bed of reactive particles produce of H-2 or CO from solar energy and H2O or CO2. The packed bed reactor incorporates several features essential to achieving high efficiency: spatial separation of pressures, temperature, and reaction products in the reactor; solid-solid sensible heat recovery between reaction steps; continuous on-sun operation; and direct solar illumination of the working material. Our efficiency analysis includes material thermodynamics and a detailed accounting of energy losses, and demonstrates that vacuum pumping, made possible by the innovative pressure separation approach in our reactor, has a decisive efficiency advantage over inert gas sweeping. We show that in a fully developed system, using CeO2 as a reactive material, the conversion efficiency of solar energy into H-2 and CO at the design point can exceed 30%. The reactor operational flexibility makes it suitable for a wide range of operating conditions, allowing for high efficiency on an annual average basis. The mixture of H-2 and CO, known as synthesis gas, is not only usable as a fuel but is also a universal starting point for the production of synthetic fuels compatible with the existing energy infrastructure. This would make it possible to replace petroleum derivatives used in transportation in the U. S., by using less than 0.7% of the U. S. land area, a roughly two orders of magnitude improvement over mature biofuel approaches. In addition, the packed bed reactor design is flexible and can be adapted to new, better performing reactive materials.