Influence of alternative electron acceptors on the anaerobic biodegradation of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons are chemicals produced by both human activities and natural sources and they have been present in the biosphere since millions of years. For this reason microorganisms should have developed, during the world history, the capacity of metabolized them under different electron acceptors and redox conditions. The deep understanding of these natural attenuation processes and of microbial degradation pathways has a main importance in the cleanup of contaminated areas. Anaerobic degradation of aromatic hydrocarbons is often presumed to be slow and of a minor ecological significance compared with the aerobic processes; however anaerobic bioremediation may play a key role in the transformation of organic pollutants when oxygen demand exceeds supply in natural environments. Under such conditions, anoxic and anaerobic degradation mediated by denitrifying or sulphate-reducing bacteria can become a key pathway for the contaminated lands clean up. Actually not much is known about anaerobic bioremediation processes. Anaerobic biodegrading techniques may be really interesting for the future, because they give the possibility of treating contaminated soil directly in their natural status, decreasing the costs concerning the oxygen supply, which usually are the highest ones, and about soil excavations and transports in appropriate sites for a further disposal. The aim of this dissertation work is to characterize the conditions favouring the anaerobic degradation of polycyclic aromatic hydrocarbons. Special focus will be given to the assessment of the various AEA efficiency, the characterization of degradation performance and rates under different redox conditions as well as toxicity monitoring. A comparison with aerobic and anaerobic degradation concerning the same contaminated material is also made to estimate the different biodegradation times.

Life Cycle Assessment comparativo tra il processo di co-digestione della frazione organica dei rifiuti solidi urbani e dei fanghi di depurazione disidratati e il sistema di gestione attuale. Il caso di Bagnacavallo (RA)

Waste management is becoming, year after year, always more important both for the costs associated with it and for the ever increasing volumes of waste generated. The discussion on the fate of organic fraction of municipal solid waste (OFMSW) leads everyday to new solutions. Many alternatives are proposed, ranging from incineration to composting passing through anaerobic digestion. “For Biogas” is a collaborative effort, between C.I.R.S.A. and R.E.S. cooperative, whose main goal is to generate “green” energy from both biowaste and sludge anaerobic co-digestion. Specifically, the project include a pilot plant receiving dewatered sludge from both urban and agro-industrial sewage (DS) and the organic fraction of MSW (in 2/1 ratio) which is digested in absence of oxygen to produce biogas and digestate. Biogas is piped to a co-generation system producing power and heat reused in the digestion process itself, making it independent from the national grid. Digestate undergoes a process of mechanical separation giving a liquid fraction, introduced in the treatment plant, and a solid fraction disposed in landfill (in future it will be further processed to obtain compost). This work analyzed and estimated the impacts generated by the pilot plant in its operative phase. Once the model was been characterized, on the basis of the CML2001 methodology, a comparison is made with the present scenario assumed for OFMSW and DS. Actual scenario treats separately the two fractions: the organic one is sent to a composting plant, while sludge is sent to landfill. Results show that the most significant difference between the two scenarios is in the GWP category as the project "For Biogas" is able to generate “zero emission” power and heat. It also generates a smaller volume of waste for disposal. In conclusion, the analysis evaluated the performance of two alternative methods of management of OFMSW and DS, highlighting that "For Biogas" project is to be preferred to the actual scenario.

Outdoor bronze conservation: assessment of protective treatments by accelerated aging and of treatment removal procedures by laser cleaning

Outdoor bronzes exposed to the environment form naturally a layer called patina, which may be able to protect the metallic substrate. However, since the last century, with the appearance of acid rains, a strong change in the nature and properties of the copper based patinas occurred [1]. Studies and general observations have established that bronze corrosion patinas created by acid rain are not only disfiguring in terms of loss of detail and homogeneity, but are also unstable [2]. The unstable patina is partially leached away by rainwater. This leaching is represented by green streaking on bronze monuments [3]. Because of the instability of the patina, conservation techniques are usually required. On a bronze object exposed to the outdoor environment, there are different actions of the rainfall and other atmospheric agents as a function of the monument shape. In fact, we recognize sheltered and unsheltered areas as regards exposure to rainwater [4]. As a consequence of these different actions, two main patina types are formed on monuments exposed to the outdoor environment. These patinas have different electrochemical, morphological and compositional characteristics [1]. In the case of sheltered areas, the patina contains mainly copper products, stratified above a layer strongly enriched in insoluble Sn oxides, located at the interface with the uncorroded metal. Moreover, different colors of the patina result from the exposure geometry. The surface color may be pale green for unsheltered areas, and green and mat black for sheltered areas [4]. Thus, in real outdoor bronze monuments, the corrosion behavior is strongly influenced by the exposure geometry. This must be taken into account when designing conservation procedures, since the patina is in most cases the support on which corrosion inhibitors are applied. Presently, for protecting outdoor bronzes against atmospheric corrosion, inhibitors and protective treatments are used. BTA and its derivatives, which are the most common inhibitors used for copper and its alloy, were found to be toxic for the environment and human health [5, 6]. Moreover, it has been demonstrated that BTA is efficient when applied on bare copper but not as efficient when applied on bare bronze [7]. Thus it was necessary to find alternative compounds. Silane-based inhibitors (already successfully tested on copper and other metallic substrates [8]), were taken into consideration as a non-toxic, environmentally friendly alternative to BTA derivatives for bronze protection. The purpose of this thesis was based on the assessment of the efficiency of a selected compound, to protect the bronze against corrosion, which is the 3-mercapto-propyl-trimethoxy-silane (PropS-SH). It was selected thanks to the collaboration with the Corrosion Studies Centre “Aldo Daccò” at the Università di Ferrara. Since previous studies [9, 10, 11] demonstrated that the addition of nanoparticles to silane-based inhibitors leads to an increase of the protective efficiency, we also wanted to evaluate the influence of the addition of CeO2, La2O3, TiO2 nanoparticles on the protective efficiency of 3-mercapto-propyl-trimethoxy-silane, applied on pre-patinated bronze surfaces. This study is the first section of the thesis. Since restorers have to work on patinated bronzes and not on bare metal (except for contemporary art), it is important to be able to recreate the patina, under laboratory conditions, either in sheltered or unsheltered conditions to test the coating and to obtain reliable results. Therefore, at the University of Bologna, different devices have been designed to simulate the real outdoor conditions and to create a patina which is representative of real application conditions of inhibitor or protective treatments. In particular, accelerated ageing devices by wet & dry (simulating the action of stagnant rain in sheltered areas [12]) and by dropping (simulating the leaching action of the rain in unsheltered areas [1]) tests were used. In the present work, we used the dropping test as a method to produce pre-patinated bronze surfaces for the application of a candidate inhibitor as well as for evaluating its protective efficiency on aged bronze (unsheltered areas). In this thesis, gilded bronzes were also studied. When they are exposed to the outside environment, a corrosion phenomenon appears which is due to the electrochemical couple gold/copper where copper is the anode. In the presence of an electrolyte, this phenomenon results in the formation of corrosion products than will cause a blistering of the gold (or a break-up and loss of the film in some cases). Moreover, because of the diffusion of the copper salts to the surface, aggregates and a greenish film will be formed on the surface of the sample [13]. By coating gilded samples with PropS-SH and PropS-SH containing nano-particles and carrying out accelerated ageing by the dropping test, a discussion is possible on the effectiveness of this coating, either with nano-particles or not, against the corrosion process. This part is the section 2 of this thesis. Finally, a discussion about laser treatment aiming at the assessment of reversibility/re-applicability of the PropS-SH coating can be found in section 3 of this thesis. Because the protective layer loses its efficiency with time, it is necessary to find a way of removing the silane layer, before applying a new one on the “bare” patina. One request is to minimize the damages that a laser treatment would create on the patina. Therefore, different laser fluences (energy/surface) were applied on the sample surface during the treatment process in order to find the best range of fluence. In particular, we made a characterization of surfaces before and after removal of PropS-SH (applied on a naturally patinated surface, and subsequently aged by natural exposure) with laser methods. The laser removal treatment was done by the CNR Institute of Applied Physics “Nello Carrara” of Sesto Fiorentino in Florence. In all the three sections of the thesis, a range of non-destructive spectroscopic methods (Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), μ-Raman spectroscopy, X-Ray diffractometry (XRD)) were used for characterizing the corroded surfaces. AAS (Atomic Absorption Spectroscopy) was used to analyze the ageing solutions from the dropping test in sections 1 and 2.

Analisi del ciclo di vita della produzione industriale di acroleina: confronto tra il processo tradizionale e vie di sintesi alternative.

La green chemistry può essere definita come l’applicazione dei principi fondamentali di sviluppo sostenibile, al fine di ridurre al minimo l’impiego o la formazione di sostanze pericolose nella progettazione, produzione e applicazione di prodotti chimici. È in questo contesto che si inserisce la metodologia LCA (Life Cycle Assessment), come strumento di analisi e di valutazione. Il presente lavoro di tesi è stato condotto con l’intenzione di offrire una valutazione degli impatti ambientali associati al settore dei processi chimici di interesse industriale in una prospettiva di ciclo di vita. In particolare, è stato studiato il processo di produzione di acroleina ponendo a confronto due vie di sintesi alternative: la via tradizionale che impiega propilene come materia prima, e l’alternativa da glicerolo ottenuto come sottoprodotto rinnovabile di processi industriali. Il lavoro si articola in due livelli di studio: un primo, parziale, in cui si va ad esaminare esclusivamente il processo di produzione di acroleina, non considerando gli stadi a monte per l’ottenimento delle materie prime di partenza; un secondo, più dettagliato, in cui i confini di sistema vengono ampliati all’intero ciclo produttivo. I risultati sono stati confrontati ed interpretati attraverso tre tipologie di analisi: Valutazione del danno, Analisi di contributo ed Analisi di incertezza. Dal confronto tra i due scenari parziali di produzione di acroleina, emerge come il processo da glicerolo abbia impatti globalmente maggiori rispetto al tradizionale. Tale andamento è ascrivibile ai diversi consumi energetici ed in massa del processo per l’ottenimento dell’acroleina. Successivamente, per avere una visione completa di ciascuno scenario, l’analisi è stata estesa includendo le fasi a monte di produzione delle due materie prime. Da tale confronto emerge come lo scenario più impattante risulta essere quello di produzione di acroleina partendo da glicerolo ottenuto dalla trans-esterificazione di olio di colza. Al contrario, lo scenario che impiega glicerolo prodotto come scarto della lavorazione di sego sembra essere il modello con i maggiori vantaggi ambientali. Con l’obiettivo di individuare le fasi di processo maggiormente incidenti sul carico totale e quindi sulle varie categorie d’impatto intermedie, è stata eseguita un’analisi di contributo suddividendo ciascuno scenario nei sotto-processi che lo compongono. È stata infine eseguita un’analisi di incertezza tramite il metodo Monte Carlo, verificando la riproducibilità dei risultati.

Life cycle assessment comparativa di processi di estrazione di poliidrossialcanoati da colture batteriche

I materiali plastici trovano ampie applicazioni in ogni aspetto della vita e delle attività industriali. La maggior parte delle plastiche convenzionali non sono biodegradabili e il loro accumulo è una minaccia per il pianeta. I biopolimeri presentano vantaggi quali: la riduzione del consumo delle risorse e la riduzione delle emissioni CO2, offrendo un importante contributo allo sviluppo sostenibile. Tra i biopolimeri più interessanti troviamo il poliidrossibutirrato (PHB), l’oggetto di questo studio, che è il più noto dei poliidrossialcanoati. Questo polimero biodegradabile mostra molte somiglianze con il polipropilene. La tesi consiste nell’applicazione del Life Cycle Assessment a processi di estrazione del PHB da colture batteriche. In essa sono valutate le prestazioni ambientali di 4 possibili processi alternativi, sviluppati dal CIRI EA, che utilizzano il dimetilcarbonato (DMC) e di 3 processi che utilizzano solventi alogenati (cloroformio, diclorometano, dicloroetano). Per quanto riguarda i processi che utilizzano come solvente di estrazione il DMC, due sono gli aspetti indagati e per i quali differiscono le alternative: la biomassa di partenza (secca o umida), e il metodo di separazione del polimero dal solvente (per evaporazione del DMC oppure per precipitazione). I dati primari di tutti gli scenari sono di laboratorio per cui è stato necessario realizzare un up scaling industriale di tutti i processi. L’up scaling è stato realizzato in collaborazione con il Dipartimento di Ingegneria Civile Chimica Ambientale e dei Materiali. La valutazione delle prestazioni ambientali è stata fatta rispetto a tutte le categorie d’impatto raccomandate dall’Handbook della Commissione Europea, di queste solo alcune sono state analizzate nel dettaglio. Tutti i risultati mostrano un andamento simile, in cui gli impatti dei processi che utilizzano DMC sono inferiori a quelli dei solventi alogenati. Fra i processi che impiegano DMC, l’alternativa più interessante appare quella che impiega biomassa di partenza secca e raccolta del PHB per precipitazione.

Risk assessment of liquid hydrogen tanks for heavy duty vehicles

The advent of the hydrogen economy has already been predicted but it does not represent a tangible reality yet. However, decarbonizing the global economy and particularly the energy sector is vital to limit global warming and reduce the incumbent environmental problems. Hydrogen is a promising zero-emission fuel that could replace traditional fossil fuels, playing a key role in the transition towards a more sustainable economy. At present, hydrogen-powered cars are already spread worldwide and the deployment of hydrogen buses seems to be the next goal in the decarbonization process of the transportation sector. In contrast with the undeniable benefits introduced by the use of this alternative fuel, given its hazardous properties, safety is a topic of high concern. The present study concerns the evaluation of the risks linked to the on board storage of hydrogen on hydrogen-powered buses in case of road accident. Currently, hydrogen can be stored on board as a high-pressure gas, as a cryogenic liquid or in cryo-compressed form. Those solutions are compared from a safety point of view. First, the final accidental scenarios that could follow the release of the fuel in case of a road crash are pointed out. Secondly, threshold values for the hazardous effects of each scenario are fixed and the corresponding damage distances are calculated thanks to the use of the software PHAST 8.4. Finally, indicators are quantified to compare the different options. Results are discussed to find out the safer solution and to evaluate whether the replacement of fossil fuels with hydrogen introduces new safety issues.

A framework for the environmental risk assessment of offshore carbon storage in CCS systems

Carbon capture and storage (CCS) represents an interesting climate mitigation option, however, as for any other human activity, there is the impelling need to assess and manage the associated risks. This study specifically addresses the marine environmental risk posed by CO2 leakages associated to CCS subsea engineering system, meant as offshore pipelines and injection / plugged and abandoned wells. The aim of this thesis work is to start approaching the development of a complete and standardized practical procedure to perform a quantified environmental risk assessment for CCS, with reference to the specific activities mentioned above. Such an effort would be of extreme relevance not only for companies willing to implement CCS, as a methodological guidance, but also, by uniformizing the ERA procedure, to begin changing people’s perception about CCS, that happens to be often discredited due to the evident lack of comprehensive and systematic methods to assess the impacts on the marine environment. The backbone structure of the framework developed consists on the integration of ERA’s main steps and those belonging to the quantified risk assessment (QRA), in the aim of quantitatively characterizing risk and describing it as a combination of magnitude of the consequences and their frequency. The framework developed by this work is, however, at a high level, as not every single aspect has been dealt with in the required detail. Thus, several alternative options are presented to be considered for use depending on the situation. Further specific studies should address their accuracy and efficiency and solve the knowledge gaps emerged, in order to establish and validate a final and complete procedure. Regardless of the knowledge gaps and uncertainties, that surely need to be addressed, this preliminary framework already finds some relevance in on field applications, as a non-stringent guidance to perform CCS ERA, and it constitutes the foundation of the final framework.

Life cycle assessment (LCA) of a bio-fuel cell fed with waste biomass: potential for scale-up and process optimization

In this Thesis, a life cycle analysis (LCA) of a biofuel cell designed by a team from the University of Bologna was done. The purpose of this study is to investigate the possible environmental impacts of the production and use of the cell and a possible optimization for an industrial scale-up. To do so, a first part of the paper was devoted to studying the present literature on biomass, and fuel cell treatments and then LCA studies on them. The experimental part presents the work done to create the Life Cycle Inventory and Life Cycle Impact Assessment. Several alternative scenarios were created to study process optimization. Reagents and energy supply were changed. To examine whether this technology can be competitive, a comparison was made with some biofuel cell use scenarios with traditional biomass treatment technologies. The result of this study is that this technology is promising from an environmental point of view in case it is possible to recover nutrients in output, without excessive energy consumption, and to minimize the use of energy used to prepare the solution.