Development of an innovative pyrolysis plant for the production of secondary raw materials

This project was born with the aim of developing an environmentally and financially sustainable process to dispose of end-life tires. In this perspective was devised an innovative static bed batch pilot reactor where pyrolysis can be carried out on the whole tires in order to recover energy and materials and simultaneously save the energy costs of their shredding. The innovative plant is also able to guarantee a high safety of the process thanks to the presence of a hydraulic guard. The pilot plant was used to pyrolyze new and end-life tires at temperatures from 400 to 600°C with step of 50°C in presence of steam. The main objective of this research was to evaluate the influence of the maximum process temperature on yields and chemical-physics properties of pyrolysis products. In addition, in view of a scale-up of the plant in continuous mode, the influence of the nature of several different tires as well as the effects of the aging on the final products were studied. The same pilot plant was also used to carry out pyrolysis on polymeric matrix composites in order to obtain chemical feedstocks from the resin degradation together with the recovery of the reinforcement in the form of fibers. Carbon fibers reinforced composites ad fiberglass was treated in the 450-600°C range and the products was fully characterized. A second oxidative step was performed on the pyrolysis solid residue in order to obtain the fibers in a suitable condition for a subsequent re-impregnation in order to close the composite Life Cycle in a cradle-to-cradle approach. These investigations have demonstrated that steel wires, char, carbon and glass fibers recovered in the prototypal plant as solid residues can be a viable alternative to pristine materials, making use of them to obtain new products with a commercial added value.

Molecular markers for the assessment of genetic variability in threatened plant species

La variabilità genetica è un importante strumento per lo studio e la conservazione della biodiversità in specie rare e minacciate di estinzione. Durante il mio dottorato mi sono quindi occupata di mettere a punto diverse metodologie molecolari al fine di valutare la diversità genetica in due specie rare della flora italiana che presentano problematiche diverse e specifiche. I marcatori arbitrari RAPD e i marcatori semi-arbitrari ISSR sono stati utilizzati per valutare la diversità genetica in Quercus crenata Lam. e per confermare l’ipotesi della sua origine ibridogena dalle due specie presunte parentali Quercus cerris L. e Quercus suber L., essendo Q. crenata presente in Italia settentrionale dove Q. suber è attualmente assente. I marcatori SSR o microsatelliti sono invece stati messi a punto su una specie a rischio di estinzione, endemica dell’Appennino Tosco-Emiliano, Primula apennina Widmer, applicando una metodologia specifica, basata sulla costruzione di una libreria genomica arricchita per l’isolamento di primer specifici. I marcatori RAPD e ISSR, utilizzati su un totale di 85 campioni, hanno mostrato alti livelli di diversità molecolare entro le specie studiate, eccetto per Q. suber le cui popolazioni rappresentano il margine orientale di distribuzione della specie, per questo più sottoposte ad impoverimento genetico. Oltre alla cluster analysis (UPGMA) e alla Analisi delle Componenti Principali effettuate per entrambi i marcatori, che confermano l’ipotesi dell’origine ibrida degli individui di Q. crenata diffusi in Italia Settentrionale, sono stati calcolati l’indice di ibridità basato sul maximum likelihood, che dimostra una introgressione asimmetrica di Q. crenata verso il parentale caratterizzato da superiorità demografica (Q. cerris) e il test di Mantel. Quest’ultimo ha permesso di confrontare i due marcatori RAPD e ISSR utilizzati ottenendo una bassa correlazione, a conferma del fatto che, amplificando tratti differenti del DNA nucleare, i dati non sono sovrapponibili, sebbene forniscano risultati analoghi. Per l’isolamento di loci microsatelliti ipervariabili ho utilizzato il protocolllo FIASCO (Fast isolation by AFLP of sequences containing repeats- Zane et al. 2002) che permette di costruire una libreria genomica arricchita partendo dal DNA estratto da P. apennina. Tale procedura ha previsto la digestione del DNA genomico per la produzione di una miscela di frammenti di DNA. Tramite ibridazione con opportune sonde sono stati isolati i frammenti contenenti i microsatelliti. Sequenziando i cloni ricombinanti, ho ottenuto sequenze contenenti repeats sulle cui regioni fiancheggianti sono stati costruiti 15 coppie di primer che potranno, in seguito, essere utilizzate per definire la quota di riproduzione clonale in P. apennina e per valutare la diversità genetica delle popolazioni che coprono l’areale di distribuzione della specie. Data la loro natura altamente variabile e la loro abbondanza nel DNA, gli SSR saranno, come i marcatori RAPD e gli ISSR, ugualmente validi per lo studio della variabilità genetica e per l’analisi di problematiche specifiche legate alle specie rare.

Changes in plant metabolism induced by dioxygenase inhibitors and their effect on the epiphytic microbial community and fire blight (Erwinia amylovora) control

Fire blight, caused by the gram negative bacterium Erwinia amylovora, is one of the most destructive bacterial diseases of Pomaceous plants. Therefore, the development of reliable methods to control this disease is desperately needed. This research investigated the possibility to interfere, by altering plant metabolism, on the interactions occurring between Erwinia amylovora, the host plant and the epiphytic microbial community in order to obtain a more effective control of fire blight. Prohexadione-calcium and trinexapac-ethyl, two dioxygenase inhibitors, were chosen as a chemical tool to influence plant metabolism. These compounds inhibit the 2-oxoglutarate-dependent dioxygenases and, therefore, they greatly influence plant metabolism. Moreover, dioxygenase inhibitors were found to enhance plant resistance to a wide range of pathogens. In particular, dioxygenase inhibitors application seems a promising method to control fire blight. From cited literature, it is assumed that these compounds increase plant defence mainly by a transient alteration of flavonoids metabolism. We tried to demonstrate, that the reduction of susceptibility to disease could be partially due to an indirect influence on the microbial community established on plant surface. The possibility to influence the interactions occurring in the epiphytic microbial community is particularly interesting, in fact, the relationships among different bacterial populations on plant surface is a key factor for a more effective biological control of plant diseases. Furthermore, we evaluated the possibility to combine the application of dioxygenase inhibitors with biological control in order to develop an integrate strategy for control of fire blight. The first step for this study was the isolation of a pathogenic strain of E. amylovora. In addition, we isolated different epiphytic bacteria, which respond to general requirements for biological control agents. Successively, the effect of dioxygenase inhibitors treatment on microbial community was investigated on different plant organs (stigmas, nectaries and leaves). An increase in epiphytic microbial population was found. Further experiments were performed with aim to explain this effect. In particular, changes in sugar content of nectar were observed. These changes, decreasing the osmotic potential of nectar, might allow a more consistent growth of epiphytic bacteria on blossoms. On leaves were found similar differences as well. As far as the interactions between E. amylovora and host plant, they were deeply investigated by advanced microscopical analysis. The influence of dioxygenase inhibitors and SAR inducers application on the infection process and migration of pathogen inside different plant tissues was studied. These microscopical techniques, combined with the use of gpf-labelled E. amylovora, allowed the development of a bioassay method for resistance inducers efficacy screening. The final part of the work demonstrated that the reduction of disease susceptibility observed in plants treated with prohexadione-calcium is mainly due to the accumulation of a novel phytoalexins: luteoforol. This 3-deoxyflavonoid was proven to have a strong antimicrobial activity.

Organic fertilization of peach trees: implication on nitrogen availability, root growth and carbon distribution within plant

In the last years, sustainable horticulture has been increasing; however, to be successful this practice needs an efficient soil fertility management to maintain a high productivity and fruit quality standards. For this purpose composted organic materials from agri-food industry and municipal solid waste has been used as a source to replace chemical fertilizers and increase soil organic matter. To better understand the influence of compost application on soil fertility and plant growth, we carried out a study comparing organic and mineral nitrogen (N) fertilization in micro propagated plants, potted trees and commercial peach orchard with these aims: 1. evaluation of tree development, CO2 fixation and carbon partition to the different organs of two-years-old potted peach trees. 2. Determination of soil N concentration and nitrate-N effect on plant growth and root oxidative stress of micro propagated plant after increasing rates of N applications. 3. Assessment of soil chemical and biological fertility, tree growth and yield and fruit quality in a commercial orchard. The addition of compost at high rate was effective in increasing CO2 fixation, promoting root growth, shoot and fruit biomass. Furthermore, organic fertilizers influenced C partitioning, favoring C accumulation in roots, wood and fruits. The higher CO2 fixation was the result of a larger tree leaf area, rather than an increase in leaf photosynthetic efficiency, showing a stimulation of plant growth by application of compost. High concentrations of compost increased total soil N concentration, but were not effective in increasing nitrate-N soil concentration; in contrast mineral-N applications increased linearly soil nitrate-N, even at the lowest rate tested. Soil nitrate-N concentration influenced positively plant growth at low rate (60- 80 mg kg-1), whereas at high concentrations showed negative effects. In this trial, the decrease of root growth, as a response to excessive nitrate-N soil concentration, was not anticipated by root oxidative stress. Continuous annual applications of compost for 10 years enhanced soil organic matter content and total soil N concentration. Additionally, high rate of compost application (10 t ha-1 year-1) enhanced microbial biomass. On the other hand, different fertilizers management did not modify tree yield, but influenced fruit size and precocity index. The present data support the idea that organic fertilizers can be used successfully as a substitute of mineral fertilizers in fruit tree nutrient management, since they promote an increase of soil chemical and biological fertility, prevent excessive nitrate-N soil concentration, promote plant growth and potentially C sequestration into the soil.

Advanced Waste-To-Energy Cycles

The increase in environmental and healthy concerns, combined with the possibility to exploit waste as a valuable energy resource, has led to explore alternative methods for waste final disposal. In this context, the energy conversion of Municipal Solid Waste (MSW) in Waste-To-Energy (WTE) power plant is increasing throughout Europe, both in terms of plants number and capacity, furthered by legislative directives. Due to the heterogeneous nature of waste, some differences with respect to a conventional fossil fuel power plant have to be considered in the energy conversion process. In fact, as a consequence of the well-known corrosion problems, the thermodynamic efficiency of WTE power plants typically ranging in the interval 25% ÷ 30%. The new Waste Framework Directive 2008/98/EC promotes production of energy from waste introducing an energy efficiency criteria (the so-called “R1 formula”) to evaluate plant recovery status. The aim of the Directive is to drive WTE facilities to maximize energy recovery and utilization of waste heat, in order to substitute energy produced with conventional fossil fuels fired power plants. This calls for novel approaches and possibilities to maximize the conversion of MSW into energy. In particular, the idea of an integrated configuration made up of a WTE and a Gas Turbine (GT) originates, driven by the desire to eliminate or, at least, mitigate limitations affecting the WTE conversion process bounding the thermodynamic efficiency of the cycle. The aim of this Ph.D thesis is to investigate, from a thermodynamic point of view, the integrated WTE-GT system sharing the steam cycle, sharing the flue gas paths or combining both ways. The carried out analysis investigates and defines the logic governing plants match in terms of steam production and steam turbine power output as function of the thermal powers introduced.

Analysis and modelling of the performance of technologies for flue gas treatment in Waste-to-Energy processes

Waste management represents an important issue in our society and Waste-to-Energy incineration plants have been playing a significant role in the last decades, showing an increased importance in Europe. One of the main issues posed by waste combustion is the generation of air contaminants. Particular concern is present about acid gases, mainly hydrogen chloride and sulfur oxides, due to their potential impact on the environment and on human health. Therefore, in the present study the main available technological options for flue gas treatment were analyzed, focusing on dry treatment systems, which are increasingly applied in Municipal Solid Wastes (MSW) incinerators. An operational model was proposed to describe and optimize acid gas removal process. It was applied to an existing MSW incineration plant, where acid gases are neutralized in a two-stage dry treatment system. This process is based on the injection of powdered calcium hydroxide and sodium bicarbonate in reactors followed by fabric filters. HCl and SO2 conversions were expressed as a function of reactants flow rates, calculating model parameters from literature and plant data. The implementation in a software for process simulation allowed the identification of optimal operating conditions, taking into account the reactant feed rates, the amount of solid products and the recycle of the sorbent. Alternative configurations of the reference plant were also assessed. The applicability of the operational model was extended developing also a fundamental approach to the issue. A predictive model was developed, describing mass transfer and kinetic phenomena governing the acid gas neutralization with solid sorbents. The rate controlling steps were identified through the reproduction of literature data, allowing the description of acid gas removal in the case study analyzed. A laboratory device was also designed and started up to assess the required model parameters.

Assessing Household Food Waste in Italy: A Methodology for Detecting Drivers and Quantities

It has been estimated that one third of edible food destined for human consumption is lost or wasted along the food supply chain globally. Much of the waste comes from Global North, where consumers are considered as the bigger contributors. Different studies tried to analyze and estimate the Household Food Waste (HFW), especially in UK and Northern Europe. The result is that accurate studies at national level exist only in UK, Finland and Norway while no such studies are available in Italy, except for survey- based researches. Though, there is a widespread awareness that such methods might be not able to estimate Food Waste. Results emerging from literature clearly suggest that survey estimate inferior amounts of Food Waste as a result, if compared to waste sorting and weighting analysis or to diary studies. The hypothesis that household food waste is under-estimated when gathered through questionnaires has been enquired into. First, a literature review of behavioral economics and heuristics has been proposed; then, a literature review of the sector listing the existing methodologies to gather national data on Household Food Waste has been illustrated. Finally, a pilot experiment to test a mixed methodology is proposed. While literature suggests that four specific cognitive biases might be able to affect the reliability of answers in questionnaires, results of the present experiment clearly indicate that there is a relevant difference between how much the individual thinks to waste and he/she actually does. The result is a mixed methodology based on questionnaire, diary and waste sorting, able to overcome the cons of each single method.