In Italy, the amount of compostable bioplastics (fulfilling the technical standard UNI EN 13432:2002) collected with the organic waste is constantly growing (+160% in the last three years). According to the Italian legislation, these items must be accepted by all biological treatment plants (both aerobic and anaerobic). Anyway, the standard requires only the assessment of the aerobic degradability, while it is generally not necessary to test the behaviour under anaerobic conditions. This aspect is evaluated in the present thesis, with the assessment of the anaerobic degradability of bioplastic bags for the food waste collection (typically employed in Italy for this purpose). First, BMP (Biochemical Methane Potential) tests were performed on four commercial types of bioplastic bags, including both bags specifically designed for the food waste collection and shoppers, that can be reused for the same purpose. Subsequently, two bags were subjected to semi-continuous co-digestion tests together with the food waste, in which their anaerobic degradability was evaluated according to the methane production and the physical status of residues. The tests were performed comparing the behaviour of bioplastic bags to that of a paper bag specifically designed for the food waste collection. Finally, tests to evaluate the influence of physical phenomena (e.g. heat effect on bags, hydrophobicity or hydrophilicity of bags) on the degradation of bioplastics were performed to better understand the results of biological tests. BMP tests indicated a good degradability (>71%) of bioplastic bags, while semi-continuous tests (more similar to the real operation in full-scale anaerobic digestion plants) showed a low degradability (<27%), confirmed by the physical status of the undigested bag pieces. Moreover, a very different behaviour was observed in semi-continuous tests for the two different tested bioplastic bags, at least partially explained by the effect of physical factors on bags. On the contrary, very interesting perspectives are offered by the tested paper bag, since its degradability in the semi-continuous tests (82%) resulted even higher than that observed in the BMP tests (74%).
In Italia, la quantità di bioplastiche compostabili (conformi allo standard tecnico UNI EN 13432:2002) raccolte con il rifiuto organico è in costante crescita (+160% negli ultimi tre anni). La legislazione italiana prevede che questi manufatti debbano essere accettati da tutti gli impianti di trattamento biologico, siano essi aerobici o anaerobici. Tuttavia, lo standard richiede la sola valutazione della degradabilità aerobica, mentre non è generalmente necessario testare il comportamento in condizioni anaerobiche. Questo aspetto è analizzato nel presente lavoro di tesi, con la valutazione della degradabilità anaerobica di uno specifico manufatto in bioplastica, ovvero i sacchetti utilizzati per la raccolta del rifiuto alimentare, il cui utilizzo è ampiamente diffuso in Italia. Sono state innanzitutto eseguite prove di biometanazione (BMP - Biochemical Methane Potential) su quattro tipologie di sacchetti in bioplastica, includendo sia quelli specificamente progettati per la raccolta del rifiuto alimentare sia gli shopper, che possono essere riutilizzati allo stesso scopo dopo il primo utilizzo per il contenimento della spesa. Successivamente, due tipologie di sacchetti sono state sottoposte a prove di co-digestione con il rifiuto alimentare in condizioni di alimentazione in semi-continuo, nelle quali la loro degradabilità anaerobica è stata valutata sulla base della produzione di metano e dello stato fisico dei residui. Le prove sono state effettuate confrontando il comportamento dei sacchetti in bioplastica con quello di sacchetti in carta specificamente realizzati per la raccolta del rifiuto alimentare. Infine, per meglio interpretare i risultati delle prove biologiche, sono state eseguite prove per valutare l’influenza di fenomeni fisici (quali l’effetto del calore sui sacchetti e l’idrofobia o idrofilia dei sacchetti) sulla degradazione delle bioplastiche. Le prove di BMP indicano una buona degradabilità (>71%) dei sacchetti in bioplastica, mentre le prove in semi-continuo (che più simulano la gestione negli impianti a scala reale) mostrano una degradabilità molto ridotta (<27%), confermata dallo stato fisico dei pezzi di sacchetto non digeriti. Inoltre, è stato osservato un comportamento molto differente nelle prove in semi-continuo per i due sacchetti in bioplastica testati, almeno parzialmente dovuto all’effetto dei fattori fisici sui sacchetti. Al contrario, prospettive molto interessanti sono offerte dal sacchetto in carta, la cui degradabilità anaerobica nelle prove in semi-continuo (82%) risulta anche superiore a quella osservata nelle prove di BMP (74%).
Analisi sperimentale sulla degradazione anaerobica di sacchetti in carta e in bioplastica per la raccolta del rifiuto alimentare
Venturelli, Valeria
2019/2020
Abstract
In Italy, the amount of compostable bioplastics (fulfilling the technical standard UNI EN 13432:2002) collected with the organic waste is constantly growing (+160% in the last three years). According to the Italian legislation, these items must be accepted by all biological treatment plants (both aerobic and anaerobic). Anyway, the standard requires only the assessment of the aerobic degradability, while it is generally not necessary to test the behaviour under anaerobic conditions. This aspect is evaluated in the present thesis, with the assessment of the anaerobic degradability of bioplastic bags for the food waste collection (typically employed in Italy for this purpose). First, BMP (Biochemical Methane Potential) tests were performed on four commercial types of bioplastic bags, including both bags specifically designed for the food waste collection and shoppers, that can be reused for the same purpose. Subsequently, two bags were subjected to semi-continuous co-digestion tests together with the food waste, in which their anaerobic degradability was evaluated according to the methane production and the physical status of residues. The tests were performed comparing the behaviour of bioplastic bags to that of a paper bag specifically designed for the food waste collection. Finally, tests to evaluate the influence of physical phenomena (e.g. heat effect on bags, hydrophobicity or hydrophilicity of bags) on the degradation of bioplastics were performed to better understand the results of biological tests. BMP tests indicated a good degradability (>71%) of bioplastic bags, while semi-continuous tests (more similar to the real operation in full-scale anaerobic digestion plants) showed a low degradability (<27%), confirmed by the physical status of the undigested bag pieces. Moreover, a very different behaviour was observed in semi-continuous tests for the two different tested bioplastic bags, at least partially explained by the effect of physical factors on bags. On the contrary, very interesting perspectives are offered by the tested paper bag, since its degradability in the semi-continuous tests (82%) resulted even higher than that observed in the BMP tests (74%).| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/173222