In 2021, 29.6 million tons of municipal waste were generated in Italy, of which more than 30% is organic waste. The organic fraction consists mainly in the food waste and the green fraction, but also non-negligible quantities of cellulosic fractions (142,000 tonnes in 2021) and compostable bioplastics (83,000 tonnes in 2019-2020) were found. The Italian legislation requires that waste, including packaging, with biodegradability and compostability properties (complying with the UNI EN 13432:2002 technical standard) is collected and recycled with organic waste. However, according to the standard, the assessment of anaerobic degradability for the purposes of compostability certification is not mandatory. Based on the growing diffusion of compostable bioplastics and paper products and of the amount of food waste managed in anaerobic digestion plants, the objective of this thesis was the evaluation of the degradability, under anaerobic conditions, of two paper-based packaging items for takeaway food (one box made of paper only and another box made of paper with a polylactic acid - PLA film). Biochemical methane potential (BMP) tests were conducted in mono-digestion on the two boxes and on food waste. The paper-only box demonstrated a behaviour comparable to that of food waste, reaching a degradability higher than 90%. The box composed of paper (91%) and PLA (9%), was instead characterised by a lower degradability (76%). The interest focused on the evaluation of the behaviour of the latter, on which co-digestion with food waste was performed in BMP and semi-continuous tests, to simulate anaerobic digestion conditions at real scale. The proportion between the two substrates was chosen equal to the national quantity of cellulosic fractions disposed of with food waste (2.5% by weight). At the end of the BMP co-digestion test, no noteworthy residues were identified and a degradability value of the mixture equal to 90% was obtained. This degradability value was also confirmed by semi-continuous co-digestion tests, in which the presence of undigested residues was not negligible. These residues mainly consist of PLA, and it was possible to calculate that the non-degraded PLA at the end of the tests corresponds to 30% of the weight of PLA fed to the system.
L’Italia, nel 2021, ha prodotto 29,6 milioni di tonnellate di rifiuti urbani, di cui più del 30% è costituito dal rifiuto organico. La frazione organica è costituita principalmente dalla frazione alimentare e dalla frazione verde, ma al suo interno in quantità non trascurabili si ritrovano anche le frazioni cellulosiche (142000 tonnellate nel 2021) e le bioplastiche compostabili (83000 tonnellate nel periodo 2019-2020). La legislazione nazionale prevede che i rifiuti, anche di imballaggi, aventi proprietà di biodegradabilità e compostabilità (conformi allo standard tecnico UNI EN 13432:2002) siano raccolti e riciclati con il rifiuto organico. Lo standard, tuttavia, non prevede l’obbligatorietà della valutazione della degradabilità anaerobica ai fini della certificazione di compostabilità. Sulla base della crescente diffusione sul mercato dei manufatti in bioplastica e carta compostabili e della continua crescita della quantità di rifiuto alimentare trattata in impianti anaerobici, l’obiettivo di questo lavoro di tesi è stato la valutazione della degradabilità in condizioni anaerobiche di due imballaggi a base carta per il cibo d’asporto (uno realizzato in sola carta e l’altro realizzato in carta con un film in acido polilattico - PLA), quando sottoposti ai processi di trattamento del rifiuto organico di tipo anaerobico. Sono state effettuate prove di bio-metanazione (BMP) in mono-digestione sui due imballaggi e sul rifiuto alimentare; la vaschetta in sola carta ha dimostrato un comportamento paragonabile a quello del rifiuto alimentare, riscontrando per entrambi una degradabilità superiore al 90%. La vaschetta composta da carta (91%) e uno strato di PLA (9%), è stata invece caratterizzata da un valore di degradabilità inferiore, pari al 76%. L’interesse si è quindi focalizzato sulla valutazione del comportamento della vaschetta realizzata con film in PLA, su cui è stata testata la co-digestione con rifiuto alimentare in prove di BMP e alimentazione semi-continua, per simulare le condizioni di digestione anaerobica alla scala reale. La proporzione tra i due substrati è stata scelta pari al quantitativo nazionale di frazioni cellulosiche smaltite con il rifiuto alimentare (2,5% in peso). Al termine della prova di BMP in co-digestione non sono stati individuati residui degni di nota e si è ottenuto un valore di degradabilità della miscela pari al 90%. Tale valore di degradabilità è stato confermato anche dalle prove di co-digestione in alimentazione semi-continua, in cui tuttavia si è riscontrata la presenza di residui non digeriti. Tali residui sono costituiti principalmente da PLA ed è stato possibile calcolare che il PLA non degradato corrisponde al 30% del peso totale di PLA alimentato.
Analisi sperimentale sulla degradazione anaerobica di vaschette a base carta per il cibo d'asporto
Intilisano, Martina
2022/2023
Abstract
In 2021, 29.6 million tons of municipal waste were generated in Italy, of which more than 30% is organic waste. The organic fraction consists mainly in the food waste and the green fraction, but also non-negligible quantities of cellulosic fractions (142,000 tonnes in 2021) and compostable bioplastics (83,000 tonnes in 2019-2020) were found. The Italian legislation requires that waste, including packaging, with biodegradability and compostability properties (complying with the UNI EN 13432:2002 technical standard) is collected and recycled with organic waste. However, according to the standard, the assessment of anaerobic degradability for the purposes of compostability certification is not mandatory. Based on the growing diffusion of compostable bioplastics and paper products and of the amount of food waste managed in anaerobic digestion plants, the objective of this thesis was the evaluation of the degradability, under anaerobic conditions, of two paper-based packaging items for takeaway food (one box made of paper only and another box made of paper with a polylactic acid - PLA film). Biochemical methane potential (BMP) tests were conducted in mono-digestion on the two boxes and on food waste. The paper-only box demonstrated a behaviour comparable to that of food waste, reaching a degradability higher than 90%. The box composed of paper (91%) and PLA (9%), was instead characterised by a lower degradability (76%). The interest focused on the evaluation of the behaviour of the latter, on which co-digestion with food waste was performed in BMP and semi-continuous tests, to simulate anaerobic digestion conditions at real scale. The proportion between the two substrates was chosen equal to the national quantity of cellulosic fractions disposed of with food waste (2.5% by weight). At the end of the BMP co-digestion test, no noteworthy residues were identified and a degradability value of the mixture equal to 90% was obtained. This degradability value was also confirmed by semi-continuous co-digestion tests, in which the presence of undigested residues was not negligible. These residues mainly consist of PLA, and it was possible to calculate that the non-degraded PLA at the end of the tests corresponds to 30% of the weight of PLA fed to the system.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/210460