Water is an indispensable resource for all known forms of life. It covers around 70% of our planet’s surface, mostly in seas and oceans. Only 2.5% of the worlds water resources is available as freshwater with a distribution that is not ubiquitous due to spatiotemporal variability. That notwithstanding, barely 1% of the freshwater resource is available for consumption since a substantial portion of it is frozen in glaciers and polar ice caps. This signifies pressure on the available resource resulting from global population growth and industrial development leading to increase in freshwater consumption. In the present day, water scarcity is already a far-reaching problem that our societies are facing. As a result, the water footprint (WF) concept developed by Hoekstra and Hung (2002) as an indicator for quantifying water use has become a vital pillar to ameliorate the situation. A comprehensive literature review was conducted to analyse and better understand the WF concept. The WF concept was introduced and the different WF terminologies were defined, two main WF frameworks were discussed and a comparison between them was also done. An overview of water flows from the inventory and the main impact mechanisms related to water were highlighted. Furthermore, a general description of WF accounting methods was done by explaining several inventory databases and methods. Adopting the inside-out perspective, a total of 15 pre-selected computational WF methods were then classified into three main groups i.e., 9 water depletion methods, 3 future efforts methods and 3 thermodynamic accounting methods, based on the underlying impact mechanisms and the water use issues addressed. These WF methods were reviewed and then split into two groups based on their levels on the impact pathway i.e., midpoint and endpoint methods. The two groups were thereafter summarized in a tabular format by considering the fundamental elements: the scope of the method and modelling choices, sources of documentation / data, temporal representativeness, geographical representativeness, and main limitations. Following an explicitly stated criteria, five (5) midpoint methods that only assess the impact category of water scarcity, and that are already available to be used in LCA software (SimaPro) were selected for case study application. The selected methods considered most suitable for case study application were: Pfister et al., 2009; Boulay et al., 2011b; Hoekstra et al., 2012; Berger et al., 2014 and AWARE method (2016). These methods used the same units (m3) despite having different characterisation factors (CFs), this simplified comparison of results from the case study. The beneficiation process of Manganese (Mn) ores available in the ecoinvent module was selected as a case study to better understand the environmental impacts of water use as a result of this process considering different WF methods and geographical locations. The cradle-to-gate WF analysis was conducted on the case study using the 5 selected WF midpoint methods. The total scores from the indicators of all the methods influenced by their respective CFs were interpreted, followed by the identification of WF hotspots. The spatial variation of the results was tested by considering Poland (Europe) and Gabon (Africa). Sensitivity analyses were performed using three different calculation set ups created by the modification of the WF inventory and CFs of the WF methods to evaluate the reliability of results. All the 5 WF impact assessment methods showed that WF was higher in Poland than Gabon, and both country-specific WF results were lower than the global reference set up. The results from the WF analysis of the case study were then used to make conclusions and recommendations for future developments and research.
L'acqua è una risorsa indispensabile per tutte le forme di vita conosciute. Copre circa il 70% della superficie del nostro pianeta, principalmente nei mari e negli oceani. Solo il 2,5% delle risorse idriche mondiali è disponibile come acqua dolce con una distribuzione che non è onnipresente a causa della variabilità spazio-temporale. Ciò nonostante, appena l'1% della risorsa di acqua dolce è disponibile per il consumo poiché una parte sostanziale di essa è congelata nei ghiacciai e nelle calotte polari. Ciò significa pressione sulla risorsa disponibile derivante dalla crescita della popolazione globale e dallo sviluppo industriale che porta ad un aumento del consumo di acqua dolce. Al giorno d'oggi, la scarsità d'acqua è già un problema di vasta portata che le nostre società stanno affrontando. Di conseguenza, il concetto di impronta idrica (WF) sviluppato da Hoekstra e Hung (2002) come indicatore per quantificare l'uso dell'acqua è diventato un pilastro fondamentale per migliorare la situazione. È stata condotta una revisione completa della letteratura per analizzare e comprendere meglio il concetto di WF. È stato introdotto il concetto di WF e sono state definite le diverse terminologie di WF, sono stati discussi due framework principali di WF ed è stato anche fatto un confronto tra di loro. È stata evidenziata una panoramica dei flussi d'acqua dall'inventario e dei principali meccanismi di impatto relativi all'acqua. Inoltre, è stata eseguita una descrizione generale dei metodi contabili WF spiegando diversi database e metodi di inventario. Adottando la prospettiva rovesciata, un totale di 15 metodi computazionali WF preselezionati sono stati quindi classificati in tre gruppi principali, ovvero 9 metodi di esaurimento dell'acqua, 3 metodi di sforzi futuri e 3 metodi di contabilità termodinamica, basati sui meccanismi di impatto sottostanti e l'acqua utilizzare i problemi risolti. Questi metodi WF sono stati rivisti e poi suddivisi in due gruppi in base ai loro livelli sul percorso dell'impatto, ovvero metodi midpoint ed endpoint. I due gruppi sono stati successivamente sintetizzati in formato tabellare considerando gli elementi fondamentali: ambito del metodo e scelte modellistiche, fonti di documentazione / dati, rappresentatività temporale, rappresentatività geografica e principali limitazioni. Seguendo un criterio esplicitamente dichiarato, cinque (5) metodi intermedi che valutano solo la categoria di impatto della scarsità d'acqua e che sono già disponibili per essere utilizzati nel software LCA (SimaPro) sono stati selezionati per l'applicazione del caso di studio. I metodi selezionati considerati più idonei per l'applicazione dei casi di studio sono stati: Pfister et al., 2009; Boulay et al., 2011b; Hoekstra et al., 2012; Berger et al., 2014 e il metodo AWARE (2016). Questi metodi utilizzavano le stesse unità (m3) nonostante avessero diversi fattori di caratterizzazione (CF), questo confronto semplificato dei risultati dal caso di studio. Il processo di arricchimento dei minerali Manganese (Mn) disponibili nel modulo ecoinvent è stato selezionato come caso di studio per comprendere meglio gli impatti ambientali dell'uso dell'acqua come risultato di questo processo considerando diversi metodi WF e posizioni geografiche. L'analisi WF dalla culla al cancello è stata condotta sul caso di studio utilizzando i 5 metodi del punto medio WF selezionati. Sono stati interpretati i punteggi totali degli indicatori di tutti i metodi influenzati dai rispettivi CF, seguiti dall'identificazione degli hotspot WF. La variazione spaziale dei risultati è stata testata considerando la Polonia (Europa) e il Gabon (Africa). Le analisi di sensibilità sono state eseguite utilizzando tre diverse configurazioni di calcolo create dalla modifica dell'inventario WF e CF dei metodi WF per valutare l'affidabilità dei risultati. Tutti i 5 metodi di valutazione dell'impatto del WF hanno mostrato che il WF era maggiore in Polonia rispetto al Gabon, ed entrambi i risultati del WF specifici per paese erano inferiori al set di riferimento globale. I risultati dell'analisi WF del caso di studio sono stati quindi utilizzati per trarre conclusioni e raccomandazioni per futuri sviluppi e ricerche.
Water footprint : application of different methods to the case study of the beneficiation process of manganese ores
NYERO, EMMANUEL
2020/2021
Abstract
Water is an indispensable resource for all known forms of life. It covers around 70% of our planet’s surface, mostly in seas and oceans. Only 2.5% of the worlds water resources is available as freshwater with a distribution that is not ubiquitous due to spatiotemporal variability. That notwithstanding, barely 1% of the freshwater resource is available for consumption since a substantial portion of it is frozen in glaciers and polar ice caps. This signifies pressure on the available resource resulting from global population growth and industrial development leading to increase in freshwater consumption. In the present day, water scarcity is already a far-reaching problem that our societies are facing. As a result, the water footprint (WF) concept developed by Hoekstra and Hung (2002) as an indicator for quantifying water use has become a vital pillar to ameliorate the situation. A comprehensive literature review was conducted to analyse and better understand the WF concept. The WF concept was introduced and the different WF terminologies were defined, two main WF frameworks were discussed and a comparison between them was also done. An overview of water flows from the inventory and the main impact mechanisms related to water were highlighted. Furthermore, a general description of WF accounting methods was done by explaining several inventory databases and methods. Adopting the inside-out perspective, a total of 15 pre-selected computational WF methods were then classified into three main groups i.e., 9 water depletion methods, 3 future efforts methods and 3 thermodynamic accounting methods, based on the underlying impact mechanisms and the water use issues addressed. These WF methods were reviewed and then split into two groups based on their levels on the impact pathway i.e., midpoint and endpoint methods. The two groups were thereafter summarized in a tabular format by considering the fundamental elements: the scope of the method and modelling choices, sources of documentation / data, temporal representativeness, geographical representativeness, and main limitations. Following an explicitly stated criteria, five (5) midpoint methods that only assess the impact category of water scarcity, and that are already available to be used in LCA software (SimaPro) were selected for case study application. The selected methods considered most suitable for case study application were: Pfister et al., 2009; Boulay et al., 2011b; Hoekstra et al., 2012; Berger et al., 2014 and AWARE method (2016). These methods used the same units (m3) despite having different characterisation factors (CFs), this simplified comparison of results from the case study. The beneficiation process of Manganese (Mn) ores available in the ecoinvent module was selected as a case study to better understand the environmental impacts of water use as a result of this process considering different WF methods and geographical locations. The cradle-to-gate WF analysis was conducted on the case study using the 5 selected WF midpoint methods. The total scores from the indicators of all the methods influenced by their respective CFs were interpreted, followed by the identification of WF hotspots. The spatial variation of the results was tested by considering Poland (Europe) and Gabon (Africa). Sensitivity analyses were performed using three different calculation set ups created by the modification of the WF inventory and CFs of the WF methods to evaluate the reliability of results. All the 5 WF impact assessment methods showed that WF was higher in Poland than Gabon, and both country-specific WF results were lower than the global reference set up. The results from the WF analysis of the case study were then used to make conclusions and recommendations for future developments and research.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/175892