Multi-Scale Minero-Chemical Analysis of Biomass Ashes: A Key to Evaluating Their Dangers vs. Benefits

Paola Comodi, Azzurra Zucchini, Umberto Susta, Costanza Cambi, Riccardo Vivani, Gianluca Cavalaglio and Franco Cotana
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Paola Comodi: Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06121 Perugia, Italy
Azzurra Zucchini: Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06121 Perugia, Italy
Umberto Susta: UOC PSAL, AUSL Umbria 1, 06127 Perugia, Italy
Costanza Cambi: Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06121 Perugia, Italy
Riccardo Vivani: Dipartimento di Scienze Farmaceutiche, Università degli Studi di Perugia, 06121 Perugia, Italy
Gianluca Cavalaglio: Dipartimento di Giurisprudenza, Università Telematica Pegaso, 80132 Napoli, Italy
Franco Cotana: Dipartimento di Ingegneria, Università degli Studi di Perugia, 06121 Perugia, Italy

Sustainability, 2021, vol. 13, issue 11, 1-16

Abstract: A multi-methodic analysis was performed on five samples of fly ashes coming from different biomasses. The aim of the study was to evaluate their possible re-use and their dangerousness to people and the environment. Optical granulometric analyses indicated that the average diameter of the studied fly ashes was around 20 µm, whereas only ~1 vol% had diameters lower that 2.5 µm. The chemical composition, investigated with electron probe microanalysis, indicated that all the samples had a composition in which Ca was prevalent, followed by Si and Al. Large contents of K and P were observed in some samples, whereas the amount of potentially toxic elements was always below the Italian law thresholds. Polycyclic aromatic hydrocarbons were completely absent in all the samples coming from combustion plants, whereas they were present in the fly ashes from the gasification center. Quantitative mineralogical content, determined by Rietveld analysis of X-ray powder diffraction data, indicated that all the samples had high amorphous content, likely enriched in Ca, and several K and P minerals, such as sylvite and apatite. The results obtained from the chemo-mineralogical study performed make it possible to point out that biomass fly ashes could be interesting materials (1) for amendments in clayey soils, as a substitution for lime, to stimulate pozzolanic reactions and improve their geotechnical properties, thus, on the one hand, avoiding the need to mine raw materials and, on the other hand, re-cycling waste; and (2) as agricultural fertilizers made by a new and ecological source of K and P.

Keywords: biomass; fly ashes; X-ray diffraction; chemical analysis; multi-methodic analysis (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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