Potential of application of biomass ashes in construction materials
CAPELA M. 1, TOBALDI D. 2, TARELHO L. 3, SEABRA M. 1, LABRINCHA J. 1
1 Department of Materials and Ceramic Engineering, CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193, Aveiro, Portugal, Aveiro, Portugal; 2 CNR Nanotec, Institute of Nanotechnology, Campus Ecoteckne, 73100 Lecce, Italy, Lecce, Italy; 3 Department of Environment and Planning, CESAM - Centre for Environmental and Marine Studies, University of Aveiro, 3810-193 Aveiro, Portugal, Aveiro, Portugal
The physicochemical properties of the ash streams generated in biomass thermal power plants can exhibit temporal variability, mainly due to compositional variations in the used fuel blends. This fact can compromise the definition of a potential recycling solution which is essential to the sustainability of the biomass-to-energy practice.
The present work evaluated the potential application of the ashes resulting from the combustion of different biomass typologies used in a Portuguese power plant in construction materials. With that purpose, eucalyptus treetops (ET) and bark (EB), pine treetops (PT), grey willow (W), white poplar (P), silver wattle (SW), and Sydney golden wattle (GW) samples were collected. Next, they were individually incinerated at 825 °C, which is the typical combustion temperature at the thermal power plant. The generated ashes were then characterized in terms of chemical (XRF) and mineralogical (XRD) composition, particle size distribution (laser diffraction), and morphology (SEM).
It was verified that the ash’s characteristics are profoundly dependent on the biomass typologies used as fuel. Moreover, the obtained ashes cannot be used alone as secondary raw material for clinker production, since they exhibit low concentrations of Al2O3 and Fe2O3 and a CaO/SiO2 mass ratio that is, in general, too high. Nevertheless, according to EN197–1:2011 and the obtained Na2O(eq) values, they can be incorporated in cementitious formulations, as cement substitute or as filler, with a maximum incorporation percentage that ranges from 48 wt.% for ET to 100 wt.% for EB, depending on the biomass type.
These results highlight the need for proper management of the biomass fuel blends used to guarantee suitable quality control of the ashes at the power plant to facilitate its further valorisation.
Acknowledgments
This work was developed within the scope of the project CICECO - Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC).