Ashes derived from the combustion of vegetal and animal biomass still represent a mostly unexplored secondary raw material for the production of alkali-activated materials, given their peculiar chemical nature. In this work, calcium phosphate biomass ashes were successfully used as partially reactive fillers in a metakaolin-based geopolymer composite to produce, by direct foaming, sustainable and lightweight boards with thermal insulating properties. The investigated materials were obtained by activating a blend of metakaolin and biomass ash in a weight ratio of 1: 1 and foamed with the addition of H₂O₂ in measure of 5 wt. %, to maximize the volume of disposed ash and ensure adequate properties to the material at the same time. The obtained geopolymer composite was characterized by microstructural, chemical-physical, mechanical and thermal analysis: the obtained results showed that biomass ash and metakaolin well integrated in the microstructure of the final porous material, which was characterized by a density of about 310 kg/m³ and a thermal conductivity of 0.073 W/mK at a mean test temperature of 30 °C, coupled with an acceptable compressive strength of about 0.6 MPa. Dilatometric and thermogravimetric analysis, performed up to 1000 °C, highlighted the thermal stability of the composite, which could be regarded as a promising material for low-cost, self-bearing thermal insulating partitions or lightweight cores for thermostructural sandwich panels.

Ice-templating (freeze-casting) technique was applied to a novel class of geopolymer composites containing Fe/Mn oxides, previously tested and reported in others works as synthetic oxygen carriers for chemical looping combustion (CLC), in order to obtain composite monoliths with lamellar macro-porosities by unidirectional freezing of water-based sol-gel systems. Geopolymer-Fe/Mn oxides composites carriers were also produced as beads, suitable for fixed bed reactors, by an injection-solidification method in liquid nitrogen. After conditioning at 900 °C, the temperature needed for CLC applications, the composite beads and monoliths possess similar total porosity % and total pore volume, being ≈65% and 570 mm³ g⁻¹, respectively, as well as a specific surface area of around 2.4–2.9 m²/g.

The widespread use of natural aggregates is one of the main causes of the depletion of natural resources, as aggregates are constituents of several construction materials. Alternatively, it is, today, proven to be feasible to use mining tailings, either natural or recycled materials, to produce artificial aggregates through specific processes. A possible way to produce artificial aggregate is through the alkali activation of the powdered material in a process called geopolymerization. This study proposes to use a basalt powder and two different metakaolins as precursors for the production of an alkali-activated artificial aggregate, with a specific shape and size achieved by using 3D-printed molds. The experimental aggregates were evaluated using traditional tests for natural aggregates, such as resistance to compression, specific density and resistance to abrasion and fragmentation. Furthermore, the material was chemically analyzed in order to evaluate the geopolymerization process promoted by the two adopted metakaolins. The physical tests showed that artificial aggregates do not perform well in terms of resistance to wear and fragmentation, which can be improved. However, they revealed promising results in terms of skid, polishing and micro-texture.

Biomass residues are often considered as a resource if conveniently converted in fuel and alternative feedstock for chemical processes, and their conversion into valuable products may occur by different pathways. This work is focused on the thermochemical conversion at moderate temperature and in steam atmosphere, a mild process in comparison to hydrothermal liquefaction, followed by extraction of soluble products in a solvent. Such process has been already applied to various residues and here extended to the case of marc, the residual pomace from wine making, largely produced worldwide. A pressurized batch reactor was used for the quantitative determination of produced solid and liquid fractions, and their qualitative characterization was performed by instrumental analyses. The pressurized steam conversion of marc was effective, providing a yield in liquid fraction, upon extraction in solvent, up to 30% of the raw dried biomass. The use of polar and nonpolar solvent for the extraction of the liquid fraction was inspected. Applied operating conditions, namely residence time in the batch reactor and extraction modality, showed a significant influence on the process performance. In particular, long residence and extraction times and use of nonpolar solvent substantially improved the yield in liquid fraction.