Hydrothermal carbonization as a mild pre-treatment to selectively remove ashes from bamboo biomass

In this work of thesis, a mild hydrothermal treatment of bamboo has been investigated, aimed at the selective solubilization of ashes, which can create relevant problems during direct biomass combustion, such as formation of deposits and particulate matter emissions. Pilot-scale combustion test of pristine bamboo biomass was carried out in a 55-kW fixed bed boiler to evaluate the corresponding pollutant emissions. Subsequently, an optimization study of the hydrothermal treatment was performed at different reaction times (1-4-8 hours) and temperatures (160-180-200 °C), using the constant biomass loading (10 wt%). The thermal processing was optimized to selectively solubilize ashes, at the same time preserving intact the macrostructural composition of the starting biomass. An in-depth characterization of the obtained solid streams was carried out, demonstrating the effectiveness of the proposed approach. Finally, in the perspective of developing an integrated process, the corresponding process liquors were characterised for agronomic properties, to get useful information about possible exploitation as bio-fertilizers.