Chemical and mineralogical characterization and potential use of ash from Amazonian biomasses as an agricultural fertilizer and for soil amendment

ABSTRACT The increasing use of biomass as a biofuel has contributed to the production of a large quantity of ash, which is managed as waste. Biomass ash can be applied to soil as a strategy for recycling this waste, thereby contributing to the sustainable production of biomass. However, variations in the biomass composition, which depend on the biomass type and production conditions, present a difficulty in utilizing the ash. Therefore, the yield and composition of ash produced from the combustion of acai seeds (Euterpe oleracea Mart.) and wood chips by the local fertilizer industry were evaluated in this study to further the understanding and sustainable use of Amazonian biomasses and their ashes. To this end, proximate, ultimate, chemical, and mineralogical analyses were conducted. The results were used to estimate that the fertilizer industry produces ∼4.7 to 9.9 tons/day of ash, which occurs as bottom ash and has a relatively low compositional variability throughout the year. Ash from Amazonian biomasses is mineralogically composed of amorphous phases, silicates, and oxides and chemically composed of SiO2, Al2O3, CaO, Fe2O3, P2O5, K2O, and MgO. The highest quantities of SiO2 and Al2O3 mainly result from quartz and kaolinite incorporated in the biomasses. By contrast, CaO and MgO originate from wood chips, whereas K2O and P2O5 originate from acai seeds. The bottom ash is high in available nutrients, has a moderate neutralizing capacity, and is low in heavy metals. Thus, this ash could be applied to the soil to return nutrients and contribute to sustainable biomass production.