Termoconversão do sistema caulinar da mandioca para a obtenção de bioprodutos de valor agregado

Abstract

There is increasing interest in the use of residual lignocellulosic biomass to produce biomaterials, biofuels, and renewable chemicals due to its high availability and low cost. In this context, the residual biomass from cassava harvesting has been proposed as a potential source of raw material for environmentally and economically valuable products. This study evaluated the pyrolysis of biomass from the cassava shoot system (SCM), which includes the aerial parts of the plant and the rhizome, at temperatures of 400, 500, and 600 °C, and characterized the thermoconversion products. The highest yields of biooil (12.6%) and pyrolytic gas (34.1%) were achieved at 600 °C, while biochar reached a maximum yield of 38.9% at 400 °C. Immediate and elemental analyses revealed an increase in the degree of carbonization, aromaticity, and calorific value of the biochar produced at higher temperatures, associated with a decrease in organic functionalization observed by FTIR. De-functionalization, together with an increase in the inorganic content of the biochar, raised the pH from 5.6 to 9.17 and, when applied to soil, BC600C most effectively improved field capacity and water retention at the application rate of 50 tons ha−1. From the biochar granulation process, a soil fertilizer with up to 12.2% urea was produced, which benefited the initial development of corn plants by providing the necessary nutrition and stimulating growth when applied at the appropriate rate, equivalent to 100 kg of N ha−1. The pyrolysis temperature also affected the composition of the liquid products, resulting in the de-functionalization of BO600C as observed by FTIR analysis, which was reflected in the lower total acidity index of this biooil (68 mg KOH g−1). BO400C and BO500C had the highest carbon and lowest oxygen contents, with BO500C having the highest total phenolic content, ~41% EAG, confirmed by GC/MS analysis (33.8% of the total area), followed by carboxylic acids (15.5%) and alcohols (9.9%). The chemical characterization by (−)FT-Orbitrap MS highlighted the presence of classes O2‒7, mainly phenolic compounds. In the positive mode, the predominant constituents were from the Ny and OxNy classes, mainly from the thermal degradation of proteins. Among the pyrolysis products, SCM bio-oils, especially BO500C and BO600C, proved to be promising sources of renewable phenolic compounds, which can be integrated into the chemical industry to replace fossil derivatives. As for the biochar, among iv its many technological applications, it can be used to condition the soil and improve its hydrological characteristics. Additionally, biochar serves as an effective method for carbon sequestration and is also potentially valuable raw material for the production of controlled-release fertilizers.