Análise da fração líquida e sólida a partir do pré-tratamento da biomassa do sorgo sacarino

Abstract

In a post-pandemic scenario of high inflation, the current war between Russia and Ukraine, affecting the entire world market, which has been suffering from the scarcity and authoritarian control of oil-derived fuels, and its consequent rise in prices, makes the eyes turn to new energy sources, in order to diversify its matrix in a clean and renewable way. Within this objective, second-generation ethanol, using sweet sorghum biomass (Sorghum bicolor) as a raw material, becomes attractive due to several factors, such as large amounts of intrinsic cellulose and hemicellulose, which can be converted into ethanol, short cycle production and because it is discarded as agricultural residue in Brazil, due to its use as a ground cover plant in the period between harvests. The challenge takes place in the first stage of the process, called pretreatment, which is intended to break down the lignin present in the biomass, which works as a barrier and prevents the release of content with the potential to be transformed into ethanol in later stages. In this work, several basic chemical agents were used in the pretreatment step, such as sodium hydroxide, calcium hydroxide, calcium oxide, calcium carbonate, potassium hydroxide and hydrogen peroxide, in the fractions of 5% and 15% (w/w), together with 10 grams of biomass and 100 mL of water stirred for 24 hours at 70 ºC and 200 rpm, to carry out a preliminary study in order to understand the behavior and the best chemical agents in the breakdown of sorghum biomass lignin. After the preliminary stage, a new round of studies was carried out with the combination of two consecutive pre-treatments, fixing the chemical agents at 5% concentration. The liquid fractions were analyzed in order to verify the behavior of both and it can be seen that high concentrations of chemical agent can degrade glucose and other compounds present in the liquid fraction, mainly in the pretreatment in two stages, where most of the compounds was degraded, but it is more efficient in the removal of lignin in the solid fraction, where the pre-treatment with 15% CaO (w/w) removed 75.29% of the lignin and maintaining 90.86% of the cellulose compared to biomass in natura, which must be considered when one wants to increase efficiency using the two fractions for the subsequent production of ethanol.