Digestão anaeróbia de bagaço de cana-de-açúcar: otimização de parâmetros operacionais de pré-tratamento alcalino

Abstract

Sugarcane is the most traded crop in the world and Brazil is the largest global producer. Sugarcane processing generates about 28% of waste in the form of bagasse (SB) with only 50% being used to generate energy from burning in the industries themselves. BC is a lignocellulosic substrate that, if pretreated, can be easily converted into biogas from anaerobic digestion. However, the application of pretreatments on a full scale is limited due to the lack of optimal parameters (chemical concentration and pretreatment time). This study evaluated the alkaline pretreatmentof SBon the Biochemical Methane Potential (BMP) and estimated ideal operational conditions for pretreatment. The SBwas pretreated with NaOH and KOH solutions with different concentrations between 1% and 10% (w/v) and contact times between 1 h and 12 h. The BMP for SBwith and without pretreatment was evaluated in batch mode with 125 mL bottles and an inoculum/substrate ratio of 3. The estimate of optimal pretreatment conditions was obtained through empirical statistical modeling. After generating the models, validation of predicted and observed values were performed. BMP for SBwithout pretreatment varied between 297-306 LNCH4kg VS-1and pretreatment with KOH and NaOH resulted in production values 19% and 20% higher. The optimum operating conditions were 7.7% and 8.3% for NaOH and KOH and contact time of about 12 h, being similar for both solutions. The statistical design indicated that concentrations between 4% and 10% NaOH and 6% and 10% KOH with the optimized contact time result in statistically similar BMP. The validation of the mathematical model indicated a satisfactory adjustment of the results predicted and observed with errors of only 4.5% for the NaOH model and 5.2% for the KOH. In this sense, the optimization of the pretreatment conditions allows a betterfull-scale processapplication because it allows the use of smaller quantities of chemical products and increased methane production.