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In this work, a mechanistic model was developed to simulate the kinetics of the production of levulinic acid (LA) from sugarcane bagasse (SCB), rice husk (RH) and soybean straw (SS). The production of LA from those agro-industrial wastes followed the methodology of biorefining in three stages. Experimental data from the third stage (catalytic depolymerization of cellulose) obtained under a wide range of operating conditions were used to estimate the parameters of the model. An optimization procedure based on a genetic algorithm was used to determine the optimal parameter values. The prediction of the concentrations of glucose, 5-HMF and LA using the mechanistic model was particularly accurate, as demonstrated by R 2 and RMSE. Thereby, a satisfactory concordance was reached between the high yields of LA of 61.1 mol%, 67.7 mol% and 61.4 mol% calculated by the model, and the experimental yields of 60.5 ± 2.1 mol%, 65.2 ± 2.9 mol% and 61.5 ± 4.0 mol% (under optimum conditions of 190°C, 7.0% w/v of H 2 SO 4 , 75 min) for SCB, RH and SS, respectively. The biorefining of the agro-industrial wastes under optimum operating conditions allowed a satisfactory catalytic depolymerization of cellulose, regardless of the degree of crystallinity. The estimation of yields led to suggesting a strategy from the point of view of process synthesis and design, integrating SCB, RH and SS to supply their off-season and, thus, to ensure the supply of raw materials in the production of LA.

Levulinic acid (LA) is currently one of the most promising chemicals derived from biomass. However, its large-scale production is hampered by the challenges in biomass hydrolysis and the poor selectivity due to the formation of humins (HUs). This study addresses these challenges using the biorefinery concept of biomass fractionation. A three-step process (pretreatment, delignification, and acid-catalyzed conversion) was optimized to produce LA from SCB considering the yield (Y LA ), efficiency (E LA ), and concentration of LA (C LA ) as functions of temperature, reaction time, acid concentration, and solids loading. By means of a multi-response optimization, values of Y LA (20.9 ± 1.25 g/100g ISF-D ), E LA (37.5 ± 2.24 mol%), and C LA (25.1 ± 1.50 g/L) were obtained at 180°C, 75 min, 7.0% w/v H 2 SO 4 , and 12.0% w/v of solids loading. Six scenarios for production of LA were analyzed in terms of yields of LA, HUs, lignin, and other sugar-derived products considering one-, two-, or three-step processes. The economic analysis indicated that the three-step scenario delivers better economic figures given that other valuable biomass fractions (hemicellulosic sugars and lignin) are better used and contribute to the overall economic performance of the process. The results also demonstrate the burden of HUs in the economics of the process because it was shown that the largest production of LA is also linked to the largest formation of HUs, which does not necessarily yield the best economic results. These findings indicate the importance of added value by-products for the profitable production of LA in biorefineries.

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Ethanol production in Brazil started in the early 1930s due to laws created by the Brazilian government. However, ethanol production only increased significantly with the National Program of Ethanol implementation in 1975. This program was another action taken by the Brazilian government aiming to provide conditions for the development of the ethanol industry in the country. With the program, it was possible to achieve significant progress; however, it finished in the mid-1980s. Currently, ethanol is produced on a large scale by more than 300 sugarcane mills all over the country. In 2016, the Brazilian government provided another incentive for ethanol production by creating the RenovaBio Program, which aimed to reduce greenhouse gas emissions. Besides the environmental aspect, Brazil’s ethanol industry needs to develop to supply future biofuel demand. According to the forecast provided in this paper, and considering technical, economic, and environmental aspects regarding the Brazilian ethanol industry, the current and only feedstock used is likely to be insufficient. Thus, the ethanol produced from corn would be an attractive secondary feedstock to complement sugarcane ethanol as the primary feedstock.