Optimization of the hydrolysis of Agave tequilana bagasse and methane production from hydrolysates

The Agave tequilana bagasse is a lignocellulosic residue from the tequila industry that has great potential for biofuels production. Therefore, first part of this study aimed to optimize the conditions of acid hydrolysis for sugar recovery from two types of Agave tequilana bagasse, which were obtained from two different processes of tequila production, the traditional, in which the Agave tequilana heads are cooked, and the alternative, in which the Agave tequilana heads are uncooked. Meanwhile, second part of this work aimed to evaluate the feasibility of methane production in batch reactors from the acid hydrolysates under two conditions, with and without nutrient addition. Results showed that at optimal conditions for acid concentration, temperature and reaction time, the hydrolysis over the cooked bagasse was more effective for sugar recovery compared to the hydrolysis over the uncooked bagasse. Sugar concentrations in the cooked and uncooked bagasse hydrolysates were 27.9 g/L and 18.7 g/L, respectively. However, the presence of 5-hydroxymethylfurfural was detected in the cooked bagasse hydrolysate, and therefore, the uncooked bagasse hydrolysate was selected as a more suitable substrate for methane production. Interestingly, the anaerobic digestion results showed that the batch reactor operated without nutrient addition obtained a higher methane yield (0.26 L CH4/g COD) than the batch reactor operated with nutrient addition (0.18 L CH4/g COD), proving that it is feasible to produce methane from hydrolysates of Agave tequilana bagasse and suggesting that addition of nutrients is not needed when this type of substrate is used.