초록
Biological production of second generation biofuels such as biohydrogen (H<SUB>2</SUB>) or methane (CH<SUB>4</SUB>) represents a promising alternative to fossils fuels. Alkaline pretreatments of lignocellulosic biomass are known to enhance the accessibility and the bioconversion of hollocelluloses during anaerobic digestion and dark fermentation processes. In the present study, four different configurations were investigated: one-stage CH<SUB>4 continuous</SUB> and two-stage H<SUB>2 batch</SUB>/CH<SUB>4 continuous</SUB> process with and without alkaline pretreatment of sunflower stalks (55<SUP>o</SUP>C, 24h, 4g NaOH/100g TS). The results showed that two stage H<SUB>2</SUB>/CH<SUB>4</SUB> (150+/-3.5mL CH<SUB>4</SUB>g<SUP>-1</SUP> VS) did not improve methane yields compared to one stage CH<SUB>4</SUB> (152+/-4mL CH<SUB>4</SUB>g<SUP>-1</SUP> VS). Although alkaline pretreatment was shown to be inefficient in improving the H<SUB>2</SUB> yields in the two-stage H<SUB>2</SUB>/CH<SUB>4</SUB> process, an increase in methane yields by 26% and 29% were observed with one-stage CH<SUB>4</SUB> and two-stage H<SUB>2</SUB>/CH<SUB>4</SUB> production compared to one-stage CH<SUB>4</SUB> process without alkaline pretreatment, respectively. Chemical analysis of the solid digestate showed that hemicelluloses were the most preferred substrates compared to cellulose whereas lignin remained undegraded in all four studied configurations. Finally, energy balance showed that a positive energy balance and economic sustainability can be achieved when the alkaline pretreatment is applied at a high substrate concentration and/or when heat is recovered at a maximum efficiency during the pretreatment step.