Alkaline pretreatment to enhance one-stage CH4 and two-stage H2/CH4 production from sunflower stalks: Mass, energy and economical balances

Abstract Biological production of second generation biofuels such as biohydrogen (H2) or methane (CH4) 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 CH4 continuous and two-stage H2 batch/CH4 continuous process with and without alkaline pretreatment of sunflower stalks (55 °C, 24 h, 4 g NaOH/100 g TS). The results showed that two stage H2/CH4 (150 ± 3.5 mL CH4 g−1 VS) did not improve methane yields compared to one stag…