A biorefinery based on the biomechanical configuration of the digestive system of a ruminant for ABE production: a consolidated bioprocessing approach

Ruminants are capable of transforming biomass into useful products; therefore, they can be considered as consolidated processing units. A conceptual design is presented for a biorefinery scheme, imitating a ruminant, under a consolidated bioprocessing (CBP) approach for ABE (acetone-butanol-ethanol) fermentation. The biorefinery was simulated by using SuperPro Designer® v8.5 software. Wheat straw (WS) was used as feedstock. A sensitivity analysis of the impact of the butanol output concentration of the ABE fermentation reactor on butanol total production cost (TPC) was made. Butanol concentrations (9, 15, and 19 g/L) and a hydraulic retention time (HRT) of 72 h were fixed on previous studies using specific species of Clostridium. Using the best scenario, a sensitive analysis of TPC was explored for different feedstock capacities of 400, 600, 800, 1000, 1400, 1800, and 2200 MT DB/day. The results showed a TPC of US$0.98/kg for the best-case scenario (2200 MT of WS/day; 19 g of butanol per L; HRT of 72 h), which is competitive with current gasoline prices in Mexico. The biorefinery produced all of its steam and electricity requirements by means of the co-production of the hydrogen and methane that were used in the co-generation stage, along with lignin. In addition, the production of butanol against electricity and its impact on the economy of the process was compared. Finally, by increasing the production of methane for the production of electricity, the economic parameters were negatively affected for all scenarios.