A Novel Process of Butyric Acid Production by Fermentation of Biomass: Toward a Sustainable Economic Evaluation

In this study, an economic evaluation of butyric acid (HBu) production from wheat straw (WS) was performed using two processes: separate hydrolysis, fermentation and recovery (SHFR) and simultaneous saccharification, fermentation and recovery (SSFR). Recovery of HBu from the fermentation broth was performed by adsorption onto XAD-4 resin, followed by extraction into methanol and subsequent separation of HBu from methanol through distillation. The analysis was conducted for a grass-rooted plant with a capacity of 40 × 103 MT·yr−1 (40 × 103 metric tons·year−1). The direct fixed capital (DFC) costs for the SHFR and SSFR processes were estimated at $80.00 × 106 and $43.33 × 106, respectively. The lower DFC cost for the SSFR process was due to the integration of wheat straw saccharification, fermentation and recovery into a single reactor. The annual operating costs for the SHFR and SSFR processes were $40.52 × 106 and $30.99 × 106, respectively. The profitability analysis indicated that HBu from WS using the SSFR process could be sold for $0.91·kg−1 compared to $2.51·kg−1 for HBu produced from corn. These estimates were based on a WS purchase price of $100·MT−1. The current selling price of petroleum-based HBu is $1.39·kg−1 to $2.27·kg−1.