Lignocellulosic n-butanol co-production in an advanced biorefinery using mixed cultures

An advanced biorefinery design is proposed for co-producing n-butanol (butan-1-ol, CAS 71-63-3), acetone (propan-2-one, CAS 67-64-1) and ethanol (CAS 64-17-5) (ABE), as well as hydrogen (H2, CAS 4368-28-9) and biogas from lignocellulosic feedstock using mixed cultures. The biorefinery does not pretreat the feedstock and employs the hemicellulose (CAS 9034-32-6) and cellulose (CAS 9004-34-6) feedstock fractions for producing hydrogen and ABE in separate low-cost, low process-complexity fermentation stages. These reaction stages were designed based on the authors' own experimental data under Consolidated Bioprocessing (CBP) principles. The biorefinery design also includes a novel separation stage, electricity-steam cogeneration and heat integration. The technical feasibility of the proposed biorefinery is demonstrated through a parametric analysis of the total production costs (TPC) and energy efficiency with respect to feedstock price and biorefinery capacity. The feedstock price is proportional to its polysaccharides content as a way of assessing the impact of limited feedstock availability on TPC. The proposed CBP hydrogen and ABE fermentation technologies reduced fixed capital investment 7.7fold and 8.6fold for mid-size (1000 t d−1) and large (2000 t d−1) capacities. The end-use energy ratio achieved was between 2.14 and 2.24 for this interval capacity. Design and process conditions were identified to achieve similar TPCs (0.75 $ L−1 for 1000 t d−1 and 0.63 $ L−1 for 2000 t d−1, respectively) of sound conceptual designs previously published employing conventional technology. The results obtained in this study were compared with inflation-updated TPCs of conventional-technology biorefineries from works published over the past fifteen years, highlighting the advantages of the proposed design.