Phosphoric acid-acetone process for cleaner production of acetone, butanol, and ethanol from waste cotton fibers

To move biobutanol toward a commercialized biofuel, its production process should be developed based on renewable and cost-effective carbon sources. In this study, it was shown that cotton, a commodity that typically ends in landfill sites or incinerators, can be utilized as a feasible source after the phosphoric acid-acetone process. The treatment with phosphoric acid (19 g/g) resulted in 94% cotton dissolution after 60 min, and the addition of acetone (41 g/g) was accompanied by 97% precipitation. Enzymatic hydrolysis of regenerated cellulose (15 filter paper unit per mL (FPU/mL)) followed by fermentation by Clostridium acetobutylicum resulted in 5.4 g/L acetone-butanol-ethanol (ABE). In this process, 208 g acid and 138 FPU cellulase were used for production of each g ABE. Increasing enzyme dosage to 25 FPU/g resulted in 79% higher butanol production (161 g ABE/kg). Through cyclic acid re-concentration, phosphoric acid consumption decreased to 82 g/g ABE. Furthermore, by applying an additional dilute phosphoric acid pretreatment, the enzyme consumption reduced to 113 FPU/g ABE. (C) 2018 Elsevier Ltd. All rights reserved.