Techno-economic Analysis and Life Cycle Assessment of a Corn Cob-based Biorefinery

Transforming agricultural residues into value-added chemicals drives the sustainable development of a biobased economy. The acetosolv process was investigated for the fractionation of corn cobs into cellulose, hemicellulose, and lignin fractions, integrating experimental work with process simulation, techno-economic analysis (TEA), and life cycle assessment (LCA). Laboratory-scale experiments using 70 vol % acetic acid and 30 vol % water, catalyzed with sulfuric acid, yielded 48.2 ± 1.9 wt % cellulose and 15.1 ± 1.2 wt % lignin, with a solvent recovery of 96.0 ± 1.5 vol %. Gas chromatography analysis indicated the formation of ethyl acetate as a byproduct from the reaction between acetic acid and ethanol, used as a washing solvent. The acetosolv process was simulated using Aspen Plus software, assuming a corn cob processing capacity of 150 ktons/y and market prices for the three product fractions (cellulose, hemicellulose, and lignin). The formation of these fractions in the acetosolv reactor along with the downstream separation of acetic acid, ethanol, and ethyl acetate was modeled. TEA results predict that the process could operate profitably based on the assumed market prices for cellulose, hemicellulose, and lignin. Both capital and operating costs are dominated by unit operations associated with solvent handling and recovery. Sensitivity analysis indicated that process profitability was preserved when considering experimentally observed variance in the yields of the three fractions. Valorization of the cellulose, hemicellulose, and lignin fractions would thus increase profit margins. LCA predicted a climate change impact of 0.22 kg CO2-eq/kg feedstock, which is in the range reported for organosolv processes. The acetosolv fractions and renewable products made from them have the potential to generate carbon credits, which could reduce the overall carbon footprint of the corn ethanol industry.