The Economic Feasibility of Producing Industrial Syrup from the Enzymatic Hydrolysis of Corn Stover Using Acidic Deep Eutectic Solvent

The Aspen Plus process simulation with techno-economic assessment was used to evaluate the industrial-scale feasibility of enzymatic hydrolysis of corn stover. Choline chloride (ChCl)-based deep eutectic solvents containing lactic acid (LA), formic acid (FA), and acetic acid (AA) as hydrogen bond donors were used to pretreat the corn stover. Optimal pretreatment conditions (140 °C and a solid-to-liquid ratio of 1:30) achieved high levels of lignin (77.3%, 72.9% and 73.5%) and xylan (90.2%, 93.5% and 90.5%) removal for ChCl/LA (1:5), ChCl/FA (1:5) and ChCl/AA (1:5), respectively, while retaining significant levels of glucan (81.3%, 76.2% and 82%). Subsequent enzymatic hydrolysis at 10% substrate loading yielded glucose at 93.7%, 91.2% and 82.7%, respectively. The DES pretreatment and solvent recovery units accounted for 41.9% of capital costs at a solid-to-liquid ratio of 1:30. Increasing the solid-to-liquid ratio to 1:10 reduced total capital investment by 41.6%. Operational costs were heavily influenced by DES solvent consumption (81.2–92.7% of raw material costs). Of the DESs, the ChCl/FA (1:5) pretreatment process offered the best economic performance, achieving a minimum selling price (MSP) of USD 988.2 per ton. Sensitivity analysis identified glucose yield as the most critical cost driver (±20% variation caused a ±25% change in the MSP, followed by DES recycling efficiency. Fluctuations in DES prices had a limited impact (±20% variation caused a change in MSP of only 2.4–3.8%) due to the solvent recycling mechanism. This study demonstrates the potential of DES pretreatment for industrial application through process optimization, solvent recycling and valorization of by-products.