Process-Level Sustainability and Resource-Efficiency Assessment of Corncob-Based Lactic-Acid Production using gPROMS

Abstract

This study evaluated the process-level sustainability and resource efficiency of an integrated corncob-to-lactic-acid process simulated in gPROMS. The steady-state pathway comprised dilute-acid pretreatment, enzymatic hydrolysis, fermentation, membrane filtration, acidification, purification and product storage. At a reference corncob throughput of 2,500 kg h⁻¹, the process produced 1,984 kg h⁻¹ lactic acid in approximately 2,002 kg h⁻¹ purified product. The process achieved 87.6% overall efficiency, 78.4% carbon-conversion efficiency, 96.8% lactic-acid recovery and 99.1 wt% product purity. Total heating demand was 2,678 kW, equivalent to 4.86 MJ kg⁻¹ lactic acid; the purification reboiler accounted for 43.5% of this demand. Direct process-water intensity was 6.05 L kg⁻¹ lactic acid. Filtration cake and gypsum were generated at 842 and 684 kg h⁻¹, giving a combined solid-residue intensity of 0.769 kg kg⁻¹ lactic acid. The estimated greenhouse-gas indicator was 1.42 kg CO₂-eq kg⁻¹ lactic acid within the adopted boundary. Purification heat, water use and solid-residue management were the principal hotspots. The results provide a process-development baseline for heat integration, water recycling, residue valorisation and subsequent cradle-to-gate assessment.