Integrated life cycle and techno-economic assessment of rice straw-based bioethanol production in India with on-site enzyme integration

Abstract

Open-field burning of rice straw remains a major environmental challenge in India, highlighting the need for sustainable residue management pathways. This study presents an integrated life cycle assessment (LCA) and techno-economic analysis (TEA) of rice straw-based bioethanol production under Indian conditions, using experimentally derived process data. The system includes alkaline pretreatment, on-site crude enzyme production, enzymatic hydrolysis, fermentation, and ethanol recovery within a cradle-to-gate boundary. A key distinction of this work is the explicit inclusion of on-site enzyme production as an internal process step. Here, rice straw-based ethanol production exhibited life-cycle GHG emissions of 2.90 kg CO 2 -eq L −1 , and the minimum ethanol selling price was estimated at ₹81.6 L -1 . Results indicate that pretreatment chemicals and biomass transport dominate greenhouse gas emissions, with pretreatment alone contributing 1.16 kg CO 2 -eq L-1 (38.5%). Feedstock procurement and pretreatment are the main cost drivers, accounting for 67% of the MESP. On-site enzyme production contributes only marginally to both emissions and costs. Internal use of lignin residues for process heat further improves system performance. Overall, the results suggest that rice straw-based ethanol could serve as a complementary pathway to support residue valorisation and emission mitigation, subject to the assumptions and scale-up limitations of this study.