Life-cycle assessment-based comparison of different lignocellulosic ethanol production routes

Abstract

This work conducts a life-cycle assessment (LCA) of ethanol production from sugarcane bagasse in the Indian context. A cradle-to-gate system boundary was considered, and a functional unit of 1 MJ of energy from ethanol was used. Eight pre-treatment technologies and four hydrolysis-fermentation technologies were considered, thereby comparing 32 process combinations. Process data were collected from various published studies, government reports and also personal communication, and were used to perform LCA. The ReCiPe and TRACI models were used to perform the impact assessment using OpenLCA 1.6.1. The results show that the dilute acid pre-treatment (DA) with simultaneous saccharification and fermentation (SSCF) processing route had lower impacts in most categories. The global warming potential for this combination was 0.132 kg CO₂ eq. per MJ, with 85% of the contribution due to steam generation. The impact can be reduced to 0.019 kg CO₂ eq. per MJ by using a natural gas for steam generation. Ammonia fiber explosion (AFEX) pre-treatment had the highest impact in many categories, primarily due to ammonia production, implying the importance of ammonia recycling. DA had a lower impact due to higher yields and lower biomass requirements. The water footprint ranged between 232 and 672 L/L of ethanol and was mostly dominated by agricultural water.

Keywords:

• Life-cycle assessment
• ethanol
• India
• bagasse
• water footprint
• dilute acid pre-treatment

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to acknowledge the Department of Biotechnology (DBT), Government of India, for funding this research through grant BT/EB/PAN IIT/2012.