Comparison of energy performance and environmental impacts of three corn stover-based bioenergy pathways

Corn stover for bioenergy production has been in development because of its environmental benefits and displacement of conventional energy. This study compared, from cradle-to-grave life-cycle assessment (LCA) perspective, energy performance and environmental impacts among corn stover-based bioenergy pathways of production of electricity (CSE), bioethanol (CSB) and bio-natural gas (CSG) in China. The tool used was the eBalance model with a local database. The results indicated that no single conversion pathway simultaneously maximizes energy and environmental performance. The study showed that the CSE pathway exhibited the best energy performance (energy input/output = 39%), whereas the CSB pathway presented the best comprehensive environmental performance. The global warming potential (GWP) mitigation ranged from 0.50 kg CO2-eq to 149.39 kg CO2-eq per metric ton of fresh corn stover of 86% moisture for the three pathways. Assuming that half of the corn stover in China were used for the three bioenergy production pathways, the GWP mitigation would reach 42.38 million ton CO2-eq in 2020. A breakdown of environmental impacts indicated that contributions of sub-processes varied among the three pathways. The study suggested that electricity consumption for the CSB and CSG pathways and nitrogen utilization in cornfield for the CSE pathway should be decreased to reduce GWP in further corn stover-based bioenergy production according to a sensitivity analysis.