Exergo-environmental evaluation of liquid biofuel production processes

The aim of this work is to evaluate some production processes of biomass-derived fuels by introducing an exergo-environmental indicator called the Renewability Performance Indicator (λ). This study clearly demonstrates that not all biofuel production processes are sustainable. According to this evaluation methodology, ethanol and sugar production from sugarcane, and ethanol production from amilaceous or lignocellulosic materials obtained from the banana plant cannot be considered as renewable processes, due mainly to the high exergy destruction, especially in chemical and biochemical reactions. On the other hand, biodiesel and kernel oil production from the fresh fruit bunches of the African oil palm can be considered as a renewable process as a consequence of the low exergy destruction, related to the exergy content of the products, in the oil extraction and transesterification processes. The Renewability Performance Indicator also suggests ways to improve the sustainability of biofuel production processes.