Increasing Efficiency of Fuel Ethanol Production from Lignocellulosic Biomass by Process Integration

The conversion of lignocellulosic biomass to ethanol is currently one of the most popular options for sustainable production of transportation fuel from renewable resources. Due to the resistance of lignin compounds to biological degradation and the important heat requirements for distillation, conventional process designs for the combined production of ethanol and power are yet limited to a modest total energy efficiency of 50% to 55%. This paper investigates how to overcome this limitation by thermochemically converting the residues in order to increase the total energy yield by a combined generation of several fuels and power. Comparing a conventional design with different technological alternatives for thermochemical processing and heat and power recovery, the paper shows that the fuel yield can be more than doubled to reach total energy and exergy efficiencies of up 72% and 78%, respectively. From a methodological point of view, the paper demonstrates that the combination of process integration and exergy recovery techniques in a site-scale approach is key for tapping the full potential of the limited biogenic resources in future biorefineries.