Comparison of two pelleting methods for cellulosic ethanol manufacturing: ultrasonic vibration-assisted pelleting vs. ring-die pelleting

Cellulosic ethanol made from cellulosic biomass is a sustainable alternative to petroleum-based liquid transportation fuels. One of the major challenges to cost effectiveness of cellulosic ethanol manufacturing is low density of raw cellulosic biomass that causes high costs of biomass transportation and storage. Pelleting can significantly increase biomass density,resulting in reducing the transportation and storage costs. Ring-die pelleting, a traditional pelleting method, generally involves high-temperature steam and high pressure, and often use binder materials. Ultrasonic vibration-assisted (UV-A) pelleting is a new pelleting method without using high-temperature steam, high pressure, and binder materials. This paper reports an experimental study to compare pellet quality (density and durability), sugar yield, temperature, energy consumption, microstructure of corn stover processed by UV-A pelleting and ring-die pelleting with two level of sieve size (3.2 and 9.5 mm). Results showed that pellets produced by UV-A pelleting had comparable density, durability, and sugar yield as those produced by ring-die pelleting. UV-A pelleting required higher energy consumption than ring-die pelleting and produced higher temperature than ring-die pelleting.