One of the biggest challenges for using lignocellulosic biomass to generate biofuels is the pretreatment process, which involves the breakdown of the plant cell wall structure to release cellulose and hemicellulose from lignin. The structural mechanisms of lignocellulose breakdown during pretreatment are not yet understood. Poplar, especially hybrid varieties, has a lot of potential for biomass conversion because of its fast growing nature and the ability to regenerate from roots and trunks. The main goal of this research is to compare the effects of pretreating poplar wood using two different devices: 1) Accelerated Solvent Extraction (ASE) system (Micro-bench scale); and 2) Parr reactor (Bench scale) at various solid loading rates. Results of pretreatment experiments indicated that sugar yields did not change significantly when the solid loading concentration was increased, using a solvent saver mode with the ASE. It was also observed that sugars released during pretreatment increased as the pretreatment temperatures were increased from 170°C to 200°C. Fermentation and enzymatic degradation experiments carried out with these pretreated materials will be used to determine the pretreatment conditions that lead to maximum alcohol yield. Pretreatment conditions at laboratory-scale that mimic pilot-scale conditions to give similar yields will be identified. These results will be useful in developing process models for the pretreatment of poplar wood, in order to obtain high sugar and subsequently high biofuel yields. Results of nanoscale imaging, transport property studies and compositional analyses of the plant cell wall can be correlated with results of pretreatment and degradation experiments to better understand the breakdown mechanisms during pretreatment.