Mild dilute sulfuric acid (DA) and Sulfite Pretreatment to Overcome Recalcitrance of Ligno- celluloses (SPORL) pretreatments were directly applied to wood chips to save energy in wood size reduction [18]. Enzymatic hydro- lysis and simultaneous enzymatic saccharification and fermenta- tion (SSF) using commercial enzymes and a conventional Saccharomyces cerevisiae were conducted using the pretreated solid fraction after disk milling. All process energy and yield data were recorded. Wood recalcitrance was quantitatively determined based on saccharification conversion and process energy data. The over- arching goal of the study was to provide objective and practical bioconversion information to researchers, landowners, and policy makers for the production of poplars as a bioenergy crop.