A Multi-Level Analysis Approach to Measuring Variations in Biomass Recalcitrance of Douglas Fir Tree Samples

Abstract

Biomass recalcitrance is a major bottleneck in the development of an economically viable process to convert woody biomass into fuels and other valuable chemicals. Selective breeding of trees with low recalcitrance toward biofuel conversion could help significantly reduce the cost of biofuel production, but such efforts would require a greater understanding of the nature of variations in the biomass recalcitrance of softwood species. The complexity of biomass recalcitrance, however, hinders research into determining the viability of breeding programs aimed to improve the recalcitrance of softwoods. In this study, a method was developed to determine biomass recalcitrance at three levels: chemical composition, pretreatment yield, and sugar release from the enzymatic hydrolysis. This method is designed to investigate the biomass recalcitrance variations among different families of Douglas-fir, which is the most abundant and promising softwood species for biofuel production in the Pacific Northwest region. Wood samples from 150 plantation-grown trees were collected and analyzed to test the method and the applicability of the parameters screened. The relationships between these levels are discussed to determine the best method for screening large D. fir populations. A parameter, a biomass recalcitrance factor, was introduced to quantify the level of biomass recalcitrance toward sugar production from different D. fir trees.