Economic and environmental factors favor the adoption of lignocellulosic bioenery crops for ethanol production. However, lignocellulosic biomass is recalcitrant to saccharification, and this is, at least in part, due to the presence of the phenylpropanoid-derived cell wall polymer lignin. Analysis of alfalfa plants in which lignin content and composition had been modified through independently down-regulating each of six enzymes in the lignin pathway revealed that reduction in lignin content, but not altered lignin composition, increased sugar release from dried biomass by both acid pre-treatment (hot sulfuric acid) and digestion by a cellulase mixture. In both cases, the extent of sugar release was inversely proportional to lignin content. Acid pre-treatment could effectively be omitted in the processing of biomass with the lowest lignin levels. The gains in fermentable sugar production are discussed in relation to other phenotypic consequences of lignin modification.