Updates on softwood-to-ethanol process development.

Softwoods are generally considered to be one of the most difficult lignocellulosic feedstocks to hydrolyze to sugars for fermentation, primarily owing to the nature and amount of lignin. If the inhibitory effect of lignin can be significantly reduced, softwoods may become a more useful feedstock for the bioconversion processes. Moreover, strategies developed to reduce problems with softwood lignin may also provide a means to enhance the processing of other lignocellulosic substrates.

Effect of oxygen delignification operating parameters on downstream enzymatic hydrolysis of softwood substrates.

Enhanced oxygen delignification of softwood pulp samples (taken upstream and downstream of a commercial oxygen delignification unit) improved the initial rate of enzymatic saccharification and overall yield of monomeric sugars by 62-82% and 76-80%, respectively. Laboratory-scale experiments were used to examine the effect of a broad range of operating parameters (temperature, time, caustic concentration, and oxygen partial pressure) on the effectiveness of oxygen delignification. Using empirical models, kappa number (residual lignin content) was found to effectively predict final conversion to monomeric sugars.