(516c) Substrate Dependency on the Effect of Pretreatment by Aqueous Ammonia

Pretreatment of corn stover by aqueous ammonia through ARP process has shown very promising results in terms of digestibility and overall sugar yield. This process achieves high level of lignin removal as well as high level of carbohydrate retention. However, when this process was applied to a different feedstock, hybrid poplar, the pretreatment results were quite different. The extent of delignifcation was somewhat lower, but the digestibility was far below that of corn stover. Study has also been made with two different batches of hybrid poplar having different sugar and lignin compositions. The effects of pretreatment on the composition of these two batches were similar, yet the digestibilities were significantly different. Lignin content is believed to be one of the major factors affecting the enzymatic digestibility. It appears that not only the gross lignin content but also the properties of lignin and how it is situated in the biomass structure play a role in the enzymatic digestion. To verify this, we have examined corn stover and hybrid poplar feedstocks treated under various ARP conditions by SEM, XRD, and FTIR. The results were organized into physical properties and surface characteristics. Correlations were sought between these factors and the digestibility with emphasis on isolated effect of lignin.