Chemical Composition of Native and Ammonia Fiber Expansion Pretreated Rice Straw-Unextracted versus Extractives-free Material

Characterization of chemical composition for lignocellulosic biomasss (LCB) is essential in the conversion process of LCB to bioenergy and biochemicals. Accurate quantification of chemical composition allows for better determination of the LCB conversion and product yield in LCB processing. However, the presence of the extractable material is stated to strongly influence the compositional analysis of the LCB. This study was conducted to analyze and compare the chemical composition of (A) native-whole unextracted rice straw of (1) untreated rice straw (URS) and (2) AFEX pretreated rice straw (AC1RS and AC2RS) as well as (B) the extractives-free rice straw of (1) URS and (2) AFEX pretreated rice straw (AC1RS and AC2RS). The effect of the AFEX pretreatment on the composition of rice straw was determined using the extractives-free material of URS, AC1RS and AC2RS. The actual reported composition of native-whole rice straw of URS and AFEX pretreated rice straw were made based on the corrected values of the extractives-free rice straw of URS and AFEX pretreated rice straw. The rice straw was analyzed for structural constituents such as glucan, xylan, arabinan and Klason lignin as well as non-structural constituents. The results demonstrated that the extractives in native-whole unextracted rice straw significantly interfere with the analysis of Klason lignin. The lignin content of the rice straw was overestimated if the extractives were not removed prior to the compositional analysis. The extractives in rice straw statistically did not affect the carbohydrate analyses. However, some soluble sugars were removed from the rice straw during the extraction process.