Rice straw, a waste from paddy processing, has several characteristics that make it a potential feedstock for fuel ethanol production. It has high cellulose and hemi — cellulose content that can be readily hydrolyzed into fermentable sugars. The chemical composition of feedstock has a major influence on the efficiency of bioenergy generation. The low feedstock quality of rice straw is primarily deter­mined by a high ash content (10-17%) compared to wheat straw (around 3%) and also high silica content in ash (SiO2 is 75% in rice and 55% in wheat) [205]. On the other hand, rice straw as feedstock has the advantage of having a relatively low total alkali content (Na2O and K2O typically comprise <15% of total ash), whereas wheat straw can typically have >25% alkali content in ash [12].

In terms of chemical composition, the straw predominantly contains cellulose (32-47%), hemicellulose (19-27%), and lignin (5-24%) [48, 116, 159, 204] as shown in Table 9.4. The pentoses are dominant in hemicellulose, in which xylose is the most important sugar (14.8-20.2%) [149].