**3. Conclusions**

There are several pretreatment methods available for SCB; however, the final choice for the selection of pretreatment methods depends upon the effective delignification or hemicellulose removal, low sugar loss, time savings, being economic, and causing less environmental pollution. Each pretreatment method has its own advantages and disadvantages. Instead of performing the chemical pretreatment alone, it is good to combine the pretreatment with other physico-chemical pretreatment such as steam explosion in order to improve the sugar yield and increase the lignin removal from SCB. The combination of pretreatment is a promising method to improve enzymatic hydrolysis and ethanol production from SCB.
