Among various pretreatment methods, dilute acid pretreatment
has been most studied because it is highly effective and directly
end-hydrolyzes the hemicelluloses fraction (Yang and Wyman,
2008). However, dilute acid has several disadvantages. It often
leads to the production of side products that inhibit enzymatic
hydrolysis and fermentation and mitigating their effect often
requires extensive conditioning of the hydrolysate. This increases
sugar losses (Kumar and Murthy, 2011; Yang and Wyman, 2008).
Also, dilute acid pretreatment is an expensive process with high
capital costs for acquiring corrosion resistant reactors and high
operation costs for chemicals, neutralization and disposal (Yang