Methods |
Features and Advantages |
Disadvantages |
Sodium hydroxide (NaOH) |
remove lignin, low temperature and pressure, |
inhibitory, long pretreatment time, expensive chemical, complex recovery process |
Lime |
the least expensive alkali; safe to handle; can be simply recovered |
inhibitory, long residence time, neutralization or washing process required |
Ammonia fiber expansion (AFEX) |
low enzyme requirement, minimized degradation products, high solids loadings |
formation of oligomeric form of hemicellulose degradation products
|
Ammonia recycle percolation (ARP) |
high efficiency for delignification, |
low solids loadings |
Hot-water |
low cost, less inhibition, low corrosion, less residues, high simplicity |
high temperature, particle size reduction required to obtain high yield |
Dilute sulfuric acid |
high yield |
inhibitory, causticity reagent, acid neutralization required |
SO2-catalyzed steam explosion |
high solids loadings, rapid penetration of biomass |
highly toxic, inhibitory |
Concentrated acid hydrolysis |
high yield |
slow rate of conversion, acid recovery systems required |
Ionic liquid |
effective at solvating cellulose, minimal environmental impact |
high cost, induction of cellulase inactivation; effective regeneration; causticity and toxicity of ILs; selection of stable ILs |
Lewis acid |
lower corrosion to equipment, lower enzyme demands |
overall efficiency needs to be improved, the effect of Lewis acid residues on the downstream processing need to be evaluated |
