|
| Pretreatment | Advantages | Disadvantages |
|
| Physical | | |
| Milling, chipping, shredding, grinding, irradiation, and pyrolysis | Increase in biomass surface area & pore size, no requirement of chemicals, and depolymerization & reduced cellulose crystallinity | Highly energy intensive & industrially inapplicable as individual methods |
|
| Chemical | | |
Dilute acid pretreatment
Concentrated acid pretreatment | Lesser acid is needed
Efficient, low temperature required | Corrosive & formation of
fermentation inhibitors (furfurals) |
| Alkali pretreatment | Lesser inhibitors formation | Less effective for lignin-rich biomass |
|
| Physicochemical | | |
Steam explosion
AFEX (Ammonia Fiber Explosion) Method
SO2 and CO2 explosion | Lesser retention time
No inhibitors formation, can process coarse biomass
More effective than AFEX | Xylan & lignin degradation
Less effective for lignin-rich biomass
Unaltered lignin & hemicellulose |
| Liquid Hot Water (Aquasolv) | No catalyst required | High water requirement |
| Wet oxidation | Rapid | Fermentation inhibitors |
| Ozonolysis | No inhibitors formation | Very expensive |
| Organosolv | Pure lignin extraction | Costly & solvent inhibition |
| Oxidative delignification | Rapid, low temperature needed | Solvent recycling needed |
| Ionic liquids | High biomass loading processing | Solvent recovery required |
|
| Biological | | |
| Using lignolytic (white, soft and brown rot) fungi and actinomycetes | No inhibitors generation, no chemical or harsh conditions required, and low energy requirements | Very slow rate, at experimental stage |
|
