|
| Pretreatment method | Advantages | Disadvantages |
|
| Alkali | (i) Efficient removal of lignin | (i) High cost of alkaline catalyst |
| (ii) Low inhibitor formation | (ii) Alteration of lignin structure |
|
| Acid | (i) High glucose yield | (i) High costs of acids and need for recovery |
| (ii) Solubilizes hemicellulose | (ii) High costs of corrosive resistant equipment |
| (iii) Formation of inhibitors |
|
| Green solvents | (i) Lignin and hemicellulose hydrolysis | (i) High solvent costs |
| (ii) Ability to dissolve high loadings of different biomass types | (ii) Need for solvent recovery and recycle |
| (iii) Mild processing conditions (low temperatures) | |
|
| Steam | (i) Cost effective | (i) Partial hemicellulose degradation |
| (ii) Lignin transformation and hemicellulose solubilization | (ii) Acid catalyst needed to make process efficient with high lignin content material |
| (iii) High yield of glucose and hemicellulose in two-step process | (iii) Toxic compound generation |
|
| LHW | (i) Separation of nearly pure hemicellulose from rest of feedstock | (i) High energy/water input |
| (ii) No need for catalyst | (ii) Solid mass left over will need to be dealt with (cellulose/lignin) |
| (iii) Hydrolysis of hemicellulose | |
|
| AFEX | (i) High effectiveness for herbaceous material and low lignin content biomass | (i) Recycling of ammonia is needed |
| (ii) Cellulose becomes more accessible | (ii) Less effective process with increasing lignin content |
| (iii) Causes inactivity between lignin and enzymes | (iii) Alters lignin structure |
| (iv) Low formation of inhibitors | (iv) High cost of ammonia |
|
| ARP | (i) Removes majority of lignin | (i) High energy costs and liquid loading |
| (ii) High cellulose content after pretreatment | |
| (iii) Herbaceous materials are most affected | |
|
| Supercritical fluid | (i) Low degradation of sugars | (i) High pressure requirements |
| (ii) Cost effective | (ii) Lignin and hemicelluloses unaffected |
| (iii) Increases cellulose accessible area | |
|
