|
First-generation feedstock
|
| Starch and sucrose feedstocks |
High butanol yield |
Occupies potential crop land |
| Sufficient fermentable substrates through simple pretreatment processes |
Competes with food supply |
| Significantly increases the overall cost of fermentation |
| |
|
Second-generation feedstock
|
| Lignocellulose biomass |
Cost-effective, huge carbon resources |
Difficult to achieve sufficient fermentable sugars from complex and recalcitrant biomass |
| No competition with food supply |
Requires complex pretreatment and detoxification processes |
| |
|
Third-generation feedstock
|
| Algal biomass |
No competition with cultivation land and food supply |
Significantly increases the cost of downstream processes due to low production and productivity of butanol |
| Fewer or no lignin and fermentation inhibitors |
Difficult to obtain sufficient fermentable sugars |
| |
|
Fourth-generation feedstock
|
| Syngas |
Increased CO2 capture ability |
Still at its infancy as a technology |
| No complex pretreatment process needed |
Several unknown key parameters that limit butanol production |
| Directly utilises clostridia with a high production rate |
Poor mass transfer from gas to liquid |
