What are the current processes used?
Currently, there are two common ways to go about this process of making ethanol from lignocellulosic biomass:
Since SSCF has increased ethanol yield and lower capital costs than SHF, it is more commonly used in current plants and labs.
However, it's not perfect. There are still some issues that have yet to be worked out.
Problems with SSCF:
• The optimum temperature of hydrolysis is different from the optimum temperature of fermentation
- This leads to reduced efficiency and low yields, since neither the enzyme nor the microbe is working to its
full potential
• Enzymes = HUGE cost
- The enzymes (cellulases, hemicellulases, etc.) must either be produced on site in a separate reactor or
purchased commercially, which raise the inputs costs of the SSCF plant, making it not commercially viable,
at least for now.
• Poor xylose fermentation
- The yeast used in SSCF demonstrated poor fermentation of C5 sugars, again leading to inefficiency and
reduced yield.