Uses: fuel, solvent, feedstock.

Principles of green chemistry must be applied to the process + modifications must be made if necessary.

PRO’s of fermentation

• In I/GCSE Chemistry, Renewable feedstock - e.g. waste plant material – maize, sugar cane.
• Un-fermented parts used as animal food
• 21st century = further development --> more parts CAN be fermented

• Agricultural waste / sludge can be fermented

CON’s of fermentation

• Lots of land needed

• May need the space for human foods

• Some parts can’t be fermented

Reaction

Opt. Temp: 30 degrees

• Too high --> denatured enzymes
• Too low --> Rate of Reaction too slow b/c enzymes working slow

Opt. pH: pH4

• Changes in pH --> breaks bonds within / between enzymes --> changes shape --> less effective b/c denatured
• Prevent oxygen b/c it converts ethanol to ethanoic acid, which in turn lowers the pH.

Limited conc. of ethanol is produced (14/15%) b/c if the ethanol production is any higher, the yeast gets killed and the fermentation gets stopped.

Distillation – separating chemicals based on boiling points

• In I/GCSE Chemistry, This is used to obtain higher conc. of ethanol.

Is fermentation sustainable?

Analyse the data and think about:

• Raw materials e.g. renewable feedstock
• Atom economy --> waste = low AE
• Waste --> released? Recycled?
• Energy costs e.g. for opt. temp.
• Environment e.g. GHG
• Health + safety
• Profit
• Benefits / risks

Energy balance - Energy output needs to be greater than energy input

• In I/GCSE Chemistry, Higher EB = greener process.
• Different feedstock release different EB

You got it now!