In I/GCSE Chemistry, we will learn about the production of ethanol 2B.
Uses: fuel, solvent, feedstock.
Principles of green chemistry must be applied to the process + modifications must be made if necessary.
Fermentation
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
In I/GCSE Chemistry, Cellulose polymers from feedstock are heated with acid to break it down into simple sugars.
Optimum conditions
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
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 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!
