ETHANOL FERMENTATION HEAT CALCULATOR
This Ethanol Fermentation Heat Calculator is based on fundamental principles of biochemical thermodynamics and metabolic energy balances. Here’s a breakdown of the science behind each step:
Fermentation Reaction and Energy Release:
The primary reaction for ethanol fermentation is:
C
6H
12O
6→2C
2H
5OH+2CO
2+heat
- Glucose (C₆H₁₂O₆) is metabolized by Saccharomyces cerevisiae (yeast) into ethanol (C₂H₅OH) and carbon dioxide (CO₂).
- This reaction is exothermic, meaning it releases heat.
- The enthalpy change (ΔH) for the breakdown of glucose into ethanol and CO₂ is approximately -234 kJ per mole of glucose.
In addition to ethanol and CO₂, yeast metabolism produces small amounts of glycerol, acetic acid, and yeast biomass.
Heat Release for Each Fermentation Product:
| Product |
Reaction Heat (ΔH, kJ/mol glucose) |
| Ethanol |
- 234.0 |
| Glycerol |
-165.0 |
| Acetic Acid |
-867.0 |
| Yeast |
-480.0 |
Molar Mass of Glucose and Conversion to Moles
Moles of glucose = Glucose Mass (g) / Molar Mass of Glucose (g/mol)
Heat Contribution from Each Product
Heat from Product=(Moles of Glucose)×(ΔHProduct)×(Yield Fraction)
Total Heat Released and Heat Per Gram of Glucose
Total Heat = ΔH Ethanol + ΔH Glycerol + ΔH Acetic Acid + ΔHYeast Biomass
Why Does the Heat Release Vary?
- Higher Ethanol Yield → More Heat Released: Ethanol production releases a moderate amount of heat.
- More Glycerol → Less Heat Output: Glycerol formation is less exothermic than ethanol production.
- More Acetic Acid → Very High Heat Output: Acetic acid formation is highly exothermic.
- More Biomass → More Heat Absorbed: Yeast biomass growth requires energy, reducing the net heat released.