Ethanol can be produced by fermentation of sugar solutions using yeast. Ethanol can also be produced by a different method. Describe the process of fermentation and explain why ethanol produced by fermentation is considered a renewable fuel.

Fermentation is an anaerobic process in which glucose is broken down by yeast.
1. Yeast cells act as the catalyst, converting glucose into ethanol and carbon dioxide.
2. The overall reaction is:
C6H12O6 → 2 C2H5OH + 2 CO2.
3. The glucose used comes from plant sugars, which are renewable because plants continually produce them via photosynthesis.
4. When the ethanol is later burned, the CO2 released was originally fixed from atmospheric CO2 by the plants, making the fuel effectively carbon‑neutral.
5. Therefore, fermentation produces a renewable fuel that does not increase atmospheric CO2 levels.