What do we mean by Carbon Neutral? The CO2 produced in its combustion and fermentation will equal the CO2 used in its production.
Well, to make the ethanol a plant photosynthesizes to produce sugar.
6CO2 + 6H2O → C6H12O6 + 6O2
Sugar is then fermented to produced ethanol.
C6H12O6 → 2C2H5OH + 2CO2
When ethanol is combusted, the CO2 evolved equals the CO2 used in its production.
2C2H5OH + 6O2 → 4CO2 + 6H2O
It does look that way but when you dig deeper…
Well, what about the energy (and hence, CO2 produced) used to cut the sugar crop, make the fertilizers, power the machinery, light and heat the fermentation plant, etc.
The picture is suddenly not so ‘green’ as it makes out.