Butanol is quite similar to gasoline and can be produced from biological waste. As such it might become an essential part in the future of the global energy mix.
Burning fossil fuels increases the amount of CO2 in our atmosphere, with serious consequences such as ocean acidification and an increased greenhouse effect. Reducing CO2 emission is important, though it would still leave much CO2 still in the atmosphere. Actually we should look for ways to remove that from the air, one way to do so would be reforesting.