Bioalcohols are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches, or cellulose. Biobutanol is also known as biogasoline as claimed to provide a direct replacement for gasoline, because it can be used directly in a gasoline engine. Ethanol can be used in petrol engines as a replacement for gasoline; it can be mixed with gasoline to any percentage. Most existing car petrol engines can run on blends of up to 15% bioethanol with petroleum/gasoline. Ethanol has a smaller energy density than does gasoline; this fact means that it takes more fuel (volume and mass) to produce the same amount of work. An advantage of ethanol is that it has a higher octane rating than ethanol-free gasoline available at roadside gas stations which allows an increase of an engine’s compression ratio for increased thermal efficiency.
Methanol is currently produced from natural gas, a non-renewable fossil fuel. It can also be produced from biomass as biomethanol. The methanol economy is an alternative to the hydrogen economy, compared to today’s hydrogen production from natural gas.