Biofuels

A biofuel is difficult to define. Most of the fossil fuels we use are biological in nature. Perhaps we have to say that a biofuel is one that does not add to the stock of total carbon dioxide in the atmosphere. These are plant forms that, typically, remove carbon dioxide from the atmosphere, and give up the same amount when burnt. Naturally, all the other fossil fuels have done the same, but we are talking about a time scale of one or two years for the biofuels, whereas the fossil fuels can only be considered on a time scale measured in millions of years.

The biofuels are therefore considered to be "CO2 neutral", not adding to the carbon dioxide level in the atmosphere. The type of biofuel used will depend on a number of factors, chief amongst them being the available feedstock and the energy that can be used locally.

Biodiesel

Biodiesel was probably the first of the alternative fuels to really become known to the public. The great advantage of biodiesel is that it can be used in existing vehicles with little or no adaptation necessary. Biodiesel is, naturally, a compromise for this reason, but still balances positively on the energy scales. There are energy plants available that will produce a higher yield in kWh per area, but the simplicity of having a fuel that is fully compatible with present fuel and engine technology makes it very attractive.

Cars running on BioEthanol, which is produced from agricultural crops, sugar cane or bio-mass, are governed by the same law of physics as those using gasoline. That means both emit CO2, as an inevitable consequence of the combustion process. But there is a crucial difference: burning ethanol, in effect, recycles the CO2 because it has already been removed from the atmosphere by photosynthesis during the natural growth process. In contrast, the use of gasoline or diesel injects into the atmosphere additional new quantities of CO2 which have lain fixed underground in oil deposits for millions of years.