There's two types of people in the world, those that understand maths and those that don't. Those that don't tend to think biofuels will save us and those that do, don't.
Ok we'll run some very simple calculations just to get an idea of just how much biofuel we'd need to replace the fossil fuels we're using in our vehicle fleets. To do this we'll make a few assumptions (I probably could look it all up but ballpark "guesstimates" should give us a reasonable estimate), we'll assume an average fuel consumption of 10l/100km, 20 000km of use per vehicle per year and 10 million vehicles in Australia and we'll treat it as all fossil fuels being replaced with ethanol just for sake of convenience, we're also assuming the same fuel economy from ethanol as from the fossil fuels (which it isn't, ethanol gives less km/l). So:
Fuel used per vehicle = 10/100 x 20 000 which is 2000l/yr
Now one tonne of grain makes about 650 litres of ethanol so 2000/650 gives just over 3 tonne of grain per vehicle to run for the full year which means we'd need to convert around 30 million tonnes of grain to biofuels per year, which unfortunatelly is roughly what we grow per year. In 2006-07 grain production dropped to below 20 million tonnes meaning we'd probably have to dip into the 5 million tonnes of sugar we produce per year.
So do you want to eat or drive?