Are Biofuels carbon neutral?

I always wondered how can biofuels be carbon neutral while they emit CO2 just like non-renewable sources when they are burnt. I finally found an answer when reading a book on renewable energy today.

The concept is that biofuels come from biomass or plants which grow by accumulating resources from soil, CO2 from the atmosphere and sunlight from the sun. So what ever the quantity of CO2 emitted by burning biomass is just the CO2 that it has accumulated during its life time. Hence, by replanting the crops or trees at the same time when they are being burnt, we are just balancing the intake and emission. Thus Biofuels are cabon neutral = a green renewable resource.