“the trees have absorbed CO2, so burning them is CO2 neutral” is correct as far as it goes, but it completely ignores externalities and second-order effects.

If you burn biofuels you encourage people to clear-fell forests to grow biofuels, as happens in Indonesia and Brazil.

If you promote burning biofuels, you divert attention from cleaner alternatives (Solar PV, wind).

If you make a big deal about biofuels, you create the impression that nothing really has to change.