Burning fossil fuels is the main issue with CO2 emissions because that it adds CO2 into the atmosphere by releasing carbon that was sequestrated underground.
On the other hand, burning renewable plant matter is pretty much neutral: The plant absorbs carbon from the atmosphere while growing and that carbon is released back into the atmosphere when the plant is essentially burned to release energy.
The main problem with biofuels is that they may compete with other crops for land, etc. But if they are produced from plant waste that was already being produced anyway then they are a pretty good option.
On the other hand, burning renewable plant matter is pretty much neutral: The plant absorbs carbon from the atmosphere while growing and that carbon is released back into the atmosphere when the plant is essentially burned to release energy.
The main problem with biofuels is that they may compete with other crops for land, etc. But if they are produced from plant waste that was already being produced anyway then they are a pretty good option.