Throwing the log in a landfill (or building a house with it) would accomplish the same thing, and is a heluva lot cheaper.
The fact is, there is ample demand for high density energy storage. People want to go places, people want stuff brought to them. Until battery technology makes a massive leap into the realm of eating roses and shitting rainbows, combustible fuels are the only economically feasible option.
In that realm, our options are A) keep digging up fossil fuels, then burning producing a bunch of C02, or B) capturing a bunch of C02, turning it into biofuel, then burning it to release the same amount of C02.
Put in simple math terms:
Fossil fuels: net CO2 = CO2 from energy to extract + CO2 from burning
Biofuels: net C02 = CO2 from energy to extract + (CO2 from burning - CO2 from growing)
= CO2 from energy to extractAre you saying biofuels are not only ineffective at reducing CO2 emissions, but impractical as well?