The idea behind biomass is that it's fuel that can be cultivated and harvested. Be it wood, corn, soya beans, palm or cane, or whatever, you grow "fuel". You burn it, and then you burn each year a new harvest.
The best thing about it is that any CO2 released by its burning is CO2 which was absorbed by it during the previous year rather than millions of years ago so the net release of CO2 into the atmosphere is zero.
EDIT: Just noticed you already wrote words to that effect in a previous post!