Biomass can be processed and turned into bio-fuels that means:
a) bio-natural gas or
b) bio-oil
The bio-fuels can be used as mineral oil or gasoline as fuel
-    in thermoelectric plants to produce electricity
-    in internal combustion engines (cars, airplanes, ships, etc.)
    Burning bio-fuels produces CO2 just like the burning of common fossil fuels (oil, gas, coal, etc.). Though this CO2 is the same amount as the one that the plant by the process of photosynthesis blocked into its trunk and leaves while growing (and not CO2 blocked by plants thousands of years ago and stored in oil, coal and natural gas). Remember that in the process of photosynthesis, water and carbon dioxide react and produce hydrocarbons stored in plants. Theoretically, if we could plant as many trees and plants as those used for biomass and biofuels there would have be no harmful side effects for the environment.