io energy is primarily derived from the burning of plant material to generate heat that is then used directly, or to produce electricity. Such "biomass" can be derived from wood, garbage, landfill gases, bagasse, agriculture crops/waste, forest residue, sewage, etc.
Some of the processes that are used to convert biomass into energy include combustion (ex. burning wood), gasification (ex. combustible gas mixture- syngas), pyrolysis (ex. charcoal), anaerobic digestion (ex. methane), and fermentation (ex. ethanol).