Biomass combustion releases CO2 that was recently captured by growing plants — over a full growth-harvest-burn cycle the net addition to the atmosphere is close to zero, unlike fossil fuels.
Net efficiency = combustion efficiency × (1 - moisture penalty)
Moisture penalty: wet fuel wastes energy boiling off water before it burns
- Feedstock — wood chips, dedicated energy crops, or agricultural waste; each has a different baseline efficiency and moisture range.
- Moisture content — higher moisture lowers net energy yield since energy goes into evaporation first.
- Feed rate — how fast biomass is fed into the boiler.
Real-world relevance: this moisture penalty is exactly why biomass fuel is dried/pelletised before use in real power plants.