Biomass Energy Output Calculator
Biomass fuel energy output depends on the type of fuel, its moisture content, and the combustion efficiency of the heating system. The EIA publishes standard heat content values for biomass fuels in the Monthly Energy Review. This calculator estimates gross energy content (BTU), useful heat output (BTU and kWh) after accounting for moisture and combustion efficiency, and compares the cost per MMBtu with natural gas and electricity.
Biomass energy calculation formulas
Gross Energy (MMBtu) = Quantity (tons) x Heat Content (MMBtu/ton) x (1 - MC/100)
Useful Heat (MMBtu) = Gross Energy x (Combustion Efficiency / 100)
Useful kWh = Useful MMBtu x 293.07 [1 MMBtu = 293.07 kWh]
Cost per MMBtu = (Total Fuel Cost) / Useful Heat (MMBtu)
Heat content values from EIA Monthly Energy Review, Appendix A (Table A4). The factor 293.07 kWh/MMBtu is derived from 1 BTU = 0.00029307 kWh (NIST standard). Moisture content correction: wet fuel contains less burnable carbon per ton, so gross energy is reduced proportionally.
Biomass vs fossil fuel cost comparison
- Natural gas: approximately $12-15/MMBtu useful heat at $1.20-1.50/therm and 95% furnace efficiency.
- Heating oil: approximately $20-30/MMBtu useful heat at $3-4/gallon and 85% boiler efficiency (1 gallon = 138,500 BTU).
- Wood pellets: approximately $15-25/MMBtu useful heat at $250-350/ton and 75-85% pellet stove efficiency.
- Dry cordwood: approximately $10-20/MMBtu useful heat depending on regional prices and equipment efficiency.
Biomass energy output: frequently asked questions
What are the EIA energy content values for common biomass fuels?
The EIA Monthly Energy Review (Appendix A) publishes heat content for biomass fuels: wood and wood waste (dry): approximately 17.0 MMBtu/ton (air-dried at 20% moisture: approximately 14.0 MMBtu/ton); wood pellets: approximately 16.4 MMBtu/ton; corn (grain): approximately 15.0 MMBtu/ton; switchgrass (dry): approximately 16.5 MMBtu/ton; corn stover: approximately 16.0 MMBtu/ton.
What is moisture content and how does it affect energy output?
Moisture content (MC) is the weight of water as a percentage of total weight. Wet-basis MC = (water weight / total weight) x 100. Every percent of moisture reduces the available energy output because energy is used to evaporate water. A log at 50% MC (wet-basis) has roughly half the usable energy of the same wood fully dried. DOE recommends below 20% MC for efficient combustion.
What combustion efficiency should I assume for biomass?
Combustion efficiency varies by technology. EPA-certified wood stoves and pellet stoves achieve 70-90% efficiency. Industrial biomass boilers achieve 70-85% efficiency. Older non-certified wood stoves may be only 60-70% efficient. The EPA Method 28 test procedure defines how efficiency is measured for wood heaters.
How is biomass energy converted from BTU to kWh?
1 kWh = 3,412 BTU. To convert BTU to kWh, divide by 3,412. This EIA standard conversion is used to compare biomass with other energy sources. For electricity generation from biomass, you must also account for the thermal-to-electric efficiency of the generator (typically 20-35% for steam turbines).
Is biomass considered a renewable energy source?
The EIA classifies biomass as a renewable energy source. However, the carbon cycle implications depend on the source and time horizon. The EPA and DOE frameworks generally treat sustainably managed forest biomass as carbon-neutral over a rotation period, but this is an area of ongoing scientific and policy debate. The EPA's Clean Air Act framework addresses biomass emissions at 40 CFR Part 60.
Official sources
- U.S. EIA Monthly Energy Review: Appendix A - British Thermal Unit Conversion Factors (Table A4, Biomass).
- U.S. DOE Office of Energy Efficiency: Biomass Basics (DOE EERE).
- EPA: Wood Burning Efficiency and Air Pollution (EPA BurnWise).
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.