Wood is the most widely available and least expensive biomass fuel available. Firewood is normally sold in units called cords. A cord of wood is a neat stack measuring four feet wide by four feet high and eight feet long. The heat content of a cord will vary depending on the species of wood. A cord of mixed softwood will have a heat value of 17 or 18 million BTU and a cord of mixed hardwood will have a heat value of 27 to 29 million BTU. By way of comparison a gallon of No. 2 fuel oil has a heat value of 140,000 BTU per gallon and propane has 93,000 BTU per gallon. Please use our fuel cost comparison tool to calculate the relative fuel costs in your area.
Corn is a fuel that is widely available in many parts of the country and can be used in the Multi-Heat boiler. Corn can be purchased in bulk or by the bushel (56 lb bags).
The energy content of corn isn’t constant, but approximately 20 lbs of corn is equal to a gallon of fuel oil. On average, the energy content of corn is between 8,000 to 8,500 BTU/lb of dry matter. One BTU (British Thermal Unit) is the amount of energy needed to heat one pound of water to one degree Fahrenheit. To get the net dry BTU rating on corn, one needs to factor in the moisture content. Average moisture content for corn is 12-15%. This gives corn an average BTU rating of 6,800 BTU/lb.
Because of the high demand for corn from the ethanol industry, corn has fallen out of favor as a fuel in recent years. Unless you are growing and drying your own corn, this may not be an economical fuel option for you at this time.
Wood Pellet fuel is manufactured from milled wood particles including waste wood and, less commonly, bark, which are pressed through dies at very high pressure.
Wood Pellets can be purchased in bulk or in 20 or 40 lb bags. The energy content of pellets is more constant than corn because of lower moisture content (4-8%). As a rough approximation, 17.5 lbs of wood pellets provide the same amount of heat as a gallon of heating oil. With these characteristics, wood pellets burn very efficiently. They are also very easy and safe to transport and store. Wood pellets have an average net BTU rating of 8,200 BTU/lb.