November 29, 2001(revised on October 12, 2005)
Corn as a Non-Ethanol Heating Fuel Source
As a result of recent low corn prices and high propane prices, there has been increased
interest in the use of corn as a heating fuel. Corn burning stoves and furnaces have been available for many years.
Current technology has improved the efficiency of corn burning; hence, corn burners are becoming more economical.
Corn burning stoves and furnaces feed corn from a holding bin into a firepot where the corn is burned and a small
electric fan provides air for combustion. In general, corn-burning stoves heat one room. Corn burning furnaces
have the ability to heat an entire house by using a heat exchange system somewhat similar to gas furnaces.
Heat from alternatives
Heat available from a fuel source depends on the BTUs available from the fuel source and the heating systems efficiency. A BTU, or British thermal unit, is scientifically defined as the amount of energy needed to raise the temperature of one pound of water one degree Fahrenheit. The BTU is a nationally accepted standard of measuring the heat content of fuel.
BTUs produced from various sources are shown in Table 1. A bushel of shelled corn produces 352,800 BTUs. This compares to 91,500 BTUs from a gallon of propane. A bushel of corn has almost the same potential energy as four gallons of propane.
The number of BTUs actually produced into usable heat depends on the efficiency of the furnace. Today's gas and oil burning furnaces are all rated on a federally mandated efficiency standard. After mandated testing, each furnace is labeled with its Annual Fuel Utilization Efficiency, termed A.F.U.E. The higher the A.F.U.E., the more efficiently the furnace will heat your home. Since the early 1980's furnaces have been available with A.F.U.E. ratings ranging from approximately 80% to 98%, compared to older well-maintained furnaces with annual efficiencies of only 55% to 65%. A.F.U.E. ratings do not consider heat loss from ducts. Duct losses can range from near zero, for homes with ducts located within the heated space, to as high as 30% or more.
Geothermal heat pumps have seasonal efficiencies up to 300 percent. Heat pumps are able to provide efficiencies greater than 100% because heat pumps move heat, instead of releasing heat through a burning process as is done in furnaces and boilers. Electricity is used to run a heat pump's compressor motor. For every one unit of electricity that the motor uses, more than one unit of heat can be captured and moved by the refrigerant that is being pumped through the heat pump's coils.
Comparing operating costs from different heating sources
Heating costs per million BTUs can be calculated by knowing the price of the fuel, BTUs from the fuel, and the seasonal heating efficiency. The cost per million BTUs ($/MMBTU) equals:
(1,000,000 x price of fuel) / (BTUs per unit of fuel x system seasonal efficiency)
Costs for alternative heating sources are shown in Table 2. Fuel prices and BTUs used in the calculations are shown in Table 1.
For fuel prices shown in Table 1, burning corn in a shelled corn burner is relatively cost efficient. A shelled corn burner has an $8.10 cost per MMBTU. Only a geothermal heat pump has a lower cost. Burning propane in a 90 % AFUE furnace has a $20.89 cost per MMBTU. Thus the heating cost with a shelled corn burner is less than a 90 percent efficient propane furnace.
How well corn burning compares depends on fuel prices. Table 3 shows breakeven propane prices for various prices per bushel of corn. If corn were priced at $2.00 per bushel, then the equivalent price for propane used in a 90% AFUE furnace would be $0.67 per gallon. Or if you have an older type unmodified propane furnace with an estimated seasonal efficiency of 65%, you would need to be able to buy propane for only $.48 per gallon to get an amount of heat equal to $2.00 corn used at 70% seasonal efficiency.
Now using this information let's look at some estimated annual heating costs for a home. In central Illinois it would be reasonable for an 1800 square foot house to use 71,500,000 Btus (71.5 MMBtus) of heating energy during a typical heating season. The table below indicates various annual heating costs for this hypothetical home.
Costs for a typical home of 1,800 square feet that uses 71,500,00 BTUS of heating energy are shown in table 4. There are great variations in the cost of heating a home. Mainly the price of fuel and the seasonal efficiency of the heating system cause the cost difference.
At the annual fuel prices indicated above, operating costs for burning corn are less than many other heating sources. However, operating costs depend on fuel prices, which can vary considerably. Operating cost comparisons for burning corn are also favorable at a $2.40 per bushel, the average price of corn over the past twenty years.
This information does not consider the fixed costs associated with buying or maintaining a heating system. These costs will vary considerably across the alternatives. A complete analysis prior to switching heating sources and/or furnaces should include an examination of the costs of buying and maintaining complete heating systems, as well as the cost fuel.
Mr. Doug Carolus, Energy Use Manger, Illinois Power (Retired) and Paul Mariman, Unit Educator, University of Illinois Extension