Burning Shelled Corn

Burning shelled corn as a fuel can be a feasible way of dealing with the high prices of conventional fuels.
Burning Shelled Corn - Articles
Burning Shelled Corn

Burning shelled corn as a fuel can be a feasible way of dealing with the high prices of more conventional fuels such as fuel oil, propane, natural gas, coal, and firewood. Using corn as a fuel does not compete with the food supply needed for nourishment throughout the world. While it is recognized that malnutrition is a serious global problem, the world is not experiencing a food production problem. Instead, the world faces political challenges associated with providing infrastructure systems for food distribution and storage.

Contemporary agricultural systems can produce sufficient quality and quantity of food for the world's population, with additional resources available so that agricultural products can be used as fuel, pharmaceuticals, and chemical feedstocks. Shelled corn is a fuel that can be produced within 180 days, compared to the millennia needed to produce fossil fuels.

Corn Energy Equivalents

This table provides a method of calculating how much shelled corn would be required to replace the fuel currently being used for heating.

The corn energy equivalent table below provides an efficient way to calculate how much corn would be required to replace the fuel currently being used. For example, if a person uses 2 tons of hard coal per heating season, then about 6,720 pounds of shelled corn (2 x 3,360) will be needed to obtain the same heating value. Likewise, a person using 400 gallons of #2 fuel oil would need to use about 8,800 pounds of shelled corn (400 x 22) for the equivalent amount of heat.

Fuel Currently UsedPounds of Shelled Corn
1 ton of hard coal3,360
1 gallon of #2 fuel oil22
1,000,000 BTUs of natural gas170
1 gallon of propane15
1 full cord of firewood2,800
1 ton of wood pellets2,575
1,000 kWh of electricity635

Disposal of Corn Ash

A plan for proper disposal of corn ash needs to be developed before purchasing a corn-burning stove or boiler.

Burning shelled corn yields less ash residue than burning firewood or cinders from burning coal.

Corn ash has some modest value as a fertilizer and as a liming agent, with no evidence of heavy metals or any other contaminants. The corn ash (after cooling) can be safely applied to garden areas, flower beds, lawns, and fields.

Heat Energy Content of Shelled Corn

The combustion energy content of shelled corn is a critical factor in making energy comparisons of fuels. The energy content of shelled corn is not a constant value because of biological variability and management factors. Generally, the energy content of corn is in the range of 8,000 to 8,500 BTUs per pound of dry matter.

A BTU (British Thermal Unit) is a unit measure of energy. One BTU is the amount of heat energy needed to heat one pound of water one degree Fahrenheit. The factors that may influence the energy content of corn include variety of corn, soil fertility, weather conditions during growing season and at harvest, stage of maturity at harvest, drying method, and storage conditions.

It needs to be emphasized that the energy content of shelled corn is in the range of 8,000 to 8,500 BTUs per pound of dry matter based on bomb calorimeter studies.

The term "dry matter" refers to material that is "bone dry." The standard moisture content of shelled corn is 15.5 percent moisture on a wet basis. This means that each pound of shelled corn will actually consist of 0.845 pound of dry matter and 0.155 pound of water. Using a median energy content value of 8,250 BTUs per pound of dry matter, the energy content of one pound of shelled corn at 15.5 percent moisture is then 6,971 BTUs (8,250 BTUs per pound dry matter x 0.845). The figure of 6,970 BTUs per pound is referred to as the higher heating value (HHV).

The HHV needs to be further reduced because of the energy required to vaporize the 0.155 pound of water in the shelled corn since this energy is unavailable for heating purposes. The energy needed to evaporate the water is approximately 163 BTUs (1,050 BTUs per pound water x 0.155 pound). The net available energy content of a pound of shelled corn with a moisture content of 15.5 percent is then 6,810 BTUs. This value of 6,810 BTUs per pound of shelled corn is known as the lower heating value (LHV), a reduction of nearly 17.5 percent when the moisture content is taken into account. The actual energy content of shelled corn would be even lower if pieces of cob, husk, or stalks are mixed in with the shelled corn.

The tradition in the United States is to compare the thermal energy content of various fuels on the basis of HHV, whereas in Europe the standard practice is to use the LHV. In the Energy Selectors on this Web site, the energy content for shelled corn is assumed to be of 6,970 BTUs per pound of shelled corn for all the analysis, along with an assumed overall seasonal thermal efficiency of 75 percent.

Whenever reviewing commercial literature, be especially cautious of the recommendations and conclusions if the analyses are based on an energy content of the corn higher than 7,500 BTUs per pound of shelled corn and/or an overall thermal efficiency of 80 percent or higher.

Unfortunately, some manufacturers of corn stoves use the energy content figures of 8,000 to 8,500 BTUs per pound as though these figures were the energy content of the actual shelled corn itself. They frequently multiply energy content by the number of pounds in a bushel (56 pounds) and then report an energy content of 448,000 to 476,000 BTUs per bushel of shelled corn.

Figures as high as 10,000 BTUs per pound or 560,000 BTUs per bushel have been used in some analyses. Whenever these exaggerated energy contents are used in any analysis, considerable distortion will occur in the results.

Locating a Supplier of Shelled Corn

Do not purchase a corn-burning stove without first identifying a reliable supplier of shelled corn.

To find suppliers of shelled corn, contact the feed and seed stores in your area as well as any feed mills and grain elevators. The extension office in your county or the land-grant university in your state may also be able to identify suppliers of shelled corn.

If you know any farmers, contact them directly to inquire if they or other farmers they know will sell shelled corn to you on a direct basis. Be sure that the moisture content of the shelled corn that you buy is no higher than 15.5 percent for good combustion characteristics and for safe storage of the corn (see Quality of Shelled Corn).

Generally, it will be cheaper to buy the corn directly from a farmer than from a feed mill or elevator. Probably the most expensive place to buy shelled corn is from a fireplace/hearth shop where the corn is sold in cute little decorated bags. In many cases, it will be necessary to purchase a large amount of corn at a time to get the cheapest price for the corn. You may find it is necessary to purchase 25 bushels (1,400 pounds) to 100 bushels (5,600 pounds) to negotiate the cheapest price. Whenever discussing price, be sure to consider the cost for the delivering the corn to your home.

The price of corn fluctuates throughout regions of the United States and throughout each year. It is impossible for any supplier to provide a firm price for corn over an extended period of time, unless you buy the corn on a futures contract. You may be able to negotiate a price that is a fixed number of cents higher than the price of corn on the commodity market at the time of your purchase.

Quality of Shelled Corn

For best results, the quality of shelled corn to be burned in a corn-burning stove or boiler must be specified.

Moisture Content

The moisture content of the shelled corn should be no higher than 15.5 percent. Higher moisture contents will result in the growth of mold and mildew in the corn, thereby leading to spoilage of the corn. The growth of fungi will likely create problems of the corn clumping together in the storage area and the corn may not feed properly through the distribution system into the combustion chamber of the stove or boiler. The fungal spores may also cause or aggravate respiratory problems in people exposed to the spores.

Whenever the moisture content of the corn is above 15.5 percent, less heat will be available from each pound of shelled corn. For each 1 percent increase in moisture content above 15.5 percent, a corresponding reduction of about 90 BTUs of heat per pound of shelled corn will result.

Some models of corn-burning stoves and boilers may require that the moisture content of the shelled corn be as low as 13 percent to get efficient combustion of the corn. Be sure to ask the dealer or manufacturer about the recommended moisture content of shelled corn for efficient combustion.

Cleanliness

The shelled corn needs to be clean, with a minimum of broken kernels and foreign materials (cob pieces, husks, stalks, stones, and other residue). Small pieces of corn kernels may interfere with proper combustion and will likely cause some smoking problems. The foreign materials tend to clog the flow of the shelled corn into the stove's combustion chamber. Specify U.S. grade #2 to get the shelled corn with just a small amount of broken corn and foreign materials (BCFM). If there are problems associated with burning grade #2, then it may be necessary to specify U.S. grade #1, which will have even fewer BCFM. However, grade #1 corn will be considerably more expensive than grade #2.

Shopping for a Corn-Burning Stove?

As you consider purchasing a corn-burning stove or boiler, you will undoubtedly have many questions. Below you will find questions that are designed to help you gather the necessary information for making an informed decision.

The answers to these questions may vary from model to model and also depend on personal preferences and the anticipated location and function of the stove. However, satisfactory answers to all questions should be received from the dealer before committing to a purchase.

  1. Does the corn-burning stove have UL or CSA certification on the testing label?
  2. Does the operator's manual for the stove state that 100 percent shelled corn can be burned, or must the corn be mixed with wood pellets for good combustion?
  3. Can any other fuels be burned in the corn-burning stove? If so, what adjustments or stove modifications are required to burn some other fuel?
  4. How often will the supply hopper need to be filled when the stove is burning at full capacity?
  5. What are the maintenance requirements of the corn-burning stove compared to other stoves? How often do clinkers need to be knocked loose and removed? Must an additive (such as oyster shells) be burned along with the corn to ease the cleaning requirements?
  6. Are sugars from burning corn likely to accumulate in the combustion chamber? If so, what is the recommended way to remove the sugars?
  7. Where can shelled corn be purchased in this area? Be sure to have a plan for storing the shelled corn you purchase for the heating season and perhaps beyond (see Storage Requirements of Shelled Corn).
  8. What is the recommended moisture content of the shelled corn in order to get good fuel combustion?
  9. What type of exhaust ventilation system must be provided for the corn-burning stove? What are the local code requirements and insurance requirements for handling the combustion exhaust?
  10. What size corn-burning stove is needed for the intended application? Is the house layout appropriate for the convective movement of the heated air throughout the whole house? You need to decide if the stove is intended to be the primary heat source for the building or if it is intended to serve as a supplementary or back-up source.
  11. Can the corn-burning stove be connected with an existing hot-water or hot-air distribution system?
  12. How much experience does the dealer have with installing and servicing corn-burning stoves and boilers?
  13. Which stove models are intended for residential applications and which models are for commercial and industrial applications?
  14. What warranty comes with the stove? Under what conditions will the warranty be voided?

Storage Requirements of Shelled Corn

Proper storage of shelled corn is important for good performance of a corn-burning stove or boiler.

The corn must be stored in a clean, dry environment. It should not be stored directly in contact with a concrete or dirt floor. If the corn is in bags, the bags should be stacked on a pallet in an area free of rodents, birds, squirrels, and other varmints. If the corn is stored in bulk containers, the containers should not sealed shut because air must be allowed to circulate around and through the corn. Inspect the corn from time to time to ensure that there are no insect or disease infestations and that the corn does not develop a musty odor.

Shelled corn is generally sold by the bushel or by weight. One bushel of shelled corn with a moisture content of 15.5 percent weighs 56 pounds and requires a storage volume of 1.25 cubic feet. One hundred pounds of shelled corn (about 1.8 bushels) requires a storage volume of 2.25 cubic feet.

Authors

Bioenergy Biomass Energy Systems Thermochemical Conversion Energy Efficiency Controlled Environment Agriculture Solar Energy Resource Evaluation

More by Daniel Ciolkosz, P.E.