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You are here: > News > Jan. 6, 2006

Corn Stoves: an Interim Technology on a Crumbling Foundation?

Though cleaner burning that wood, and currently using a lower-cost fuel, the corn stove should not be regarded as a permanent solution to dependence on foreign oil. Do short term savings on the heating bill entail increasing famine risk in the long term?

by Mary-Sue Haliburton
Pure Energy Systems News
Copyright © 2006

Corn Stove by Northern Tool & Equipment

A corn stove or corn furnace is a lot like any combustion-based heater known since man first learned to control fire: it burns stuff, and the space around it warms up due to the heat radiating from the flames. Although it's not rocket science, there have been a few technical advances applied to raise the efficiency.

Because the stove or furnace burns dry kernel corn, it needs a hopper to feed this coarsely granular material into its firebox at a gradual rate, as opposed to opening a door and dumping in a coal-scuttle load of particles.

You set up the stove with its hopper, pour in a supply of corn kernels, and let the thing feed itself gradually until it runs out -- or until you remember to re-fill the hopper. (Those bushels sitting in the garage don't walk to the hopper by themselves.) The relatively small hopper of the "Baby Countryside" model holds 40 pounds of corn kernels, somewhat less than one bushel. This is said to be enough to heat a home for 40 hours on a “low setting”, but only about half that time when the heat has to be turned up high. Other stoves and furnaces have much larger hoppers for longer periods of operation.

Old-Fashioned Heating Plus Modern Gizmos

Inside corn furnaces are high-efficiency heat-exchangers -- such as are used in gas-burning furnaces -- which extract all possible heat from the exhaust. (Ref.) The manufacturer of the Magnum T40 model claims that this reduces emissions to "less than one gram" though the website does not explain how long a period it takes to emit this one gram, or from how much fuel it is derived. The T40 model is capable of outputting from 5000 BTU to 40,000 BTU per hour, and if strategically placed, could heat about 1500 square feet of living space. This strategic location may present a problem in some houses, as the issue of vent pipe length has a bearing on safety.

Safety and Insurability

To facilitate unattended burning while enhancing safety, there have been modifications to the original wood stove idea. An electrically-powered blower forces air into a "carbureted" fire, controlling the input rate. The blower has a similar effect to using a bellows, or to “huffing and puffing” onto a fire with your built-in bellows, the lungs. This is to stimulate brighter, hotter flame. The firebox also has insulation and shielding to protect combustible walls and furniture located nearby. All of these stoves and furnaces are depicted with closed, fireproof glass doors.

At least you don't have to chop the corn or other types of fuel pellets, and you avoid having some of the mess of splinters, bits of bark and the odd bark beetle to sweep up around the fireplace. So your house stays somewhat cleaner than with an ordinary wood fireplace. And the pellets don't create the same level of creosote buildup that you get from burning wood, which requires frequent chimney cleaning to stay safe.

At least, this doesn’t happen if the corn stove is diligently maintained and monitored.

However, improperly-installed venting systems can lead to smoke damage in the house, especially if the horizontal pipes are too long. And if the electricity fails, and the fire burns through the auger to the hopper, extensive smoke damage can result. In one example, this happened while the occupants were away for two days. The pellets smouldered continuously while no fan was working to pull the smoke outside. Smoke damage was so extensive that the house had to be torn down.

Mother Earth News reported that there have been so many cases of smoke damage from pellet-burning stoves in Canada’s Maritime provinces that insurers started to balk at providing coverage for homes equipped with these systems. (Ref. [sidebar]) This sidebar article emphasizes that installing the vent sufficiently higher than the firebox can help the smoke escape even if the fan breaks down.

Just because they don’t need fuel input as often as wood stoves, this doesn’t mean that a corn stove can be installed and ignored. It does require maintenance, and daily attention to ensure that the auger does not become clogged, and that ash is removed when required, that the hopper has not run out of fuel, and that electrical devices are all working properly.

Built-in Grid Dependence

Note that any motorized blower requires significant amounts of electricity to operate, keeping the pellet-burning system grid-dependent. The Magnum brand "T40" adorns the old-fashioned corn/pellet-burner with modern gizmos: a “state-of-the art” controller, a built-in automatic igniter control, a thermostat capable six-position multiple-speed solid state control, and status-light indicators, presumably of the LED variety. Again, all of these require electricity.

The heat exchanger system, which is widely used in pellet-burning systems, greatly cools the exhaust. This means that unlike the old-fashioned stovepipe which had to be vertical so that the hot air and smoke would rise above the roof, the exhaust pipe from a corn-burning stove can go through the adjacent wall. However, without help from natural convection, this cooled-down exhaust has to be forced out by a fan.

As many experienced in the great ice storm of 1998, when the electricity was off, their fancy programmable, automatic, self-starting furnaces didn't work at all. Never mind that the gas line to the house was uninterrupted, nor that the tank of oil on the premises was filled last week. There was no way to open the thing and light it with a match. Unless you had either a simple, really old-fashioned wood-burning Franklin stove with no electronics, or a windmill feeding a bank of batteries, you were up a frozen creek without a paddle and had to go to public shelters.

So far I have not found a listing for a corn-stove that's set up to co-generate the electricity to operate its own electrical gauges or controls, let alone the blower / exhaust motors which require more power. Co-generation of at least sufficient capacity to power their own motors and electronics would be the minimum; if the stove is operating at higher output for a cold climate, it should be able to feed electricity to other appliances as well.

Apparently there’s room for innovation and for upgrading existing stoves, perhaps using thermo-voltaic technology. In an ideal world, devices would be designed that could be retrofitted onto the earlier stoves, as well as being factory-installed on new models.

Convenience with Chores

For some, such a set-up may arouse nostalgic memories of the cottage with its plain wood stove. The simple iron box stove or the round Quebec heater is capable of overheating a cottage, even in the dead of winter, with a single hardwood log, though without the emotional bonus of being able to watch the fire burn. The old type of open-fronted Franklin stove with its wire screen to stop sparks, though less efficient, warmed a large space with its friendly glow. And of course the top surface was available for cooking.

Despite all the conveniences listed above, and not having to chop wood, the owner of a modern corn-stove is not exempt from ordinary physical effort. Beyond the push-button controls, you will still have to fill the hopper with the weighty bushels of corn (56 lb per bushel) or other pellet-fuels. And you have to keep an eye on the ash levels use the access panels and rake to remove buildup.

The photograph on the Magnum site depicts a kettle atop its more modern unit. Along with such evocative pictures from the past comes a less rosy one: emptying the ash-box into the bin in the outhouse for use "down the hole". (That worked well; salted down with ash after each use, the manure pile in the outhouse never smelled, nor did it attract flies, and the result was a nice nutrient-rich pit into which to plant a tree later when it was time to move the structure to a new pit.) What do people do with the ash from burning corn, if they don't have an "outdoor convenience"?

Water Heating

A-Maize-Ing Heat® Boiler & Bin

Some companies offer corn-fired water heating. One design, the punster-named "A-Maize-Ing Heat®", includes a tankless coiled pipe inside the firebox for rapid heating of 2.5 gallons per minute for the household, in addition to heating the water jacket surrounding the firebox. This boiler has a 14-bushel bin, allowing it to operate a week or longer without refilling. But it does mean having a really big box taking up space in your basement. (Ref.)

Its electricity needs include both a blower and the motor controlling the auger that transfers corn from the bin to the boiler's firebox. It's also equipped with other electrically-governed features such as a pressure-release valve, an "aquastat relay" and a high limit switch. The manufacturer of the "A-Maize-Ing Heat®" units proudly states that their dual auger drive controls combustion well enough that their furnace and boiler are the first to be given an official safety rating from the Underwriters Laboratories (the coveted UL listing). (Ref.)

Energy Independence?

The Magnum company markets both corn/biomass stoves and furnaces, and wood-burning stoves and furnaces. Their promotional page for the Magnum 7500 points out that by investing in a Magnum 7500 Corn Furnace, the purchaser would be assured that 100% of their money actually stays in America, as opposed to being used to import fossil fuels. (Ref.) Reducing dependence on foreign oil is of interest to many people, and this cozy "home-grown" argument sounds appealing.

But it would be only to the extent that the farm producing the corn is not relying on foreign oil to power its tractors and harvesting machines, that this would be true at all levels. If the corn growers involved were to make their own bio-fuels, and reduce or eliminate dependence on petroleum-based fertilizers, then corn might qualify as a fully domestic product. The security of supply would then be as good as the rainfall and other climate-related factors (man-made or natural) allow.

Is Burning Corn Environmentally Clean?

The claims made for this type of stove include the notion that burning corn is cleaner than burning wood. One may politely point out that this is, after all, combustion, and where there's fire, there is going to be at least some smoke and CO2 released into the atmosphere.

Burning kernel corn is said to be 99% efficient. That is, there is one pound of ash left from 100 pounds of the fuel-corn, less than the amount of ash usually left from an equivalent quantity of wood. The "A-Maize-Ing Heat®" furnace and boiler feed the combustion chamber from the bottom, thus pushing the ash out the top and into the collector pan for easy emptying while allowing the fire to continue burning. (Ref.)

A corn-furnace model using a 2" diameter feeding augur can also burn other types of biomass fuel, as long as it's been pelletized in a small enough size and shape to fit through without jamming up the pipe. However, pellets are sometimes of uneven energy content depending on the materials from which they were made. Pellets also tend to pack down in the burner, requiring a strong draft from below to ignite and to keep them burning until used up as near to completely as possible.

Making pellets from wood slash, roadside saplings, and waste matter is energy-intensive. The material has to ground up into sawdust, and then forced through the same type of machinery as dog-kibble. The resulting pellets also must be thoroughly dried. However, wood pellets do burn more cleanly than unpelletized logs. Because pellets emit less than EPA's no-test cut-off level of 800kg of particulates/hr, they are exempted from the smoke-emission testing program forced on log-burning home heaters. (Ref.)

Debate Smoulders over Bio-Fuel Efficiency

However, corn does happen to be, not byproduct biomass, but a primary food crop that is being sent up in smoke. Given the high inputs to produce corn, which include use (and sometimes over-use and exhaustion) of agricultural land, along with dedicated equipment and fuel for seeding and harvesting, running irrigation pumps, transporting the crop to market, etc. one might well ask whether this is the best use of the land for growing it, as well as of the energy being consumed in its production.

The debate is ongoing. On the one hand, David Pimentel, professor of ecology and agriculture at Cornell University, argues that the use of biomass as fuel is not sustainable. His report mentions that it requires 29 percent more fossil fuel to produce the corn than would be obtained from using ethanol distilled from it. (Ref.)

On the other hand, various arguments are posted on the internet site in rebuttal. For example, one naming himself "skeptic" argues that Pimentel's statistics are unrealistic and outdated. In the Cornell study, farm equipment is counted as having only a 10-year lifespan which increases the cost per year. However, as this "ole farmboy" argues, farmers generally keep machinery going for years longer than that if they don't want to go bankrupt.

In another post, John Powers states: "Pimentel seems to think it takes 1000 Gallons of Fuel (Diesel, Anhydrous Ammonia, Gasoline) to farm 1 acre of corn. ... at $2 per gallon of diesel, a farmer would spend $2000 per acre to harvest $400 worth of corn. So per Pimentel, farmers lose $1600 per acre farmed. A large farm (2000 acres) would be losing $3,200,000 per year using Pimentels data."

And a third opponent argues, "... he assigns no energy credit to one of the co-products of ethanol - distillers grains. Distillers grains are a high protein, high value livestock feed. Please also consider the other comments in just how far off he is in modern day production costs on the farm! Last year we consumed less than 2% of the corn crop as food - I don't think ethanol is starving the world!"

The jury is still out. However, given that arable land is being lost from food production for various reasons, it should give pause for thought. (Ref.)

Food or Fuel: Should We Be Choosing Between Them?

There is another factor not mentioned in the debate yet. That is, the quality of all corn is not the same. Some is so low in nutrients that it may not be classifiable as food. In 1994, Leonard Ridzon -- a hard-headed and pragmatic farmer -- described the decline in soil fertility and more and more land being taken out of production as a result. Instead of dealing with the problem at its source, hybrids were unwisely created to produce greater “yield” from poor soil. The agri-scientists simply ignored the issue of food value in favour of quantity over quality. In contrast to the older open-pollinated corn varieties, when tested, the high-volume hybrids were found to be incapable of taking up trace minerals. Consistently and most notably they all failed to take up cobalt, which happens to be a key element in vitamin B12, and protects livestock from undulant fever and brucellosis. (Ref.)

As agriculture relied increasingly on high-volume hybrids, Ridzon stated, each year "there are millions of bushels of corn that remain unpriced because the product has no nutritional value. Some of it has less than 3% protein, which should be unheard of." (Ref.) Such corn cannot sustain life or productivity in farm animals, never mind keep humans healthy. It may as well be burned either directly or as ethanol. The need to dispose of this non-nutritious corn may be the reason that ethanol is being promoted as a fuel.

Since this book was published in 1994, and soil carbon levels have continued to decline (ref.), the nutritional content of such types of corn may be even lower today. Some soil is now so depleted, toxic and compacted that water cannot penetrate it, and food production is unlikely to succeed. How far will this decline continue before the prices of foodstuffs, including corn, start to rise in reflection of their actual cost, and the spectre of scarcity looms?

Soil exhaustion and loss of potential for food production should be counted in the cost of corn for fuel, while the planet’s population continues to rise. Food sufficiency is already at risk due to soil depletion, erosion, and desertification. The solution, according to Ridzon, was not to make hybrids able to produce nutrient-empty bushels, but to restore soil fertility by rebuilding the carbon and mineral balance, and -- equally important -- by removing the toxic chemicals from the food chain.

Since that soil-restoration solution is not being done, or not widely enough, we are still at risk as more farmland is likely to become unusable. Will that land now being used now to produce fuel-corn and industrial corn have to be turned to food production for a hungry world population? If that does occur, the availability of both non-food kernel corn as fuel, and of energy-intensive palletized wood and other materials may drop, and their prices would then rise, as per supply and demand.

As one internet denizen commented, “Something is terribly wrong when it is cheaper to burn food for heat!” (Ref.)

Toxic Agricultural Methods

Toxins are not just applied to the surface anymore, but are now intrinsic to most of the plants and their kernels. Note that in the U.S., rather than being under the Food and Drug Administration, under the Environmental Protection Agency, bT corn is regulated as a pesticide. This is due to the gene inserted from a bacterium Bacillus thuringiensis, which produces a chemical toxin that kills European corn borer insects.

Farmers are supposed to plant 20% non-bT corn as “refuge” for the insects. The principle behind this odd requirement is that there should be non-resistant insects in the population to breed with those that are developing resistance, and slow down their acquisition of that capability. But, being in a cost-price squeeze, farmers have been resorting to over-planting the engineered corn in hopes of a larger crop. Therefore, resistance is increasing in the insect population – thus defeating the purpose of the biotech product and shortening its marketplace life, to the dismay of the patent holders. (Ref.)

Failure of even the financial safety margins are only the tip of the iceberg. Independent researchers and scientists oppose the biotech juggernaut with exposés of suppressed studies and other abuses of financial clout. (Ref.) With too much of this pesticide-corn being produced, and ongoing marketplace resistance to having bT corn in the food chain, it may well end up in the hoppers of corn stoves.

How safe is toxic corn as a fuel? While professional incinerators exist which can neutralize toxins, what byproducts of pesticides are produced in fires at the lower temperatures that exist in these small burners? It is probable that the question has not even been asked, and that no studies have been done to determine whether any such toxin byproducts are released into the atmosphere.

Storage of Corn

Bin of corn furnace in garage with double capacity

How many degrees will this stove, burning this amount, actually raise the temperature of the home compared to the outdoor conditions? For every degree the temperature is raised, energy must be expended. The best cost savings would always be in the temperate zones, while farther north where the gap is wider, the amount of fuel that must be expended will rise accordingly. The lower the outdoor temperature, the more fuel would be needed. Therefore, the colder the climate, the more significant issues of storage space and delivery charges will become. Presumably the stove will have to burn corn full tilt if the temperatures regularly fall into the sub-zero Fahrenheit or minus 20 Celsius range.

Depending on your climate zone, anywhere from eighty to a couple of hundred bushels would be needed for the whole winter. Delivered at one time to minimize freight charges, this quantity may not cost that much compared to oil or gas, but you will have to factor in the property tax you pay on your indoor space required to store the corn or other pellets.

Because this kind of fuel must be kept completely dry, you cannot leave it outside in the snow like wood, and expect it to dry out enough to be usable in a few hours. Even in waterproof packaging, it could be at risk from damage caused by wind, abrasion, etc.

Keep it Dry

Because this kind of fuel must be kept completely dry, you cannot leave it outside in the snow like cordwood, and expect it to dry out enough to be usable in a few hours. Wood logs with about 20% water will still burn, and the home interior may be that dry in cold weather, meaning that the chopped wood can dry out enough to use in the ambient air.

However, the pellet manufacturer reduces the water content to about 5% (Ref.) Such a low humidity is achievable only in an industrial drying kiln, and is well below what is livable for the human occupants of a house, as well as putting the structure itself at risk of developing cracks and other damage.   For human health, 30% humidity is more comfortable, and at only 20% many experience respiratory problems and dry skin. (Refs.)

Shelled corn intended for burning must also be thoroughly dried.  Being seeds, the kernels could even sprout if they get wet and would be useless. Waterproof packaging for pellets or corn could be damaged by wind abrasion, accidental puncture, etc. and allow snow melt to seep into the contents. Therefore, since pellet fuel and dried fuel-corn kernels cannot be dried out again to factory specs in the indoor humidity conditions that are suitable for human occupation, it is vital that such fuels be kept indoors where there is no risk of water penetration.

The Thin Bottom Line

A report by Casey Research, Inc. from a business point of view suggests that the economics of burning corn for heat are favourable enough to allow people selling the corn stoves to make a profit. There seems to be a waiting line for as many as can be manufactured. (Ref.)

However, this article was generally painting a rosy picture of the cost savings. As one poster to a discussion form on this thread states, “I think folks buying corn stoves might a bit short sighted on the fuel cost,” and he suggests not to count on it “down the road” when costs may go up. (Ref.) Also, there are some projections that oil and gas prices will not continue to rise or stay at present levels, but will go back down, which would make a corn-burning stove as popular as an 8-track tape player. (Ref.)

At current pricing, the bottom line for homeowners is that, at the current prices for oil, buying corn to burn costs less than the fossil fuels, which appear to be on a permanent track toward higher.

This fuel is bulky, and heavy: each bushel weighing in at 56 lb. delivers about 8,000 BTU of energy per pound, or 448,000 per bushel. (Ref.) Many homes have room only for about forty or fifty bushels at a time, and so would require several trips by the delivery truck, with charges for fuel and time added on.

And it is a substantive investment. The furnaces and stoves are heavy cast or forged objects, with insulation and electrical devices. Capital costs are comparable to other types of furnaces. Where the difference is supposed to kick in is the price of pellet fuels. As long as this stays competitive, the cost of the furnace will be made back in fuel savings. Various publications have calculated costs for burning corn for those considering this investment, and these estimates are available online. (Ref.) It is a good idea to check prices in your region and currency, and to factor in transportation cost.

Are homeowners making decisions solely on the basis of myopic attention to the bottom line? Will the short term apparent benefits outweigh the issues of maintenance chores and long-term implications for the world food supply?

In keeping with the overall purpose of this website, which is to further the development of new technology that is not just “clean-burning” but at best not dependent on combustion at all as its basic principle, thinking twice before investing in a corn stove is recommended. If you do make a commitment to this technology, do the “homework” both up front in checking costs, and later in attentive maintenance, and enjoy being warm for the interim. Reduction of even the lower emissions from corn or pellets should still be a goal, to be accomplished with better insulation and other ways to prevent heat loss during winter.

# # #


(Links that require explanation.)

See also

Page posted by Sterling D. Allan Jan. 3, 2006
Last updated December 24, 2014





"It is harder to crack a prejudice than an atom." // "I'd rather be an optimist and a fool than a pessimist and right." -- Albert Einstein

ADVISORY: With any technology, you take a high risk to invest significant time or money unless (1) independent testing has thoroughly corroborated the technology, (2) the group involved has intellectual rights to the technology, and (3) the group has the ability to make a success of the endeavor.
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