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?
Pure Energy Systems News
Copyright © 2006
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
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
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
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
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
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
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"?
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.)
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
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
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
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
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
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
# # #
(Links that require explanation.)
- p. 36 of The
Carbon Cycle, by Leonard Ridzon with Charles Walters, AcresUSA,
1994. ISBN 0-911311-46-7
Carbon Cycle, p. 38
The journal Nature,
Sept. 8, 2005, and originally also described at: http://www.alertnet.org/thenews/newsdesk/L05384446.htm
this link is no longer online.] "Global warming causes soil to
release carbon -study" - Global
warming is causing soil to release huge amounts of carbon, making efforts to
fight global warming tougher than previously thought, scientists said on
Wednesday. (by Peter Graff; Reuters; Sept. 7, 2005)
"Corn Stoves Wildly
Research 2004 report;week of December 20, 2005. (Third article on page.)
Feb. 1, 2004
article from USAToday
explains that respiratory discomfort begins below 30% humidity. See
also, Why indoor air
dries out in winter, graphic (not all heating systems dry the air, only
the inefficient ones; some require a de-humidifier to avoid risk of rot and
fungus growing in damp wood or plaster). And Independent
analysts explain indoor humidity issues, also http://www.kiva.net/~daylight/humidifier.html
(This one includes a chart relating indoor humidity to outdoor temperature
indicating levels which are safe for the house)
Do a search on “corn
stove operating costs” to look for the newest figures. Also, the Mother
Earth News article cited before has data. Manufacturers such as http://www.hrgcornfurnaces.com/corn_compare.htm
offer their own figures as well.
Page posted by Sterling
D. Allan Jan. 3, 2006
Last updated December 24, 2014