anyone ever burn "cob" corn in their Garn?

[topofthehil]

just wondering if anyone has ever burned cob corn in their Garn?
if so, how does the burn compare to ... say red oak?
I am thinking that if I ever get laid up again that my wife can load cob corn a lot easier than a 30" chunk of wood.
thanks for your input.

 

[Jim K in PA]

Never have myself, but am curious also. I posed this question over on the GARN forums and got a great response from Larry at Dectra: (broken link removed to http://garn.com/forums/p/28/246.aspx#246)

Short answer - it is much cheaper, at this point in time, to burn wood than corn. Unless you are growing it yourself, and have no other need or market for it, it's not worth the amount of work. The Btu content of dried corn on the cob is good, about 7k/lb., but the lb/volume ratio is not. It takes a lot of corn to get the heat, so you will be loading it more frequently, and for longer periods of time, to get the same heat as good quality wood.

And as Larry pointed out, you could grow and sell the corn, then use that $$ to buy cordwood already cut/split/delivered.

I may still try it someday, especially after corn prices crash.

 

[topofthehil]

thanks for the link Jim.
I am having trouble with my password on the Garn site, but I was able to use the link to get in.
the post got me to thinking why I and other farmers don't grow and harvest more cob corn if we can sell it for $8/bu.
there are some problems with the calculations in the example they gave.
for one, depending on quantity and where you buy the corn, shelled corn can be bought for around $3.50- $4.50/bu.
I am still looking for pricing for cob corn, but it will be several dollars less, as it is usually air dried in cribs and thus, has no drying costs.
so, the figure of $8/bu for cob corn that they used for their calculation is way too high.
also, the ideal (normal) moisture content of a bushel of shelled corn is 15.5%.
at that %, a bu of shelled corn weighs 56 lbs.
it takes a harvest weight of 68.4 lbs of ear corn to equal 56 lbs (1 bu) of shelled corn at 15.5% moisture.
they used the figure of 70 lbs, so that is close.
per the calculation of cob corn at 25% moisture weighing 35 lbs/bu, why would anyone pay $8 for a bu of cob corn when they can buy a bu of shelled 15% moisture corn weighing 56 lbs for less than half of that?
with this $8 I can buy two bushels of shelled corn, which is almost twice the weight, for the same cost .. that does not make sense to me.
maybe I'm missing something?
also, there was mention of a moisture content of 75% for cob corn in it's "un-dried" state.
seventy five percent moisture would be approxmately 28 days after "silking".
no one would pick corn at this stage. the kernels are still in their "milky" stage (R3) and just starting the dough stage (R4).
It takes another month to reach the maturity stage (R6).
corn is usually harvested when the grain is around the 20% to 30% moisture content range.
I would like to know where he got his data from. do you know?
I.E. a bu of cob corn @ 25% moisture weighs 35 lbs. that's good information.
I would like to know what a bu of cob weighs @ 15%.
I need to have a price for cob corn to have a more precise calculation.
also, I am not sure at what moisture content the cob corn is best for burning.
I will keep looking for more information.
sorry to go off on the moisture content tangent.

 

[DaveBP]

my wife can load cob corn a lot easier than a 30” chunk of wood.

How about a 15" chunk of wood?

 

[Jim K in PA]

TOTH - I have no idea where Larry got his #s from, and I did not have any other reference point to compare to. Your #s sound a lot more realistic to me, but with the craziness in the commodities markets this year, I really had no clue where things were.

So, if a bu of corn at ~15% MC weighs 56 lbs, you will get about an hour's worth of burn per bu (392k btu). A WHS2000 has in input rating of ~425k, which I and others see daily in real world conditions. I generally get about 1.5-2 hrs/load of cordwood, so with corn you will load more frequently, as I thought.

~15% MC is about perfect, as that is the MC that yields the highest output from cordwood. I doubt that it matters that it's corn rather than wood, but I would love to experiment. The corn on the cob will have more surface area/volume, so I would expect it to burn hotter, and faster. Higher MC helps control the rate of burn, so perhaps a higher MC would actually be beneficial (to a point).

Around here all the farmers use every bit of their corn for feed, so finding cob corn for sale is rare.

DaveBP's comment is also on point. I have found that 20" lengths is just about right, and splits in the 3-6" range are plenty big enough. I am not sure how small your wife is, but my wife is 5'-2" on a good day, and she has no problem loading and running the GARN. Niether do my 14 or 16 year old sons, but they are almost bigger than me now :gulp: .

 

[topofthehil]

I got some more information on the cob corn from my local extension agent. he says that a bushel is not always the same volume. A bushel of ear corn contains 56 pounds of shelled corn plus the cob.
that's where the 70 lbs come from. (56 lbs shell + 14 lbs cob)
a bushel of ear corn is considerably larger in volume (2.5 cubic feet) than a bushel of shelled corn (1.25 cubic feet). They figured this for sale purposes many years ago.
so, in the example that they gave of the Garn site is some what correct. a bu of shelled corn (1.25 cubic feet)is equal in cost to a bu of cob corn (2.5 cubic feet) less the cost of "shelling".
however, I would think that there would be more BTU's in the bu of cob corn as there is the shell and the cob that produces heat.

• 1 bushel ear (cob) corn = 70 lbs, 2.5 cubic feet (15.5% moisture)

• 1 bushel shelled corn = 56 lbs, 1.25 cubic feet (15.5% moisture)

• 1 cubic foot = 1/2.50 = .4 bushel of ear corn

• 1 cubic foot = 1/1.25 = .8 bushel of shelled corn

at this time, I am burning standing dried elm.
it burns great. I prefer the trees that are 10" and under in dia.
I just did not have time last year to cut and split enough oak to take me through this year.
I cut my fire wood to 30" lengths.
if it's over 8" in dia, I split it ... by hand.
I need to build a splitter.
the chunks get heavy for my wife.
I agree with you and others on burning smaller sticks. the hotter and faster the burn, the better.
maybe I should be splitting the wood if it's over 6" in dia, but my arms would be hanging down around my ankles after a couple of elm blocks.
I found that 28" - 30" lengths of 4" - 6" dia works best for me.
I need to figure out why I can't get into my Garn site account.
thanks for your input.

 

[SE Iowa]

I grow corn/soybean and alfalfa hay in Iowa. In todays world, a bushel is a measure of weight not volume. A bushel of corn weighs 56lbs at 15%MC. Soybeans weigh 60lbs/bushel at 12% MC. I think oats are 32lbs/bushel at ?%MC (its been a long time since I sold oats). In the old days they did not have scales all over so they went by volume. The problem is a thing called test weights. It is similar to wood in that some are more dense and weigh more per volume. One time I had corn that tested 64.5lbs/volumeteric bushel. This is highly valued by the elevators for hog feed (more calories/volume) and cost less to store, etc. At any rate, I found that the calculations from that post where quite a bit off, but I do agree with is general hypothesis. You could look at the following example to see if growing your own corn would be worth it.

Lets say you planted (or had planted by someone else) corn on one acre. Here in Iowa on average soils we would plant near 30,000 seeds per acre and would expect a final stand of 28,000 plants. On a reasonable year you could expect to yeild 180-200 bushels per acre which ould be about 0.4lbs of shelled corn per plant. The old times said that an average year would yield 0.5lbs/ear of corn which would be about right. If there were 28000 half pound ears of corn at 15% MC that would be 14000lbs total weigh @ 7,000 btu's per pound equaling 98,000,000 btu's per acre. I think a cord of good wood is between 25-30 million btu's. So it would be roughly 3 cords of wood per acre.

BUT; Unless you have a mechanical ear picker, husking 28,000 ears of corn would be more work in my opinion than cuting 3 cords of wood. Not to mention that dead wood is virtually "free" minus the chainsaw and oil/gas. Secondly, to raise that acre of corn cost about $700 when you factor in all the cost (although if doing it on you own land with small equipment/ manual labor, the cost would be significantly lower). Actual input cost are probably around $300 acre. But you have to look at opportunity cost to grow. You could sell the corn for $700 and buy cord wood.

My take; Corn is too expensive right now to burn. If you get laid up I think it would be more work for your wife to try to raise corn than get wood. If corn gets cheaper though, then it would probably be all right.

 

[topofthehil]

SE Iowa,
I think your figures are more realistic than those on the Garn site.
I was not going to switch to cob corn, but only use it in an emergency situation.
I lease some of my land out to a neighbor who does small scale farming ... four row planter, two row picker ...ect, so there is low overhead costs.
my plan was to exchange some land for his ear corn.
I did not know what ear corn was worth, so I asked the UW extension agent and he said to use a volume as a unit of measure for cost. that is, you would need 2.5 cubic feet of ear corn to equal 1.25 cubic feet of shelled corn.
or, if you have 70 lbs of cob corn that should be worth 56 lbs of shelled @ 15.5% moisture.
does this sound right to you?
thanks for your input.
I wish I could get 180 - 200 bu/acre.
I get around 150 in a good year.

 

[SE Iowa]

Yes, 2.5 cu ft does sound right. I think it is an excellent idea that you have. I often think about some outside the box ideas. For example I have a 7.5 and 4.5 acre patch of cropland that is 6 miles away from the rest of my land but within 1/2 of a mile from my house. I've thought about doing just what you are thinking about except I was going to raise black sunflower seeds. Then I could either sell them into Iowa City area (think Univ of Iowa educated type-local farming groups) as locally produced bird seed OR I could purchase these new small scale oil seed presses, and convert the oil into diesel fuel for the rest of my farm and feed the mash to my chickens. There would be some work and loss due to inefficiencies but part of it is I'm just to bullheaded to let "the man" get the best of me.

The other thing to consider is that corn may not stay at $3.5/bu. It could go to $6 or it could go back down to $2. This is a good thing for you! If corn stays cheap then burn it. If it goes up, sell it to someone who grinds corn for their cattle and buy some wood. This sort of hedges you against multiple scenario. I am quite jealous of your GARN but it is on my 5 year radar. Good luck.

 

[SE Iowa]

By the way, 180 to 200 is on a average year for decent ground. You also have to figure in all the crap ground that yields 90-110 bushels. That brings your average down quickly. I had some 235-240 bushel corn last year but it certainly didn't average that accross the whole farm. That far north are guys swiching to 20" rows? And by the way, I know I need to get back to the subject of wood/boilers. Just don't get too many farmers on this site.

 

[rowerwet]

try over at Iburncorn.com

 

[Jim K in PA]

try over at Iburncorn.com

Interesting site. Thanks for the link.

 

[Duetech]

S E Iowa,
I thought about using cob corn in my EKO so my wife could load the boiler but because of the clinkers I heard about form people with shelled corn burners I backed off and decided to go for smaller splits. I have two acres I could use to grow it but corn is also varmint food so storage comes in to play unless it's left on the stalk. But... I use and share this link a lot (broken link removed to http://www.chimneysweeponline.com/howood.htm) so according to them and according to the figures you are rummaging through 98 million btu (yield of cob corn per acre x 28k yield) is better than any 3 cords listed in the chart and I have been using black walnut and that comes out at a rough 4.8 cords converted and that is almost my winters use of wood. Even if I did a half acre it would give me a substantial source of renewable energy for not much more than my labor. I might just do up a half acre and buy my wife a wagon er with balloon tires of course. Well... she likes to walk. Oh yeah...pickin' 'n grinnin'. That's some good info...Thanks

 

[topofthehil]

cave,
I like your thinking.
cept the wagon part. my wife would not like to drag that through two feet of snow,
however, we have a Kubota that she likes to drive.
I could put extensions on the sides. that would give me a volume of 4' x 5' x 2' = 40 cu ft of corn.
40 cu ft / 2.5 cu ft per bu= 16 bu
16 bu x 70 lb per bu = 1,120 lbs (that's about the load limit of the Kubota)
we keep the Kubota in the shop with the Garn, so that would work out just fine.

 

[topofthehil]

Jim,
I did some more searching and found some more information on the BTU's of corn.
according to Penn state, a bu of corn, at 15.5 % moisture & 56 lbs, will generate a HHV (high heat valve) of 390,320 btu.
I am still looking for a cob corn btu valve, but I can't see it being any less BTUs than the shelled.
in the Garn example, they gave a value of 245,000 btu. they were off by 145,320 btu per bu.

here is the address:
http://energy.cas.psu.edu/energycontent.html

another good address for cost comparisons of various fuels is:
(broken link removed)

after looking at these charts, I figure, at my "today" costs, I would be slightly ahead burning corn.
however, I should note that I have an advantage over most people out there, as I have about 120 acres of woodland and another 80+ acres of ground to grow corn.
I would rather pick corn than cut, split haul and stack wood.
there's enough to do around here for exercise.

 

[Duetech]

Jim,
I did some more searching and found some more information on the BTU's of corn.
according to Penn state, a bu of corn, at 15.5 % moisture & 56 lbs, will generate a HHV (high heat valve) of 390,320 btu.
I am still looking for a cob corn btu valve, but I can't see it being any less BTUs than the shelled.
in the Garn example, they gave a value of 245,000 btu. they were off by 145,320 btu per bu.

here is the address:
http://energy.cas.psu.edu/energycontent.html

another good address for cost comparisons of various fuels is:
(broken link removed)

after looking at these charts, I figure, at my "today" costs, I would be slightly ahead burning corn.
however, I should note that I have an advantage over most people out there, as I have about 120 acres of woodland and another 80+ acres of ground to grow corn.
I would rather pick corn than cut, split haul and stack wood.
there's enough to do around here for exercise.

Maybe, with some testing, you could generate some interest for burning cob corn then generate the corn. Kind of a hobby income>Start small like 40 acres...tehe
Also it would be hard for me to have a kubota just for the wife to drive. Wonder what I would have to do to make me feel better about that??? snicker snicker.

 

[pybyr]

Hmm-- likely to get myself a grouch award here- but-

With biomass (actually any fuel) energy out is basically pretty closely related to density per unit volume

And for anything you grow or harvest, you need to "follow the BTUs (and $$$)" of your overall production/ processing cycle.

Last time I handled dried cob corn (and I have) its density per unit volume was a lot less than any cordwood I have handled.

And growing corn in any "modern" fashion involves:

buying seed

using mechanized (tractor plus planter) to plant $$$

using fertilizer and rotating crops (because you can't grow corn on the same soil/ area for endless years without really running the soil down) $$$

using (pesticides or cultivators to keep weeds out) (either way, use of energy) $$$

use of mechanized equipment to harvest/ shuck/ store/ dry (to prevent rot) $$$ (unless you have endless time to do a lot by hand)

compared with wood: trees grow; you cut them down, you split them up (all of which involves some, but, compared to crops, very modest energy/ $ / time inputs

I can see burning waste/ spoiled corn in those parts of the country where it is available and cheap.

I can't see growing corn as an intentional fuel source, even though I have 10-12 acres that would work for that purpose

 

[Duetech]

My endeavor would be small at about 1/2 or 1/4 acre for test purposes and I don't think it would be that expensive to initiate as there are sources readily available for seed and though I would not want junk, un-cracked feed corn will supply seed so I would not have to invest heavily in that regard. Even so "theoretically" one bag of seed could supply a lifetime of production if handled correctly. Storage can easily be had by leaving the ears on the stalk as many ears will bend down at full maturity. Labor wise the ears need not be shucked but merely cut from the stalk but the picking is another story. My wife and I already work about a 1/4 acre garden in the summer so I know what I am getting into with the cultivation and have some tools to make that approachable and I would rather ride a small tractor in the summer than try to work in the woods when it 85f. I have been burning mostly bl walnut and at the potential yield of 1/2 or 1/4 acre I might be able to supplement my winters heating needs by 25-50%. If it don't work reasonably I'm sure there are some critters hide the evidence.