anyone ever burn "cob" corn in their Garn?

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: 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.

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

Click to expand...

How about a 15" chunk of wood?

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: .

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.

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.

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.

try over at Iburncorn.com

rowerwet said:

try over at Iburncorn.com

Click to expand...

Interesting site. Thanks for the link.

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 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 said:

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:
http://www.fpl.fs.fed.us/documnts/techline/fuel-value-calculator.pdf

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.

Click to expand...

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.

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

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.