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corn cob insulation

Dale Hodgins
pollinator

Joined: Jul 28, 2011
Posts: 4113
Location: Victoria British Columbia-Canada
    
  58
Has anyone attempted to make a cellulose insulation product from corncobs? I'm speaking of the dry woody cobs left after the harvest of mature cattle corn and not the soft easily rotted cobs from sweetcorn.

   After checking out wood chip clay insulation it occurred to me that ground corncobs covered in a clay slip should work as well. The big question is will weevils eat this material or is it rather inert like dry straw. Cellulose insulation is treated with Borax as a fire retardant and to make it unpalatable to vermin. It would seem the same process should work with ground corncobs. And since cobs are very light and airy they should give a better R-value.

   The beauty of corncobs is that they are a waste product which are gathered together in large quantities already so they would make a very cheap feedstock for anyone in the corn belt who needs to insulate.

   I'm thinking that clay slip insulation could be adapted to incorporate many agricultural waste products such as almond and peanut hulls, cotton waste or any other mostly cellulose byproduct which contains minimal nutrition for vermin. Mountains of this stuff buildup at processing facilities.

   Are there any corn farmers out there who have experimented with this or made any other product from corncobs?


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Nicholas Covey


Joined: Oct 09, 2008
Posts: 179
Location: Missouri/Iowa border
I have seen them stuffed into the attic space of an old farmhouse after they were (best I can tell) hammer-milled. I cannot attest to their ability or anything else about them other than they were there when the house was bulldozed and buried.

I don't think they were treated though due to the amount of rodent activity that was evident.

Also, I can tell you that most modern (ie GM Monsanto-ized) corn has a relatively small cob which tends to shatter into about 100 pieces when it's run through a combine. Mix that with the rest of the chaff and it's gonna be relatively difficult to get corn cob without getting corn stalk plus any weeds or whatnot that end up on the ground.
Andrea Wisner


Joined: Nov 18, 2011
Posts: 7
This might be helpful: http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1004&context=meep_articles&sei-redir=1&referer=http%3A%2F%2Fwww.google.com%2Fm%3Fq%3Dinsulating%2Bcob%2Brice#search=%22insulating%20cob%20rice%22
Experimental Determination of the Insulating Ability of Corn By-Products
Dale Hodgins
pollinator

Joined: Jul 28, 2011
Posts: 4113
Location: Victoria British Columbia-Canada
    
  58
Thank you Andrea. I like the idea of mixing it with cellulose insulation as discussed in the article. Cellulose already has vermin protection and fire protection built in. I've attempted to burn this material and it doesn't sustain a flame. It might be wise to tumble the chiped corncobs in diatomaceous earth prior to mixing with cellulose insulation. This would prevent weavil or other vermin from eating the material.
                        


Joined: Jul 07, 2010
Posts: 508
There has been work done in the Caribbean by a group (from Harvard?)who have turned corn cobs into charcoal to be used as an alternative fuel to take the pressure off the forests. They've figured out a way to make them burn, I think it involved making them into briquettes , so it is also a sort of small business opportunity I suppose. I don't remember the exact details, but seems to me they are taking the technology to other countries where wood is getting scarce for cooking fires. OTOH I couldn't swear as to what sort of corn cobs they are using, I would guess any they could get their hands on.

Aside from that, I think corncobs have also been hammermilled and used for bedding.

Don't see any reason why they wouldn't work as insulation if hammermilled and treated or mixed to make it less hospitable for vermin. Presumably this sort of corn will have less sugar in the cob than is the case with sweet corn.

Andrea Wisner


Joined: Nov 18, 2011
Posts: 7
Pellets for pellet stoves are made with corn cob as well as sawdust etc., right?

Interestingly, I was looking at this issue yesterday, and came upon information that corn stalks are now being used for biofuel, to save the actual food part of the corn for eating. I was specifically searching on "corn cellulose." So basically most of the corn stalk IS cellulose.

People are always looking for new uses for the corn plant. Of course, what we really need is to reduce corn agriculture and increase biodiversity. But for the corn that's there, might as well use all parts, right?

May be worth looking at the highest and best use of each part of the corn.
Andrea Wisner


Joined: Nov 18, 2011
Posts: 7
Actually I did a search and it sounds like they don't burn corn cob, which might bode well for its use as insulation. They do burn the corn itself mainly, and there was also reference to burning cubes made partly of corn stalks.

I did Google searches on verious terms:
corn cob pellets
corn cob stove (you can shorten to corn stove)
corn cob insulation.

There is a Wikipedia article that confirms that corn cobs are use for cellulose in cellulose insulation. I didn't read any farther than that.

EDIT: I should have searched "corn cob charcoal" too. Just did, and here is the article about a project at MIT (this one not Harvard): http://www.appropedia.org/Corn_Cob_Charcoal_Crusher. However, it doesn't sound great. They use carbonized corn cob, but not sure how they carbonize it - probably heat it to a high enough temp to melt any sugar inside which will turn to carbon. Then if you burn that carbonized cob, it will produce carbon monoxide. If you crush the carbonized cob and make briquettes of the dust, it doesn't produce carbon monoxide, but the dust in the manufacturing process is harmul to the lungs.

Sounds to me like a "last resort" source of heat. Haiti doesn't require heat for heating houses, so I'm assuming this is all used for cooking. Producing and distributing solar stoves might be more worthwhile. The sun is always available so fuel won't have to be constantly replenished.

EDIT AGAIN: BTW, I started looking at this when I discovered that "cob houses" are not made of corn cob, at all. I was a little disappointed. But then, not really. From Wikipedia: "Cob or cobb or clom (in Wales) is a building material consisting of clay, sand, straw, water, and earth, similar to adobe. Cob is fireproof, resistant to seismic activity,[1] and inexpensive. It can be used to create artistic, sculptural forms and has been revived in recent years by the natural building and sustainability movements."
Dale Hodgins
pollinator

Joined: Jul 28, 2011
Posts: 4113
Location: Victoria British Columbia-Canada
    
  58
I've burned corncobs in a wood stove and they tend to smoke. The problem could probably be alleviated by having good airflow, so I wonder if they would make a good feedstock for rocket stoves. -----Andrea, are you related to the Wisners of rocket stove fame? ----I wonder if anyone has tried putting corncobs through a rocket stove.

On the corn cob charcoal question, it would make sense to heat them up in an oxygen-poor environment as with the making of any charcoal.
                        


Joined: Jul 07, 2010
Posts: 508
http://www.ted.com/talks/amy_smith_shares_simple_lifesaving_design.html Sorry if that seemed a bit abrupt, hot chocolate got spilled on my keyboard and it reacted by instantly having several letters and the space bar quit working. It's taken this long to bring the laptop up to date! This link was the source of my info, not sure if there is later data or not.
stevo klopping


Joined: Oct 06, 2012
Posts: 1
We are currently building a bamboo framed community building in Northern Thailand and have the sane questions about this topic. We are experimenting using split bamboo verticals ( 5 cm. wide with 5cm. wide horizontal lathing at 5 cm spacing) and are wanting to fill the void with a clay and corn cob slip mix along with a rice straw to bind the matrix. We have been using a borate solution to treat the bamboos for powder post beetle and termite and will do the same with the cob. The local temple has started a clay/ cement brick making business to offset the new temple building cost and have as part of their equipment a very large clay and concrete mixing vat that we are hoping to rent for mixing the clay/ cob in large quantities for group usage . The rice and corn harvest is about two months away and I will be happy to keep you posted with the project.
The walls on the building e not load bearing and are mostly for insulation so we are not concerned the structural capacity . Good luck with your projects........
 
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