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Can I use Autumn Leaf litter in cob making?  RSS feed

 
James Hotchkiss
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Location: norther illinois
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So I am working my rear off raking all these leaves that come into my yard every year. I get to thinking, "what use can these leaves be other than to compost in the back yard?" I have been thinking of building a RMH for some time. I have everything in the house infrastructure that I need, I just need to locate raw materials. I was wondering if anyone has any experience making cob from leaf litter. The leaves that I have will keep piling higher and higher in the compost, and I sure don't mind the nutrient rich soil that they produce, but I am also looking for material that is readily available to create the cob for the RMH. Leaves seem to be plentiful. What do you all think?
 
Rebecca Norman
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Location: Ladakh, Indian Himalayas at 10,500 feet, zone 5
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Yep, we've tried that. We've built a lot of buildings out of rammed earth and also of lightly rammed earth we call packed earth, maybe it's like cob in formwork. We've been building and living in these houses for 20 years.

The past four years we've been experimenting with insulating materials mixed in, with either our usual mud-building mix, or a high percentage of straw/wood shavings mixed with a good sticky clay that we get from further away. We made one long room with the roof-bearing wall made of the mix packed in forms, and then we've also been making lots of large sort of adobe bricks. So, our experience is that with chopped straw or wood shavings, the result is hard and strong. But with autumn leaves, the result is crumbly.

For the insulating heat riser of a rocket stove, we used straw-mixed cob, and it has been working well for several months.

I think the leaves will be more useful for your compost and soil.

 
Jay C. White Cloud
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Hi James,

Rebecca has stated it perfectly!!! (excellent job Rebecca!)


Think of it this way James, if something works well in a compost heap...it really won't work well in the wall of a structure, as it just has to much "organic decomposable elements" in its interstitial matrix. This is why we can build a straw bale house, but can't (or at least shouldn't) build a hay bale house.

Good thinking of alternative uses and don't stop asking questions!

Regards,

j
 
James Hotchkiss
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Location: norther illinois
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Thanks Rebecca and Jay.

That makes sense. I have since been looking at a few sites where the permies are making briquets and "logs" out of the leaves using a binding agent like flour water. Once dried, they can be used for wood stoves and rocket stoves. Might be something that I try...

Have a great day!

Jamie
 
Glenn Herbert
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Location: Upstate NY, zone 5
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Even neglecting the "organic" part of leaves as a cob ingredient, they are the wrong shape to use in any kind of cob that wants to be strong. Straw pieces act as linear strings with the cob gripping at each point; flat leaves act like separators, keeping one part of the cob from interacting with another part. Even in kilns, where any organic matter will be burnt out completely, dried grass clippings work excellently as wet reinforcement and dry insulation, while leaves introduce weakness planes where the kiln wall can slip apart.
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