leaf bales--a woodland substitute for straw bale construction material?

I recall that one of the wofatis has a small number of straw bales in one wall, and I had the idea come to mind today that if you had some kind of compressor similar to what makes compressed earth bricks but larger and less squeezy it might be able to bale up a bunch of leaves into something about the firmness of a straw bale.  Then you could use leaves instead of straw.  

I couldn't find a post about leaf bales on permies so I am posting here.  Does this exist? does such a machine exist? could someone build it? would a regular baler work or be retrofittable to do this? thoughts?

The hollow stalks in a straw bale are fairly stiff, and they are aligned mostly in the same direction. Bound tightly, that gives them a fair amount of inherent structural strength and also good insulating properties.

The leaf bale may have some other applications, but I don't think the strength would be there.

Down south I bought  pine straw (pine needles) in bales for mulch. Here in the PNW I don't see pine straw though I think Ponderosa's long needles might lend them to baling. Since our local building codes call for in-fill construction in straw bale structures the strength of the bales isn't an issue. Straw has few critters that eat it depending on the type of leaves would they have an interest to a critter of some kind?

Right.  Just the R-value?  It's good enough for a debris hut.

There's the issue of the "harvest" as well. With straw, the harvest and baling can be scheduled around the weather, avoiding the rain. Lots of leaves fall from the trees during rainstorms, and don't always get to dry out. You'd have to be pretty lucky or "on the ball" to get them at the "right time" or do some work to actively dry them.

Although, on the other hand, maybe damp leaves would compress better and retain their shape if then baked/kiln dried into a brick shape?

Wet or dry, leaves tend to be pretty slippery, layers sliding upon each other. Some form of "knitting together" of these layers would help. Punching partway through like those "no-staple" paper "staplers" that lock the sheets together by punching and forming tabs in them?

Maybe in the interest of drying, it might not be a brick or a bale, but more like a plate shape... maybe like a LEGO "plate-type" brick or like those wood fiber pallets that nest together. Each plate would be knit together and dried (maybe the same technology as the wood fiber pallets) and then the bumps would nest to align the plates together in all sorts of stacked configurations (just like LEGO bricks). Not sure the R-value of super compressed leaf bricks would be much better than wood however. It also turns it into a factory solution, not so much a woodland solution...

Maybe a leaf version of a gabion wall? Wire mesh basket to contain the leaves, either in a bale shape, or in a larger wall section. It would probably need some structure to support a roof. Even if not suitable for humans, it might make a good animal shelter. If kept dry under a good roof it might last more than one year with just a topping up. It could also be replenished each year, and the leaves used for bedding or mulch or compost.

I like Joshua's reference to debris huts. Good point. They work: I know that directly.

I would not hesitate to stuff bags of leaves into a temporary structure. They would work fine. I would arrange things so I could somehow visually monitor for incursions of rodents, at least. The rub, to my mind, is the more the leaves are compressed, the less air they hold and the less insulation they offer.

When we talk about straw, in volume, we are mostly talking wheat/oat/barley stalks from agricultural operations. Straw is tough, tubular, holds air in small pockets, and (as Kenneth said) is dried enough in the field to hold up over time. Mice will happily nest in it, given access. If consistently damp, the mold and fungi will start to break it down.

I also agree with Kenneth's suggestion that some composite mix of materials could make this a viable proposition. Maybe not in the exact form of a bale, but some sort of insulating sheet.

I haven't had problems with having leaves be too dry...I think that's a pretty solvable problem, put them out of the rain for a little while and they will dry out. I used leaves for mattress stuffing this past year, but I ended up buying straw for more volume and firmness.  (Ironically it was sold too compressed at the store, and I wasn't able to get to a farm to get some so had to buy Tractor Supply bales and then loosen them up a bunch).   Anyway, thanks for putting in some thoughts on this idea.  I think it would need to get tested out to know for sure.  

I had in mind that it would just be insulation, not structural support, so it needn't be too squished.

In digging around a bit I've found that R-value isn't the only factor to consider (in the sense that mold, moisture, settling affecting R-value, etc. are factors indpendent of "ahsolute" R-value under laboratory conditions/first test).  

And it seems that the looser the leaves the more insulative, up to a point.  Looser leaves will dry out faster if there's moisture, preventing mold.

Maybe the best bet would be to put a layer of thatch over the insulation to keep it from falling out, and still allowing some drying and air circulation.  Or some cloth sheets of some kind.

Maybe just raking a whole lot of leaves up outside the house in winter as a supplemental berm could be a short-term solution in a pinch...but leave it too long and it will certainly start molding and rotting the outside of your house.