People have tried mixing concrete with all sorts of stuff; while it would be nice to do away with the energy consumptive production of concrete I doubt that will happen any time soon and it perhaps behooves us to try to instead minimize the use of concrete instead.

At a suitable extender matrix can be found, it might be possible to use only a third of the concrete for a given volume.

Let me state for the record I have no experience in construction, or concrete other than setting a couple of fence posts (only one of which worked I'd point out), I just read a lot. And of all the things I've read on this subject the one that impresses me the most is the concrete masonry idea where cord-wood is laid and the ends stuffed up with morter to make a very thick wood wall. An idea I hear from anybody that's done this is "build two walls".

So here's what I think somebody should try. Using standard concrete forms, use a mixture of 1/3 ground wood waste, where the size of each piece should be roughly the size of a golf ball although it shouldn't be that critical. 1/3 of the mixture could be chunks of Styrofoam (or it could be 2/3 wood waste).

Concrete and Styrofoam is already in use, the difference here is waste material us used.

This should work well, if made a bit wider than normal (but as long as it's less than 3X wider we come out ahead) for a single story. For taller structures, presumably the walls will be built in 4' courses and what might make sense is two use two walls with rebar (or scrap metal if you're really dedicated) laid on top on each course to stabilize the two; notches will have to be cur in the forms for the rebar.

I'd like to see somebody try this.