I live in the mountains in New Mexico planning my first cob house. After reading about cob for hours i walked outside and immediately noticed all the pine needles covering the ground. Could these replace or be added to straw in the cob mix? I assume i would have to mulch it or chop it in some way first.
I've heard of using wood chips, sawdust, twigs and of course straw, so I don't see why not and no, you shouldn't have to chop them as they are already a short length.
There are many others using Pine Straw (as it's called) in cob.
"You then add a fiber, usually rice straw or wheat straw, to add strength to the material that will eventually become your walls. I had a difficult time finding straw so decided to go with what I could find locally, pine needles, known in the south as pine straw. This same mixture can be put into a form and dried into bricks called adobe."
"Cob is a building material consisting of clay-heavy earth, water, sawdust, and pine straw. There are many recipes for mixing cob depending on where you are located and what is available to you. We use earth and pine straw from the Bosque, water from the rain, and sawdust from a local wood mill. The cob is mixed and then formed into walls, with spaces left for windows and doors. It is enjoyable to work with cob, mixing it with your feet and sculpting the walls."
"Miles Allen, a New Zealand architect working in earth building, had this to say, The cob buildings in New Zealand that have with stood earthquakes are those that are well built, the foundation should serve to protect the wall from RISING ground moisture. The straw in the wall acts a fiber to assist with stiffness but not as a structural reinforcement. In fact, the straw, pine needles, tussock stems, etc provide irrigation channels to allow the water to leave the earth wall evenly thus reducing shrinkage and significant cracking. Miles is currently involved in a project to write three earth building codes to cover five forms of earth building"
For more reading just google making cob using pine straw.
I have made a couple of test bricks with them and from what I can tell they work "ok". I have concerns about them because they have a waxy coating and they get decently brittle when dry. They are also kind of short so they wouldn't work as well as some long straw. They would work better for plasters where you are chopping straw anyways. But, I still have concerns about their becoming brittle and their waxy coating forming a poor key.
It's common, when making pottery, to add a small amount of lye when there is oil in the mix. It could be that a good cob recipe with pine needles would have a small amount of lye included.
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.