So I heard about this stuff a while back, and did not think much about it until recently. I was looking into ways to insulate the dome and was considering putting fiberglass insulation on the outside and another layer of shrink-wrap around that, or cutting foam panels into triangles and attaching them inside. Both options would be about $300. Being fundamentally cheap and since I am quickly running out of cash I decided to look into other options which brings us back to papercrete.
Basically this is like a large cement spitwad. You mix newspaper with water and blend it up into an oatmeal like slurry then you add portland cement powder. There are variations on the recipe, but the most basic seems to be equal parts by weight of dry newspaper to dry cement powder. You can pour this into blocks or molds or forms, or spray or plaster onto screens, or walls. One bag of cement will produce about 40 large blocks which will weigh about 3 lbs each. It apparently has an r-value (insulation) of about 2.5, by comparison the foam panels are about r-value:3. It is also basically fireproof and can be made waterproof by painting it with masonry sealer.
Any type of paper can be used, but newspaper is usually available for free in bulk from the local newspaper printing company or recycling center. The blocks are strong enough to drive over and will not shatter but will compress like a really stiff sponge. They can be made stiffer and more fireproof by the addition of more cement and sand with the trade off being greater weight and less insulation. Some people suggest adding borax to prevent mold and to further increase fire resistance.
The finished product can be cut with woodworking tools and will not fall apart even if it becomes wet. People have made ponds with this stuff. The real draw for me is that along with being practical and easy to work with, it is really cheap. The only thing you have to buy is cement and $10 worth of that will get you over 40 large blocks.
I plan to pour it into one inch sheets then cut into triangles to put on the inside of the dome. I have a batch drying at the moment and I made a small scale mixer out of a 55-gallon drum and a huge drill. I hope to make a tow-mixer this summer for making blocks, but this should get me through the winter at least. I will post more pictures of the test-blocks and the mixer later. I am currently testing different mixes portland / masonry cement / sawdust / polyurethane / leaves etc. The blocks in the picture are still very wet but quite hard, they have been drying for about 5 days now. Winter is probably not the best time to be doing this.