In an ongoing quest for natural or sustainable construction materials, a formerly fringe building material called papercrete has become more popular in recent years. Also called fibrous cement or padobe, papercrete is a mixture of Portland cement, minerals, clay, water and a generous supply of waste paper products such as cardboard and junk mail. A large blender combines all of these ingredients into a thick slurry, or essentially an industrial grade paper mache.
The addition of a small amount of Portland cement, which acts primarily as a binder, does negate some of the environmental "greenness" of papercrete, but the paper fibers themselves would not provide much stability or strength as a building material. The papercrete slurry can be poured over forms or casts in the same manner as standard concrete, or it can be formed into large bricks like adobe or concrete.
Papercrete is not an ideal building material, but it can be created very inexpensively from readily available materials and used to build inexpensive and energy-efficient housing. Papercrete is 80% air, making it much lighter than standard concrete. It also has a fairly high insulation R-value, and the thickness of a papercrete wall also makes it noticeably soundproof. Papercrete can also handle several types of anchoring bolts and screws.
There are other advantages of papercrete to consider. The finished material can absorb substantial amounts of moisture without cracking or collapsing, making it a promising choice for roofing. The rainwater is absorbed into the papercrete during inclement weather, then released back into the atmosphere through evaporation as the roof dries. The bricks and forms can also be created by amateur builders with homemade equipment, another cost-saving advantage.
Papercrete does have some disadvantages, however. The material must be treated with a protective coating before it can be used to form walls or other exposed elements. Walls made of papercrete also tend to wick moisture from the ground, creating an ideal environment for mold growth. Papercrete is fire-resistant, but not entirely fireproof. It is so new as a "green" construction material, that there is little information on its long-term viability and safety. Continued exposure to the elements or aging of the materials used in its creation could create major problems for papercrete home owners 20 or 30 years in the future.
In short, papercrete does show a lot of promise as a safer and greener building material. Its current use seems to be limited to areas with little annual rainfall and very warm, dry climates, such as Arizona and New Mexico.